AWUS01 KWNH 232046
FFGMPD
TXZ000-240000-

Mesoscale Precipitation Discussion 0225
NWS Weather Prediction Center College Park MD
445 PM EDT Sun May 23 2021

Areas affected...south/southeast Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 232039Z - 240000Z

Summary...A persistent south-southeasterly flow regime will
continue to support showers and a few thunderstorms across the
discussion area this evening along with a risk of flash flooding.

Discussion...A persistent, deep south-southeasterly flow regime
continues between the southwestern periphery of a mid/upper ridge
centered over the Mid-South and a weak mid-level vort max centered
about 100 mi E of Brownsville. The flow pattern is continuing to
support a very moist, weakly buoyant airmass across the discussion
area with 2-2.2 inch PW values and 1000-1500 J/kg MUCAPE. The
airmass is weakly capped, and subtle lift associated with the
mid-level vort max and weak/subtle boundary layer confluence
continues to support areas of showers with embedded thunderstorms.
A couple of bands of heavier precipitation exist from near
Gonzales to Victoria, Texas and across the western Houston Metro
area, with enhanced rainfall rates of near 1-2 inches per hour
noted in the western-most band near Gonzales.

This persistent precipitation regime is expected to continue for
at least the next 3 hours or so as southeasterly low-level flow
maintains very moist low-level air and the mid-level vort max is
very slow to move. This will allow for occasional/isolated bands
of heavier precipitation to fall in areas that have received
abundant rainfall over the past week - exceeding 15 inches in a
few spots. The precipitation is resulting in wet soils and
correspondingly low flash flood guidance as a result (as low as 1
inch-per-hour thresholds near PSX/VCT). Additionally, showers and
isolated thunderstorms currently offshore (east of the mid-level
vort max) will migrate inland into the discussion area over the
next 2-3 hours. Most CAMs suggest a downtick in precipitation
rates after around 00Z or so, and the risk of additional flash
flooding will be re-evaluated around that time.

ATTN...WFO...CRP...EWX...FWD...HGX...

ATTN...RFC...WGRFC...NWC...

LAT...LON 30819714 30719608 30209510 29629472 29049495
28459619 28379715 28799794 29199814 29829821
30279811 30599783
$$
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AWUS01 KWNH 251918
FFGMPD
TXZ000-260115-

Mesoscale Precipitation Discussion 0236
NWS Weather Prediction Center College Park MD
317 PM EDT Tue May 25 2021

Areas affected...Eastern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 251915Z - 260115Z

SUMMARY...Showers and thunderstorms with heavy rainfall rates may
pose some flash flood threat over the next few hours.

DISCUSSION...The latest radar imagery shows a long-lived MCS now
bowing into areas of eastern TX. The airmass out ahead of this
over the broader southeast TX coastal plain is quite moist and
unstable with PWs of 1.8 to 2 inches and MLCAPE values locally
over 2000 j/kg. Meanwhile, a southerly low-level jet of 30 kts is
in place ahead of the MCS.

This favorable thermodynamic environment downstream of the MCS
suggests the ongoing activity will continue to expand off to the
east with some upside potential to expand in coverage and gain
greater convective organization given the additional
destabilization of the boundary layer that is expected over the
next couple of hours due to solar insolation.

Dual-pol radar QPE has already been suggesting some 1.5+ inch/hr
rainfall rates, and these rates should continue within the
stronger cells over the next few hours given the efficient
moisture transport pattern. The radar imagery also shows scattered
heavy showers and thunderstorms developing ahead of the main
complex within the moist/unstable low-level flow with locally
enhanced rain rates.

Over the next few hours, the southern portion of the long-lived
MCS may begin to slow its advance off to the east and may tend to
become oriented more southwest/northeast in nature such that
individual cells may begin to train over the same area. This
coupled with some cell-merger potential will tend to increase the
threat for some excessive rainfall totals going through the
late-afternoon and early evening hours.

The latest HRRR guidance suggests at least locally 3 to 4+ inch
rainfall totals going through 00Z. Given the wet antecedent
conditions, and heavy short-term rainfall rate potential, there
will be at least some concern for flash flooding.

Orrison

ATTN...WFO...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31999435 31759401 31279389 30589444 30069531
30079603 30289639 30439657 30589667 30799673
30999656 31409561 31949499
$$
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AWUS01 KWNH 271708
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-272305-

Mesoscale Precipitation Discussion 0245
NWS Weather Prediction Center College Park MD
105 PM EDT Thu May 27 2021

Areas affected...Northeast OK...Southeast KS...Southwest MO...Far
Northwest AR

Concerning...Heavy rainfall...Flash flooding likely

Valid 271705Z - 272305Z

Summary...Scattered areas of flash flooding will be likely across
portions of the Southern Plains this afternoon as deep convection
blossoms within a broad unstable warm sector. Hourly rainfall
rates of 2-3" are expected with 6-hr localized accumulations of
4-6 inches possible where convection trains.

Discussion...A broad warm sector characterized by MUCAPE of
2000-4000 J/kg, PWATs of 1.6-1.9 inches, and significant deep
layer moisture convergence will foster rapid upscale growth of
convection across the Southern Plains this afternoon as a potent
mid-level shortwave digs southeastward from the Northern Plains.
Semi-discrete thunderstorms will initially be relatively slow
(15-20 kts) with 2-3"/hr rainfall rates quickly saturating soils.
Much of the highlighted area is already in the 60-90th percentile
of 0-40 cm soil moisture (via NASA SPoRT Land Info System data),
indicating somewhat vulnerable antecedent hydrologic conditions.

Given that the latest high-res CAM guidance (including the HRRR)
has continued to handle convective trends rather poorly,
confidence in any targeted specific area is somewhat low. Where repeating/training of convection can occur 2-3" hourly rates will
rapidly translate to localized totals of 4-6 inches. Some
preference is given to northeastern Oklahoma to realize the
highest rainfall totals, but this area is also where 6-hr FFG is
the highest (3-5 inches). While southeast Kansas in particular has
the lowest FFG (2-4 inches), less repeating of convection is
likely as the advancing cold front cuts off avaliable instability.
That said, the combonation of a highly favorable mesoscale
enviorment and relatively poor hydrologic conditions make
localized flash flooding likely over the broader region.

Churchill

ATTN...WFO...EAX...ICT...LSX...LZK...OUN...SGF...TOP...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC...

LAT...LON 39059479 38889350 38389241 36129320 35379462
35469789 37119753 37999677 38519579
$$
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AWUS01 KWNH 311322
FFGMPD
TXZ000-311800-

Mesoscale Precipitation Discussion 0255
NWS Weather Prediction Center College Park MD
922 AM EDT Mon May 31 2021

Areas affected...North - Central Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 311321Z - 311800Z

Summary...Showers and thunderstorms developing along a cold front
will increase in coverage and intensity through late morning.
Rainfall rates are likely to exceed 2"/hr by the afternoon, and
training of these cells to the east could produce 2-4" of
rainfall. Flash flooding is possible.

Discussion...GOES-E IR imagery and the regional radar mosaic
depict cooling cloud tops and intensifying reflectivity indicative
of deepening convective development this morning. This convection
is blossoming along a moisture convergence axis associated with a
cold front that is being driven slowly southward on cyclonic flow
behind an MCV/surface low lifting through Oklahoma. This front is
sagging into a region of anomalous PWs and strong instability,
which will support continued thunderstorms, with both coverage and
intensity likely to build through early afternoon as the front
stalls across the region.

PWs as sampled by GPS observations and measured by 12Z U/A
soundings are 1.2-1.5", with 1.47" measured at KMAF. This is well
above the climatological 90th percentile, and is leading to
efficient rainfall production. The southerly LLJ is still analyzed
by VWPs and the RAP to be around 30 kts, which is impinging nearly
orthogonally into this front to drive ascent. However, this LLJ is
likely to veer and weaken over the next few hours. Despite the
less favorable LLJ position, this loss of ascent will be somewhat
offset by increasing instability through daytime heating and
continued mid-level lapse rates near moist adiabatic rates of
7C/km within a broad positively tilted trough. The combination of
the favorable thermodynamics and forcing through mid-level
impulses rotating through the flow is likely to drive waves of
thunderstorms today.

As the environment becomes more supportive, the HREF probabilities
indicate an increasingly likelihood for 2-3"/hr rain rates along
this boundary. The high-res guidance is struggling to handle the
ongoing convection which is leading to a wide variation in model
solutions over the next several hours. However, it is likely that
convection will develop and train over nearly the same areas along
the front due to propagation vectors and mean 0-6km winds aligned
to the boundary. Some of this area has received 2-3" of rainfall
this morning, leading to locally reduced FFG and higher soil
moisture conducive to rapid runoff and possible flash flooding.
While the highest HREF exceedance probabilities are progged later
today, these training storms, especially if they occur over the
pre-conditioned soils, could lead to flash flooding.

Weiss

ATTN...WFO...FWD...LUB...MAF...OUN...SJT...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON 34190066 34060000 34009936 33729888 33479873
33089883 32779924 32599997 32420054 32300123
32220193 32250261 32460287 32930296 33290288
33690275 34070212
$$
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AWUS01 KWNH 011904
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-012300-

Mesoscale Precipitation Discussion 0263
NWS Weather Prediction Center College Park MD
303 PM EDT Tue Jun 01 2021

Areas affected...Eastern TX...Southern AR...North/Central LA

Concerning...Heavy rainfall...Flash flooding possible

Valid 011900Z - 012300Z

Summary...Showers and thunderstorms will continue to blossom
across eastern TX into southern AR and much of LA through the
afternoon. Some of this activity will be slow moving and with the
potential for training over the same areas. Therefore, rain rates
in excess of 2 inches/hour are possible with areal average
rainfall of 2-4+ inches possible through the next six hours.
Antecedent conditions combined with high resolution model signals
suggest flash flooding is possible.

Discussion...A mid/upper level trough across the central U.S. will
continue to provide modest divergence aloft. This combined with
shortwave activity (including an eastward advancing MCV in
northeastern TX) will lead to large scale forcing for ascent. In
response, rich Gulf moisture will be pulled north into eastern TX
and the Lower MS Valley region ahead of a stationary surface
boundary. As a result, precipitable water values of 1.5-1.75
inches will expand east and increase with strong WAA. Despite
morning cloud debris from earlier convection, MUCAPE has already
climbed above 2000 J/kg with additional destabilization expected
over the next several hours. Given these factors, anticipate
convection will continue to develop and blossom within this
region. Based on the propagation vectors and mean wind,
anticipate convection to be slow moving initially with the
potential for brief training. It should also be noted that with
weak shear of around 25 knots, highly organized convection is not
expected but possible across portions of eastern LA by later this
afternoon. According to high resolution guidance, rain rates may
exceed 2 inches/hour with areal average precipitation of 2-4+
inches within the next six hours. This is supported by the higher
HREF probabilities.

While flash flood guidance values within this region are fairly
high (3-5 inches in 3 hours), portions of the ArkLaTex region has
observed above normal precipitation over the past week along with
slightly above normal soil moisture within the scalloped region.
Therefore, scattered flash flooding may occur.

Pagano

ATTN...WFO...HGX...JAN...LCH...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34449293 33279115 31199173 30109333 30069533
30649632 31599495 33329448
$$
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AWUS01 KWNH 031556
FFGMPD
VAZ000-NCZ000-SCZ000-032154-

Mesoscale Precipitation Discussion 0270
NWS Weather Prediction Center College Park MD
1155 AM EDT Thu Jun 03 2021

Areas affected...NC/SC

Concerning...Heavy rainfall...Flash flooding possible

Valid 031554Z - 032154Z

Summary...Convection is rapidly expanding in coverage across
portions of the Carolinas, with isolated to scattered flash
flooding possible through the afternoon hours.

Discussion...Broadly confluent flow in the low levels, along with
the upper trough to the west and a subtle wave moving into the SC
coast are all helping initiate convection across SC/NC. The
scattered to widespread nature of convection will probably cap the
amount of destabilization possible...although still looking at
1000-2000 J/kg of CAPE, certainly sufficient for deep convection.
PWs are approaching 2", which is getting close to the early June
maximum expected values. Merging moisture plumes, one in the
mid/upper levels associated with the approaching trough, and the
other in the lower levels off the Atlantic, are supporting the
deep moist profiles. The combination of high PWs, high wetbulb
zero heights, and thin CAPE profiles certainly supports efficient
rainfall in any heavier cells through the afternoon hours.

The area is currently in drought conditions, although heavy rain
yesterday has saturated the top levels of soil in parts of the
region...while the deeper soil anomalies generally remain below
average. So while the region could generally still use more
rain...the saturated top layers of soil should help increase
runoff today resulting in isolated to scattered instances of flash
flooding. Cells will be quick moving off to the northeast, but
unidirectional flow supports some small linear training segments,
and some repeat of cells through the afternoon given the scattered
to widespread nature of convection.

Thus while a more widespread/organized convective complex seems
unlikely, the above ingredients should be enough to still result
in pockets of flash flooding through the afternoon hours. Urban
and low lying areas will be most susceptible...but some flash
flooding is possible wherever todaty's heavier totals overlap with
yesterdays.

Chenard

ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON 36737652 36407642 35557699 34747755 34497808
34047898 33587939 33427980 33358015 33588039
34218065 34718054 35757932 36517791
$$
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AWUS01 KWNH 081557
FFGMPD
MAZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-082156-

Mesoscale Precipitation Discussion 0300
NWS Weather Prediction Center College Park MD
1157 AM EDT Tue Jun 08 2021

Areas affected...northeastern Pennsylvania into southern New York
State

Concerning...Heavy rainfall...Flash flooding possible

Valid 081556Z - 082156Z

Summary...Slow-moving storms will pose a risk for isolated flash
flooding through the afternoon and early evening in and near the
discussion area.

Discussion...A slow-moving cluster of convection has evolved in
northeastern Pennsylvania over the past hour or so, with areas of
towering cumulus across much of the discussion area from
southeastern Pennsylvania to western Massachusetts. The storms
are in an environment characterized by weak, but westerly vertical
shear and very strong instability (as high as 4000 J/kg SBCAPE in
areas downstream of ongoing storms). The pre-convective airmass
is quite moist also, with PW values of 1.6 to 1.9 inch areawide.
Lift from an approaching shortwave trough across central PA/NY and
weak/subtle boundary layer confluence was also providing ascent
aloft for thunderstorm development.

Latest observations/guidance suggests that this mainly diurnally
driven convective activity will continue to expand in coverage
this afternoon. Local rainfall rates of 1-2 inches per hour have
already been observed beneath convective cores, and this will
expand in coverage with time - especially as storms form mature
cold pools and propagate slowly eastward. Flash flood guidance
values are in the 0.75-1.5 inch-per-hour range, which should be
easily exceeded beneath heavier convective cores/clusters. The
threat should wane some after sunset with loss of
heating/surface-based instability.

Cook

ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 43057325 42817261 42157246 41557285 40927380
40337472 40037588 40107668 40307712 40607717
42347608 42697525 43017412
$$
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AWUS01 KWNH 081646
FFGMPD
NDZ000-082244-

Mesoscale Precipitation Discussion 0301
NWS Weather Prediction Center College Park MD
1245 PM EDT Tue Jun 08 2021

Areas affected...North Dakota

Concerning...Heavy rainfall...Flash flooding possible

Valid 081644Z - 082244Z

Summary...Areas of flash flooding are expected to continue through
the afternoon across the discussion area.

Discussion...A complex convective evolution continues to unfold
across central North Dakota, with slow westward propagation of
convection associated with storms along a synoptic warm front now
nearly stationary just east of the Bismarck area. One complex in
particular (centered over Kidder County) is nearly stationary
while producing estimated 1-3 inches of rainfall in an hour.
These rainfall values will readily exceed the 1.5-2.5
inch-per-hour flash flood guidance thresholds across the region,
promoting a continued risk of flash flooding there.

The complex evolution lends some uncertainty with respect to
evolution of the convection over the next 6 hours or so. The
presence of a weak shortwave trough just west of the region and
convergence along the warm frontal zone will continue to foster
development of new convection near the initial complex and these
cells may also move slowly northward, backbuild, and/or stall.
Additionally, as the warm front lifts slowly northward, the axis
of focus for development may also shift northward (as suggested by
the latest runs of the HRRR), with potential for heavy rainfall
and isolated flash flooding extending northward/northwestward over
the next 3-6 hours or so. Flash flood guidance values are
slightly lower in western and northern North Dakota (around 1"/hr)
compared to near Bismarck (1.5-2.5"/hr). It is possible that
stronger convection (with heavier rainfall) remains rooted closer
to the warm front through the afternoon where stronger
instability, lesser inhibition (in the 700-850mb layer), and more
focused surface convergence resides.

Cook

ATTN...WFO...BIS...FGF...

ATTN...RFC...MBRFC...NCRFC...NWC...

LAT...LON 48550059 48189930 47349867 46439904 46180027
46390191 46960272 47410284 48110253 48410182
$$
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AWUS01 KWNH 081911
FFGMPD
OHZ000-MIZ000-INZ000-082315-

Mesoscale Precipitation Discussion 0302
NWS Weather Prediction Center College Park MD
311 PM EDT Tue Jun 08 2021

Areas affected...Northwest OH...Northeast IND...Ext Southwest MI.

Concerning...Heavy rainfall...Flash flooding possible

Valid 081910Z - 082315Z

SUMMARY...Slow moving cells and deepening moisture profiles
support localized heavy rainfall and potential for flash
flooding...

DISCUSSION...GOES-E WV suite denotes older shortwave/closed low
feature over the Tri-State area of S MI/NW OH/NE IND. Given its
placement in the larger scale pattern, upper level flow is
favorable for solid diffluence to support the developed convection
in/east of the UL proper. CIRA LPW suite also denotes moisture
entering the low to middle profile of the cells to further enhance
the rainfall efficiency, resulting in 1.75 to 1.9" of total
moisture in the column. Entrainment with 15-20kts of flow through
85-7H brings rates to 2-2.25"/hr, though equally allows for slow
cell motions and with upstream inflow and upstream propagation to
further slow motions. Strongest overshooting top near Hancock
county, OH seems to be ideally situated for this combination of
favorable upper-level divergence to show signs of building back
against the flow slightly. Development is enhanced by solid low
level convergence along Lake enhanced boundaries intersecting with
the weak northward march of the higher Td air from the
Ohio/Mississippi Valleys.

While the area is generally below average in the longer terms...
there is lower FFG values across the area of concern which aligns
with with AHPS 2-week anomalies near to 200% of normal. Hourly
FFGs of 1-1.5" and 3hr values of 1.5-2.5" have solid potential to
be exceeded with these cores. But given the nature of the complex
overall coverage should be scattered in nature and will dissipate
with reducing instability into the evening. As such, flash
flooding is considered possible but local thunderstorms of 2-3"
totals in 1-2 hours or even sub-hourly per report near Vermilion.

Gallina

ATTN...WFO...CLE...DTX...ILN...IWX...

ATTN...RFC...NCRFC...OHRFC...NWC...

LAT...LON 42358328 41698290 41558155 41128142 40638193
40448272 40538339 40938435 41008536 41398551
41748465
$$
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AWUS01 KWNH 091505
FFGMPD
TNZ000-ALZ000-MSZ000-ARZ000-092102-

Mesoscale Precipitation Discussion 0312
NWS Weather Prediction Center College Park MD
1104 AM EDT Wed Jun 09 2021

Areas affected...northern Mississippi, eastern/southeastern
Arkansas, northwestern Alabama

Concerning...Heavy rainfall...Flash flooding likely

Valid 091502Z - 092102Z

Summary...Areas of flash flooding remain likely across the
discussion area through at least 21Z. Significant impacts are
expected given extreme antecedent rainfall over the past 24 hours.

Discussion...Recent radar mosaic imagery indicates several bands
of slow-moving/propagating convection across the discussion area -
particularly in eastern Arkansas, northern Mississippi (near
Oxford), and northern Alabama (northwest of Birmingham). The location/orientation of these bands isn't particularly surprising
given broadly confluent westerly/southwesterly 850mb flow
partially orthogonal to a weak low-level boundary from near Little
Rock to near Tupelo. The low-level flow was maintaining a moist,
destabilizing pre-convective airmass across the region
(characterized by 2-inch PW values, nearly 2000 J/kg MUCAPE, and
minimal convective inhibition). The moisture and instability was
promoting rainfall rates of up to 3 inches per hour beneath
heavier thunderstorm cores which easily exceed FFG thresholds in
the region - especially in eastern Arkansas and northern
Mississippi where widespread areas of 3-10 inches of rainfall were
observed yesterday. Impressive MRMS Flash responses have already
been noted this morning in east-central Arkansas and near Oxford,
Mississippi.

Though the general axes of convergence are less focused compared
to yesterday, models/observations generally suggest that bands of
heavy rainfall will continue to propagate slowly
eastward/east-southeastward resulting in very heavy rainfall and
additional accumulations of at least 2-4 inches (locally higher)
through 2030Z. Models also indicate initiation of convection
south of these bands, which isn't surprising given the strong
destabilization occurring there. Localized training of convection
is expected in this regime (which may already be materializing in
east-central Arkansas). Convective mergers may also allow for a
slow, more southward component to MCS motions during the period as
well, allowing for heavier precipitation to eventually shift
toward the US82 corridor in Mississippi. Each of the
aforementioned factors point to locally significant flash flooding
especially beneath heavier/training convection.

Cook

ATTN...WFO...BMX...HUN...JAN...LZK...MEG...OHX...

ATTN...RFC...ABRFC...LMRFC...SERFC...NWC...

LAT...LON 35068996 35018783 34828659 34608618 34118614
33568659 33268805 33139020 33109190 33399234
34059232 34689205 34949122
$$
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AWUS01 KWNH 091739
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-092337-

Mesoscale Precipitation Discussion 0314...Corrected
NWS Weather Prediction Center College Park MD
138 PM EDT Wed Jun 09 2021

Corrected for Areas Affected Header

Areas affected...northeastern Ohio, Pennsylvania, and far southern
New York State.

Concerning...Heavy rainfall...Flash flooding possible

Valid 091737Z - 092337Z

Summary...Convection drifting slowly southward across the
discussion area could pose a very localized/isolated flash flood
risk through peak-heating hours..

Discussion...Satellite/lightning imagery indicates scattered
thunderstorms across the discussion area that were moving slowly south-southwestward. The cells were in an environment
characterized by very weak vertical wind shear (with northerly
flow around 10 knots or so from the surface to 300mb), moderate
instability (around 2000 J/kg MLCAPE), and PW values ranging from
1.3-1.7 inch. These conditions are conducive for brief heavy
downpours with as much as 1 inch per hour of rainfall in a few
spots. FFG values of around 1.5 inch-per-hour rainfall rates
(slightly lower in southern New York State and southwestern
Pennsylvania) suggest that a brief/isolated flash flood risk will
exist - particularly in areas where heavier rainfall occurs over
flood-prone or hydrophobic surfaces (i.e., urban areas and hilly
terrain). This risk should be mainly dirunally driven and lessen
after sunset.

Cook

ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 42317939 42297756 41927676 41567661 40907664
40347684 39847756 39977979 40688129 41208142
41688113
$$
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AWUS01 KWNH 101620
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-102215-

Mesoscale Precipitation Discussion 0321
NWS Weather Prediction Center College Park MD
1219 PM EDT Thu Jun 10 2021

Areas affected...portions of the northern Mid-Atlantic region

Concerning...Heavy rainfall...Flash flooding likely

Valid 101616Z - 102215Z

SUMMARY...Slow moving thunderstorms are expected to increase in
coverage across the northern Mid-Atlantic region this afternoon.
Rainfall rates of 1-2 in/hr will be common, but locally higher
rates can not be ruled out.

DISCUSSION...Visible satellite imagery through 1545Z showed an
expanding cumulus field within an otherwise mostly clear
environment across the Delmarva Peninsula into MD and southeastern
PA. A few showers and thunderstorms have also popped up on
regional radar imagery over northern Delaware Bay and along the
Catocin Mountains of northern MD into the Appalachian chain of
southern PA. PWATs within the pre-convective environment are 1.7
to 2.0 inches and 850-200 mb mean-layer flow is very weak across
the entire region at less than 10 kt, which will support slow
storm motions. Little CIN on the 12Z soundings from WAL and IAD
suggest storm coverage will continue to increase with daytime
heating with the front and local terrain acting as sources for
lift. In addition, locally stronger easterly flow just behind the
cold front may help to support near-stationary convection along
the terrain of northern VA into northwestern MD and southern PA.

Given the lack of speed shear with height, storms should not be
organized in nature or long-lasting, but they should be rather
efficient with rainfall production given high wet bulb zero
heights of roughly 13 kft. Rainfall rates of 1-2 in/hr are very
likely with localized rainfall rates up to 3 in/hr possible. In
fact, rainfall rates from the HRRR support 1-2 inches of rain in
15 to 30 minutes which seems reasonable given the moist
environment. Portions of the Delmarva into southern MD and
southeastern PA received heavy rainfall yesterday and will be more
susceptible to localized flash flooding today. While flash
flooding is not expected to be widespread across the entire
region, scattered to numerous slow moving thunderstorms will
produce heavy rainfall with several areas at risk for flash
flooding, including the urban I-95 corridor from south of D.C.
into northern DE with 2-4 inches expected through 22Z.

Otto

ATTN...WFO...AKQ...CTP...LWX...PBZ...PHI...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40587854 40517767 40357679 40047594 39547543
38187496 37767548 37877657 39167880 39907971
40507942
$$
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AWUS01 KWNH 101727
FFGMPD
MSZ000-LAZ000-ARZ000-102315-

Mesoscale Precipitation Discussion 0322
NWS Weather Prediction Center College Park MD
127 PM EDT Thu Jun 10 2021

Areas affected...central AR into northeastern LA and central MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 101722Z - 102315Z

SUMMARY...Backbuilding and training convection is expected to
continue areas of flash flooding for central MS and northeastern
LA, expanding northwestward into central AR through early evening.
Peak rainfall rates of 2-3 in/hr should continue and the overlap
with recent areas of heavy rain will exacerbate ongoing flooding.
An additional 3-5 inches is forecast through 23Z.

DISCUSSION...A long-lived complex of thunderstorms over the Lower
Mississippi Valley has shown a slow evolution over the past 6
hours toward the south and west. Low level cloud elements on
visible imagery continue to show a confluent pattern into the
tri-state region of AR/LA/MS where MRMS rainfall estimates ending
at 17Z have been near 4 in/hr in Issaquene County. A lack of
rainfall observations in the area has made it difficult to confirm
MRMS estimates, but the history of this complex and the efficient
environment make the MRMS rates seem reasonable. MLCAPE estimates
as of 17Z show 2000-3500 J/kg over northern LA into central AR
where mostly clear skies have allowed surface temperatures to
climb into the upper 80s while dewpoints are in the mid to upper
70s.

While winds at 850 mb have weakened since earlier this morning
into the 10-20 kt range, similar strength and direction of the
850-300 mb mean flow has supported backbuilding of storms into
southeastern AR. Short term forecasts from the RAP have been
consistent with maintaining the current strength and direction of
the low and mid-level flow into the early evening. Therefore, weak
to locally moderate low level confluent flow within the moist
environment and the presence of the right-entrance region of a
40-60 kt upper level jet streak to the north should continue to
support convective development over the next several hours.

Ongoing training near the LA/AR/MS junction may weaken in the next
2-3 hours in favor of increasing development into a expanding
cumulus field over central AR. The greatest confidence for an
additional 3-5 inches of rain exists across far western MS into
northeastern LA and southern AR, while convection to the north
(centarl AR) is expected to be more scattered in nature with
rainfall rates of 1-2 in/hr. Given heavy rain over the past 3
days, additional any added heavy rain will only worsen ongoing
flooding concerns.

Otto

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 35689213 35289148 34019055 33468979 33018917
32418911 32098970 32089100 32769240 33579289
34879299 35589275
$$
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AWUS01 KWNH 101802
FFGMPD
MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-102300-

Mesoscale Precipitation Discussion 0323
NWS Weather Prediction Center College Park MD
201 PM EDT Thu Jun 10 2021

Areas affected...WV...southwest OH...Western & Southwestern VA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 101800Z - 102300Z

SUMMARY...Slow/Chaotic motions but ample deep warm cloud layer for
efficient rainfall through complex terrain.

DISCUSSION...GOES-E WV and Visible suite depict a vertically
sheared cyclone with 6.2um channel centered over western VA, 7.3
over central WV and IR/VIS channels showing compact center into
southwest OH. As a result, there is weak chaotic flow regimes,
though low level through 7H suggests southwesterly moist flow
across E WV into the front ranges of the Appalachians in western
VA and this is denoted well in the 850-7H Layer PW from CIRA.
Being on the western periphery of the upper-level waves has
supported some additional clearing for ample isolation and
building of instability. Mtn/Valley circulation combined with
some low level mass piling is supporting increasing agitation of
cu field both under the best mid-level cooling/upper-low but also
along the southeast quadrant of the lower circulation along/near
the Ohio River. Mid-level cloudy conditions have all but rendered
areas across far N WV into the western MD/Eastern WV panhandle
less conducive.

Deepest convective elements are forming with the better mid-level
lapse rates along the terrain of far E KY into W VA. Still, due
to deep warm cloud layer, ample moisture individual cells will be
highly efficient with up to 2"/hr rates. Cell motions will be
near zero further north and west with 5-10 kts toward the NNE
across southern portions of the MPD area. Hi-Res CAMs all suggest
best scattered 2-2.5" totals over E WV into W VA with the slightly
better 5-10 kts of inflow to help maintain updrafts more than the
"up and splat" nature further north and east,
propagating/regenerating along the outflows.

Still both modes have solid potential to exceed the low FFG in
complex terrain which is about 1"/hr though lower values of
.5-.75"/hr are nearer the low level cyclone convergence point.
Flash flooding is likely though it will be highly
scattered/locally focused to only a few watersheds...where some
neighboring watersheds may miss out totally.

Gallina

ATTN...WFO...JKL...LWX...MRX...PBZ...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 39598200 39578099 39458008 39277949 39047903
38157928 37377979 36738086 36788232 37348272
38158231 39158235
$$
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AWUS01 KWNH 191721
FFGMPD
FLZ000-GAZ000-ALZ000-192318-

Mesoscale Precipitation Discussion 0355
NWS Weather Prediction Center College Park MD
120 PM EDT Sat Jun 19 2021

Areas affected...southeastern Alabama, Florida Panhandle, and
southwestern Georgia

Concerning...Heavy rainfall...Flash flooding likely

Valid 191718Z - 192318Z

Summary...Slow-moving convection on the southeastern periphery of
Tropical Cyclone Claudette will continue a risk of flash flooding
especially in the Florida Panhandle and vicinity through 00Z.

Discussion...Most of the heaviest convection on the southeastern
periphery of Claudette has been confined to one or two dominant
convective bands over the past 6 hours or so. The bands are
focused along a strongly confluent low-level wind field, which has
supported ascent within a very moist (2.2+ inches PW) and unstable
(2000+ J/kg MLCAPE) environment, allowing for areas of 2-3.5
inch-per-hour rainfall rates at times. The bands have produced
widespread areas of 2-5 inches of rain and isolated amounts as
high as 7.5. The highest amounts have so far been confined to
land areas nearer the stronger instability (located within 100 mi
of the coast and areas offshore).

These trends should continue through the evening hours.
HRRR/HREF/Nam and other guidance suggests that at least one or two
bands of convection should persist or gradually become more
elongated from southwest to northeast across the discussion area.
The localized training of convection will continue to allow for
widespread heavy rain to shift eastward, with many areas of 2-5
inch rainfall (and locally higher amounts) to occur across the
discussion area. The rainfall rates have overwhelmed flash flood
guidance (especially in flood-prone areas) and resulted in flash
flood impacts - especially in the Pensacola area recently.

Cook

ATTN...WFO...BMX...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32648425 32248332 31328294 30888307 30418348
30178409 29738512 29638587 30128700 30968719
31748690 32298635 32508549
$$
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AWUS01 KWNH 192023
FFGMPD
ILZ000-MOZ000-200112-

Mesoscale Precipitation Discussion 0356
NWS Weather Prediction Center College Park MD
423 PM EDT Sat Jun 19 2021

Areas affected...PORTIONS OF EASTERN MISSOURI AND WESTERN
ILLINOIS...INCLUDING THE ST LOUIS METRO AREA

Concerning...Heavy rainfall...Flash flooding possible

Valid 192012Z - 200112Z

Summary...A west-northwest to east-southeast area of back-building
convection along an axis of favored low-level frontogenesis will
result in an enhanced risk of flash flooding through 01Z.

Discussion...At 20Z, a surface cold front was draped across
northern Missouri and northwest Illinois. With the uptick in
pre-frontal south-southwesterly flow in the lower levels, the
airmass south of this front continues to destabilize this
afternoon as per satellite and radar trends, particularly across
portions of northeast and east-central Missouri where mixed-layer
CAPES average between 3000-4000 j/kg per the latest SPC
mesoanalysis. At the same time, the deep-layer moisture pooling is
also helping to raise PWAT values (1.6 to 1.8+ inches currently).

Albeit subtle, the position of the outlook area southwest of a
departing northern stream shortwave is resulting in weak
divergence aloft, with the focused area of deep-layer lift and
low-level frontogenesis aiding to the initiation of convective
clusters across portions of northeast and eastern Missouri into
western Illinois. As the afternoon progresses, the convection is
expected to grow upscale and expand across the outlook area,
particularly across portions of northeast and eastern Missouri
along the axis of greatest deep-layer instability. Given the
favorable thermodynamical environment, hourly rainfall rates of
2-2.5 inches are anticipated underneath the strongest cells, which
may lead to localized flash flooding, particularly in urban and
other areas prone to flash flooding. The latest CAM guidance
indicates pockets of 3-5" totals through 01Z over the outlook
area. Given the likely expansion of the convection upstream
(toward the axis of maximum instability), along with the
southeasterly storm motions, some cell training is expected,
thereby giving credence to these higher amounts indicated by the
CAMs.

Hurley

ATTN...WFO...ILX...LSX...PAH...

ATTN...RFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 39819149 39729003 39348896 38488894 38028992
38399102 38999196 39559205
$$
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AWUS01 KWNH 201001
FFGMPD
FLZ000-GAZ000-ALZ000-201500-

Mesoscale Precipitation Discussion 0364...Corrected
NWS Weather Prediction Center College Park MD
601 AM EDT Sun Jun 20 2021

Corrected for Changed Areas Affected

Areas affected...Florida Panhandle, Southeast AL, Southwest GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 200951Z - 201500Z

Summary...Expanding coverage of thunderstorms in warm advection
ahead of an MCV will create an increasing flash flood risk this
morning. Multiple rounds of convection with rain rates to 2"/hr
are possible. Rainfall of 1-3" with isolated higher totals is
expected.

Discussion...A potent MCV stemming from a long-lasting forward
propagating MCS which has raced eastward overnight is now lifting
E/NE east of Hastings, NE. This MCV is being driven in part by a
robust and amplifying mid-level shortwave, and is moving into a
tropical airmass characterized by PWs around 1.5" and MUCape of
1500-2500 J/kg. A stationary front was analyzed draped west to
east along the MO/IA border, and recent VWPs indicate the 850mb
LLJ is increasing to 25-35 kts from the SW. This low-level SW flow
is isentropically ascending the stationary front, leading to
locally enhanced ascent across the region.

As the MCV continues to move eastward, ascent through PVA ahead of
the parent shortwave, isentropic upglide, low-level convergence
along the nose of the LLJ, and some enhanced acceleration east of
the MCV should maximize into the favorable thermodynamics. Recent
reflectivity from KEAX and KOAX indicate convection expanding
rapidly within the WAA regime and organizing due to bulk shear of
25-35 kts, with radar-estimated rainfall rates of 1-2"/hr becoming
common. While mean 850-300mb winds are robust to the E/NE at 20-30
kts, several rounds of heavy rainfall are possible during the next
few hours.

The HREF hourly rain probabilities suggest rainfall rates of 1-2"
will remain common through 12Z before beginning to wane as the MCS
moves into subtly drier air and the LLJ begins to veer, weakening
the ascent. During this time, rainfall of 1-3" is likely in many
locations as shown by the high-res guidance, and 6-hr HREF EAS
probabilities for 1" are above 60%, indicating both the agreement
of the members and the potential for excessive rainfall. While
recent rainfall has been modest during the past 14-days leading to
drier than normal soil moisture, there have been pockets of
rainfall 150% of normal during this time frame in SW IA. Here, FFG
is locally reduced to 1.5-2"/3hrs, and exceedance probabilities
are as high as 50%. Isolated flash flooding is possible through
early morning, but is most likely should this heavy rainfall occur
atop these locally more saturated soils.


Weiss

ATTN...WFO...BMX...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32888426 32808366 32508303 32078261 31648242
31058232 30588228 30238243 29958259 29708287
29528332 29428379 29448447 29498495 29668553
29878601 30138625 30498637 31068626 31558597
32118552 32568511 32778480
$$
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AWUS01 KWNH 201923
FFGMPD
NCZ000-SCZ000-210122-

Mesoscale Precipitation Discussion 0366
NWS Weather Prediction Center College Park MD
323 PM EDT Sun Jun 20 2021

Areas affected...portions of North and South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 201922Z - 210122Z

Summary...Gradually increasing convective coverage could result in
a few areas of flash flooding this afternoon and evening.

Discussion...Ahead of the eventual path of TD Claudette, strong
insolation amid a moist and increasingly buoyant airmass
(characterized by 2-2.3 inch PW values and around 2000 J/kg
MLCAPE) was fostering robust convective development recently. The
storms are in an environment with southwesterly flow aloft and
were moving northeastward at around 15-20 knots. However, the
weak low-level confluence and orientation of the development was
allowing for convection to repeat/develop in areas that have
received around 1-3 inches of rain earlier and have FFG values
ranging from 1-2 inch-per-hour thresholds. The very moist airmass
was allowing for rainfall rates to exceed these thresholds beneath
the heavier updrafts (up to around 2.5 inches per hour at times),
suggesting that at least a spotty flash flood threat should
materialize especially wherever training convection can occur.

Over time, convective coverage should continue to increase through
at least sunset due to continued insolation and low-level
convergence ahead of Claudette. There may be a downtick in
convective coverage thereafter due to loss of insolation, although
the moist environment should still sustain a few lingering storms
after sunset especially where updrafts can ingest non-convectively
modified air.

Cook

ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...

ATTN...RFC...SERFC...NWC...

LAT...LON 36507687 35757645 35247670 34627730 33947811
33447893 32747988 32568062 32898137 33258164
34078207 34768161 35558024 36197842
$$
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AWUS01 KWNH 211917
FFGMPD
VAZ000-WVZ000-OHZ000-TNZ000-KYZ000-220116-

Mesoscale Precipitation Discussion 0371
NWS Weather Prediction Center College Park MD
316 PM EDT Mon Jun 21 2021

Areas affected...Central/Eastern Kentucky...Central Appalachians

Concerning...Heavy rainfall...Flash flooding possible

Valid 211916Z - 220116Z

Summary...Training thunderstorms along and ahead of a cold front
will be capable of producing hourly rain totals of 1-2" at times
and could lead to flash flooding across portions of the lower Ohio
Valley and central Appalachians through early evening.

Discussion...Large scale forcing for ascent provided by the
approach of a shortwave trough is focused over portions of the
lower Ohio Valley into the central Appalachians this afternoon. At
the surface, a seasonably strong cold front is analyzed generally
along/north of the Ohio River. The environment ahead of this
feature is very warm and moist, characterized by dewpoints in the
lower to middle 70s with a recently GPS analyzed PW of 1.6-1.8".
There is more than sufficient amounts of instability available
given both the surface heating and low/mid level lapse rates. The
latest SPC mesoanalysis showed MLCAPEs of 2000-2500 J/kg.

Current radar imagery shows an organizing line of thunderstorms
congealing just ahead of the cold front, maximized with the better
low level convergence. This activity is moving east/northeast and
is aligned fairly well with the mean flow, suggesting an increased
potential for training/backbuilding. Recent radar imagery also
shows potential for some 1.5 to near 2" hourly totals and this
aligns with the recent HREF probabilities which peak between
19-23Z for the greatest potential for reaching these intense rain
rates. Total amounts through 00Z could reach localized 3-4".

These storms will be moving across areas more susceptible to flash
flooding with low water spots and terrain and could lead to flash
flooding. 14-day rainfall departures for eastern KY and WV are
much above normal with higher than normal soil moisture
saturation. The HREF shows modest probabilities of exceeding the
12Z FFG, 20-40 percent, through the afternoon, particularly across
eastern KY into far western/southwest WV.

Taylor

ATTN...WFO...ILN...JKL...LMK...OHX...PAH...RLX...RNK...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38928055 37878041 37138296 36688463 36188772
37298756 38098454 38598263
$$
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AWUS01 KWNH 251916
FFGMPD
ILZ000-MOZ000-KSZ000-260200-

Mesoscale Precipitation Discussion 0382
NWS Weather Prediction Center College Park MD
315 PM EDT Fri Jun 25 2021

Areas affected...North-Central Missouri...East-Central Kansas

Concerning...Heavy rainfall...Flash flooding likely

Valid 251914Z - 260200Z

Summary...Flash flooding is likely across portions of
north-central Missouri and east-central Kansas with rapid
initiation of deep convection leading to rainfall rates of
2-3"+/hr. Total rainfall accumulations through 02z are expected to
reach 3-6 inches (with localized totals up to 8 inches).

Discussion...Convection is beginning to initiate this afternoon
across portions of east-central Kansas and is anticipated to
rapidly grow upscale through the evening hours. The current
mesoscale environment is characterized by SB CAPE of 3000-5000
J/kg, PWATs near 2.0 inches, and effective bulk shear of 25-45 kts
(per the latest SPC mesoscale analysis). The exception to this
analysis is across much of northern Missouri, where SB CAPE is
limited to 1000-2000 J/kg following the decay of an MCS this
morning. Efficient low-level moisture transport from the southwest
(driven by a 20-30 kt 925-850 mb jet) will quickly re-destabilize
the air mass over the next 2-4 hours (along with strong daytime
heating).

The latest CAM guidance (12z HREF suite and subsequent runs of the
HRRR) are generally in good agreement regarding convective
evolution this afternoon into the evening. The HREF guidance is
particularly concerning, painting a wide swath of 3-6 inches of
rainfall (per the probability matched mean product) through 02z. A
localized bullseye of 6-8+ inches is indicated across eastern
Kansas, as another MCS is progged to start moving in from the west
after 00z. This will likely lead to continued flash flooding
(possibly significant) overnight, and a subsequent MPD is
certainly expected to cover the evolving threat. The HRRR, on the
other hand, produces a smaller area of 3-6 inches and is slower
with the evolution of the MCS later this evening. Even in this
less bullish scenario, some flash flooding is likely through 02z
as FFG across portions of northern Missouri is quite low (less
than 1") given the tremendous amount of rainfall from the prior
MCS last night into this morning. MRMS indicates widespread 24-hr
totals of 4-10 inches, with localized totals of 10-14 inches.

Churchill

ATTN...WFO...DVN...EAX...ICT...LSX...SGF...TOP...

ATTN...RFC...ABRFC...MBRFC...NCRFC...NWC...

LAT...LON 40439336 40349159 39129098 38539131 37909271
37859445 37769544 37689775 38499780 39159639
39729554 40229456
$$
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AWUS01 KWNH 260932
FFGMPD
WIZ000-MNZ000-IAZ000-261500-

Mesoscale Precipitation Discussion 0387
NWS Weather Prediction Center College Park MD
531 AM EDT Sat Jun 26 2021

Areas affected...northeastern IA, southwestern WI and southeastern
MN

Concerning...Heavy rainfall...Flash flooding possible

Valid 260931Z - 261500Z

Summary...Slow moving showers and thunderstorms are expected to
produce locally heavy rainfall with rainfall rates of 2-3 in/hr
across portions of the Upper Mississippi Valley early this
morning. Localized rainfall totals of 3-5 inches will be possible
through 15Z.

Discussion...Regional radar imagery through 09Z showed
disorganized but slow moving showers and thunderstorms over
northeastern IA into southwestern WI. The activity was occurring
north of a stationary front that extended west-east across the
Mississippi River, out ahead of an 850-700 mb low centered over
eastern NE. While estimated instability was weak (500-1000 J/kg
via the SPC mesoanalysis), PWATs were high over the region (1.6 to
1.9 inches) supporting high rain rates. KARX rainfall estimates of
2-2.5 in/hr through 09Z over Allamakee County matched reports on
the ground, with radar-derived rates of 3+ in/hr over Crawford
County to the east. The region was located north of stronger
850-300 mb mean flow in place over MO and IL, with observed cell
motions of only 10-15 kt near the IA/MN/WI tri-state region. While
850 mb flow as also weak, repeating and training of storms has
been observed given the warm advection regime.

Warm advection and low level convergence is expected to continue
to support scattered showers/thunderstorms capable of producing
localized rainfall rates of 2-3 in/hr with slow movement of cells
contributing to isolated 3-5 inch rainfall totals through 15Z.
While much of the area has been dry over the past 1-2 weeks and
FFG is largely 3+ inches in 3 hours for much of the area,
efficient rainfall production may support some localized flash
flooding across portions of northeastern IA, southwestern WI and
southeastern MN this morning.

Otto

ATTN...WFO...ARX...DMX...MKX...

ATTN...RFC...NCRFC...NWC...

LAT...LON 44249048 43948956 43568938 43058946 42859089
42799199 42959245 43409260 44039186
$$
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AWUS01 KWNH 261229
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-261700-

Mesoscale Precipitation Discussion 0388
NWS Weather Prediction Center College Park MD
828 AM EDT Sat Jun 26 2021

Areas affected...Southwest MO... Ext Northeast OK, Southaest KS &
Northwest AR...

Concerning...Heavy rainfall...Flash flooding possible

Valid 261230Z - 261700Z

SUMMARY...Ongoing early morning flash flood threat, slowly
diminishing...

DISCUSSION...Regional RADAR mosaic depicts NE to SW line of
thunderstorms across SW MO continuing to remain aligned parallel
to the deep layered steering flow within a broad large scale trof.
Typical of early morning convection at diurnal minimum in
instability, thunderstorms are taking on a more tendril appearance
with weak isentropic ascent across the remaining outflow boundary
with a stronger cell at the intersection of an MCV/weak shortwave
acting as a caboose to the train of thunderstorms with a solid
cold pool to aid in such acceleration.

While instability is waning overall, there is a remaining small
untapped pool along the leading edge across south-central MO at
the intersection of the preceding outflow boundary. As such
recent uptick was noted with overshooting tops/cooling tops on
GOES-E 10.3um. Nearly 100% saturated lowest levels and total
PWats over 2" and with solid 25-30kts of confluent
inflow/entrainment per SGF VWP support continued intense rainfalls
with rates over 2-2.5"/hr possible. Combine this with upstream
weaker but still efficient thunderstorms suggest training and
longer duration to support 2-4" of additional rain maintaining a
possible flash flooding threat over the next few hours.

Gallina

ATTN...WFO...SGF...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC...

LAT...LON 38149250 37759191 37039261 36419392 36229461
36399507 37109472 37789390
$$
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AWUS01 KWNH 282100
FFGMPD
MDZ000-VAZ000-WVZ000-290100-

Mesoscale Precipitation Discussion 0405
NWS Weather Prediction Center College Park MD
459 PM EDT Mon Jun 28 2021

Areas affected...West Virginia...Ext Western MD...

Concerning...Heavy rainfall...Flash flooding possible

Valid 282100Z - 290100Z

SUMMARY...Numerous pulse thunderstorms with rain rates and
sub-hourly totals of 1.5-2.5" pose possible isolated flash
flooding conditions.

DISCUSSION...Deeper moisture/instability across the Cumberland
Plateau is sloshed up into the higher terrain of the central WV
Appalachians with weak upslope and southwesterly flow pushing the
tight gradient in moisture into the area of concern. Deeper mean
layer flow is highly confluent across the 850-7H layer on the
western periphery of a sharp anticyclonic flow. Upslope flow from
the east as well, provided sufficient surface moisture convergence
to initiate a line of pulse to weakly organized convection. LPW
aslo denotes the main updraft core from 850-5H is about 1.1"
indicative of high moisture. Given modest flux convergence may
result in rates of 2-2.25"/hr. Given complex terrain, these
hourly totals have the potential to exceed 1 hour FFG values
particularly across central to northeast WV where the values are
less than 2". Outflow is likely to kick off additional cells
perhaps even cells eastward...and with mean deep layer flow
generally north-northwest to north-northeast, there may be some
repeat tracks that would further increase the potential to even
exceed 3hr FFG values which are generally below 2.5". Currently
threat is from Webster toward Randolph county but should expand
both northeast and southwest with time along with the overall
general propagation of the current cells toward the
north-northwest through the remainder of daylight hours before
remaining instability wanes.

Gallina

ATTN...WFO...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 39667953 39577886 39147877 38617937 38048067
37478179 37958233 38918137 39548051
$$
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AWUS01 KWNH 282316
FFGMPD
ILZ000-MOZ000-290500-

Mesoscale Precipitation Discussion 0408
NWS Weather Prediction Center College Park MD
716 PM EDT Mon Jun 28 2021

Areas affected...Southwest to Central IL...

Concerning...Heavy rainfall...Flash flooding possible

Valid 282315Z - 290500Z

SUMMARY...Cycles of highly efficient but generally short-lived
thunderstorms traversing saturated ground conditions pose highly
scattered but likely flash flooding through early overnight hours.

DISCUSSION...Moisture streaming out of the western Gulf along the
western perimeter of deep sub-tropical high across the South surge
into proximity of the deep layer positive-tilt trof that has
dominated the Central U.S. for days. Ample deep moisture remains
pooled just southeast of the mean trof axis along/southeast of a
surface stationary front with near/over 2" total PWats extending
from southern Lake Michigan to southeast KS. While overall
thermal profiles continue to warm with lessening lapse rates day
by day, peak solar angle is sufficient to heat the surface
conditions to support SBCAPEs of 3000 J/kg within the warm sector.
Weak but sufficient 15-20kts of LLJ advect the unstable air into
proximity of weak mid to upper level impulses to support scattered
convective development across the same general axis.

Once again, an active cycle is blossoming across Central MO with
numerous cells breaking out with tops cooling below -60C.
However, winds are weak and each cell may only cycle with one or
two overshooting updrafts before weakening and becoming more
stratiform in nature. So peak rates of 2.5"/hr are common and may
be in close proximity to other cells, given deep layered
unidirectional steering flow, there are some occasional repeats
within a 2-3 hour period to support isolated 3-4" totals. The
real concern here is the axis of development remains stationary
over days so ground conditions are fully saturated with NASA SPoRT
LIS 0-40cm ratios generally over 90% from SE KS to NW IND...with
pockets of near 100% very common through that axis. As a result
FFG values are likely to be exceeded (less than 1.5"/hr and
2"/3hr) across much of MO into SW IL. There is greater distance
between instability and moisture axis across NE IL into IND, and
so many hi-res CAMs led by recent HRRRs suggest development to
remain in proximity to MO and SW IL through the evening and
overnight hours. ARW solutions have been poorer and FV3-LAM has
been worst performing through the afternoon to help in trying to
pinpoint any specific area/county within the area of concern.

Gallina

ATTN...WFO...DVN...EAX...ILX...LSX...SGF...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 40759026 40678900 39818865 39148941 38379055
37339246 37049333 37019418 37359456 38509435
39439316
$$
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AWUS01 KWNH 282153
FFGMPD
TXZ000-OKZ000-290300-

Mesoscale Precipitation Discussion 0406
NWS Weather Prediction Center College Park MD
553 PM EDT Mon Jun 28 2021

Areas affected...North-central to Southwest OK...Northwest to
West-Central TX...

Concerning...Heavy rainfall...Flash flooding likely

Valid 282155Z - 290300Z

SUMMARY...Scattered highly efficient thunderstorms moving across saturated/flooded ground pose continued scattered flash flooding
concerns through early overnight hours.

DISCUSSION...Large scale positive tilt trough continues to be
locked in across the Southern Plains to Upper Mississippi Valley
with continued pumping of warm, moist and unstable air off the
Western Gulf. This low level air is generally divergent upstream
across south-central OK into Northeast TX, with ample time to heat
further with continued solar insolation, but not enough forcing to
ascend. An axis of 2000-2500 J/kg of MLCAPE exists from Reagan
county, TX to Osage county OK with moisture pooling along the
confluent side of the return flow across OK reaching over 2" while
lower across West Central TX, it remains over 1.75".

However, once it approaches the mid-level trof and stationary
surface boundary, moisture convergence is sufficient to result in
bands of scattered convection. Eventually, the steering flow
reaches a col across Northwest Texas slowing overall translation
of the cells resulting in longer local residency time. However,
given instability/moisture axis is now a few tens of miles further
east than the prior round, cell motions are probable to be
slightly quicker with less stationary nature as seen in the late
morning/early afternoon hours.

However, the area of activity/redevelopment will occur across
areas that have remained well above normal and are fully saturated
according to NASA SPoRT LIS 0-40cm soil saturation ratios. As a
result flash flooding is considered likely given rates of
2-2.5"/hr and FFG values less than 2.5"/3hrs across much of the
discussion area. Though flash flooding is not likely across the
entire area as the organized forcing areas are much more
scattered/clustered, isolated 3-4" totals are possible and given
placement to recent rainfall or urban centers could produce
considerable flash flooding conditions.

Gallina

ATTN...WFO...AMA...FWD...LUB...MAF...OUN...SJT...TSA...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON 36939731 36919581 35989569 34279727 33529832
32399954 31760017 31240111 31310182 32140205
33960081 35099982 36099869
$$
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AWUS01 KWNH 301750
FFGMPD
PAZ000-WVZ000-OHZ000-302249-

Mesoscale Precipitation Discussion 0418
NWS Weather Prediction Center College Park MD
149 PM EDT Wed Jun 30 2021

Areas affected...Southeast OH and Southwest PA

Concerning...Heavy rainfall...Flash flooding possible

Valid 301749Z - 302249Z

SUMMARY...Recent radar and satellite trends indicate the potential
for isolated flash flooding across portions of southeast OH, far
northern WV and southwestern PA through mid afternoon.

DISCUSSION...Latest surface observations and visible satellite are
detecting a southwest to northeast oriented convergence axis from
southeast OH into southwest PA. Convection has rapidly developed
along this axis over the past hour or two. Meanwhile we have also
been tracking an intense small convective cluster as it tracks
across southeast OH. The motion of this convective cluster should
take it along the aforementioned convergence axis....resulting in
a narrow axis of potential training over the next few hours.

The environment is characterized by MLCAPE over 2000 J/kg and PWs
around 1.75"...plenty sufficient for heavy rainfall rates. Latest
MRMS data indicates instantaneous rainfall rates of around 4" in
the heavier activity. Thus it would only take relatively brief
training to get rainfall amounts approaching 2" in under an hour.

Soil conditions over most of the MPD area are at well below normal
saturation levels. So this region is not in an overly susceptible
position for flash flooding. It will likely take some training to
result in any flooding...and even at that it will most likely stay
confined to any more susceptible low lying or urban areas.
Nonetheless the latest radar/satellite representation does suggest
a small scale training risk over this area over the next couple
hours resulting in the aforementioned localized flash flood risk.

Chenard

ATTN...WFO...CTP...PBZ...RLX...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 41107881 40877845 40507878 40017973 39678050
39548139 40148167 40388150 40728060 40957974
$$
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AWUS01 KWNH 251154
FFGMPD
AZZ000-251730-

Mesoscale Precipitation Discussion 0634
NWS Weather Prediction Center College Park MD
753 AM EDT Sun Jul 25 2021

Areas affected...South-Central Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 251151Z - 251730Z

Summary...Isolated instances of flash flooding are possible
through mid-morning with sub-hourly rainfall rates as high as 1-2
inches over already highly saturated soils.

Discussion...Overall convective activity continues to wind down
across Arizona, but a lingering mid- and upper-low looks to
continue to support isolated instances of flash flooding with
pulse showers and thunderstorms capable of very high sub-hourly
rainfall rates. Vorticity maxima rotating around the parent low
will support sporadic convective initiation, but the updrafts look
to remain quite small spatially with a distinct lack of larger
scale forcing for uplift. Despite this, diffluence aloft will
allow these small showers and thunderstorms to occasionally
achieve deep convective status as GOES IR indicates cloud tops
cooling to -50deg C locally. Southwestern Arizona has the best
chance of realizing these fleeting strong updrafts over the next
several hours, as instability and precipitable water values align
at their highest values over this region (SB CAPE of near 1500
J/kg and PWATs of near 2.0 inches respectively).

The latest hi-res CAMs are in solid agreement through 18z with
isolated convection capable of very high sub-hourly rainfall
rates. HREF 40-km neighborhood probabilities of 1-h QPF exceedance
of 2 inches are near 30% across portions of southwest Arizona
through about 16z, and HRRR hourly max 15 min accumulations
approach 2" (indicating an instantaneous hourly rate of about
6"/hr). While these tremendous rainfall rates are not expected to
persist over any particular location for a long length of time, it
does illustrate how quickly 1-2" of rainfall could occur. This is
indeed the biggest driver of the flash flood threat, as any one
location is not anticipated to exceed 2-3" of rainfall.

The threat for isolated flash flooding would be high enough
already given the overall favorable atmospheric environment for
heavy rainfall, but the additional consideration of antecedent
conditions certainly elevate the threat. NASA SPoRT-LIS soil
moisture anomalies remain at extreme levels, exceeding the 98th
percentile across the majority of the highlighted region
throughout the 0-200 cm depth. These data indicate that any
sub-hourly rates of 1-2" will quickly runoff and present a flash
flood threat locally, especially for (normally) dry washes, burn
scars, and metropolitan areas.

Churchill

ATTN...WFO...FGZ...PSR...TWC...VEF...

ATTN...RFC...CBRFC...NWC...

LAT...LON 34771276 34591143 33801057 32751034 32041033
31431066 31531171 31841271 32081350 32351439
33001434 33661424 34391360
$$
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AWUS01 KWNH 251749
FFGMPD
AZZ000-UTZ000-NVZ000-CAZ000-260000-

Mesoscale Precipitation Discussion 0635
NWS Weather Prediction Center College Park MD
148 PM EDT Sun Jul 25 2021

Areas affected...Much of Arizona...Southwestern Utah...Far
Southeastern Nevada

Concerning...Heavy rainfall...Flash flooding possible

Valid 251747Z - 260000Z

Summary...Widely scattered instances of flash flooding are likely
to continue across south-central portions of Arizona, expanding
northward into the higher terrain and neighboring portions of
southwestern Utah and far southeastern Nevada. Sub-hourly rainfall
rates of 1-2" will drive the flash flood threat. Localized
accumulations may also approach 2-4 inches.

Discussion...Recent trends via KIWA (Phoenix) radar indicate an
expanding flash flood threat late this morning within an area of
deep moisture convergence, driven by a decaying upper-level low
(gradually becoming more of an open inverted trough axis). The
mesoscale environment is characterized by precipitable water
standard deviations of +3 (near or exceeding 2.0 inches) and SB
CAPE of 1000-2000 J/kg. The best moisture and instability axis
currently aligns over southeastern Arizona, but is anticipated to
expand northward into the higher terrain of north-central Arizona
and into neighboring portions of southwestern Utah and far
southeastern Nevada amid daytime heating. Convective activity has
been capable of sub-hourly rainfall rates of 1-2" and has quickly
led to rapid runoff over already highly saturated soils. Washes
that are normally dry may quickly fill with fast moving water due
to these rapid rainfall accumulations, though the spatial extent
of the heaviest downpours is expected to remain fairly limited.

The latest hi-res CAM guidance (12z HREF suite and more recent
HRRR runs) support the northward expansion of the flash flood
threat this afternoon as mostly clear skies to the north are
allowing for significant destabilization amid peak daytime
heating. SB CAPE values are forecast to reach as high as 2000-4000
J/kg between Flagstaff and Las Vegas, fueling new vigorous
convective initiation. The aforementioned models support localized accumulations of 2-4 inches, while 3-hr FFG is mainly near 2
inches. Many locations have already received plentiful rainfall
throughout the past week as well, so FFG in general may also be a
bit overdone. Washes, burn scars, and metropolitan areas should
pay close attention to the evolving flash flood threat through the
afternoon hours.

Churchill

ATTN...WFO...FGZ...PSR...SLC...TWC...VEF...

ATTN...RFC...CBRFC...NWC...

LAT...LON 38461179 38291109 37731105 37401147 37221236
36691303 36121296 35861266 35711218 35601091
35380981 34370936 33240987 32721039 32271025
31630996 31301030 31271065 31321111 31461153
31711238 32011346 32371447 32691445 33071443
33391441 33761423 34181419 34361422 34901443
35441472 36081467 36751425 37251409 37761381
38211321 38421258
$$
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AWUS01 KWNH 300021
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-300615-

Mesoscale Precipitation Discussion 0891
NWS Weather Prediction Center College Park MD
821 PM EDT Sun Aug 29 2021

Areas affected...southeastern LA, southern MS into southwestern AL

Concerning...Heavy rainfall...Flash flooding likely

Valid 300017Z - 300615Z

Summary...Significant heavy rainfall and flash flooding associated
with Hurricane Ida will continue to impact southeastern LA into
southern MS over the next 6 hours. An additional 4-8 inches is
expected to the right of Ida's forecast track, some of which will
fall on top of a broad 4-8 inches which has already fallen.

Discussion...GOES East infrared satellite imagery has shown
warming within the central dense overcast (CDO) surrounding
Hurricane Ida's eye over the past 2-3 hours but Ida remains a
major hurricane with well defined banding of heavy rain in the
northern and eastern eyewall. Observed rainfall rates over
southeastern LA have generally been 1-2 in/hr through early
evening, but rates over 2 in/hr have occasionally been observed as
well. At 00Z, Ida was located roughly 25 miles WSW of New Orleans
and tracking toward the northwest near 9 kt according to the 00Z
NHC update. This motion will continue to focus the heaviest
rainfall rates to the immediate north and east of Ida's eye as the
hurricane tracks toward southwestern MS tonight.

VAD wind data from KLIX appears to be located within the core of
strongest 850 mb winds near 80 kt, located about 60 miles of the
center of Ida, supporting extreme moisture transport toward the
north. To the south of Ida, recent radar imagery showed spiral
rain bands south of the MS River Delta, feeding cyclonically
toward the northeast and north into far southeastern LA along with
a separate banded feature into southern MS. These banded
structures are likely to continue over the next several hours,
with the greatest persistence forecast over southeastern LA, from
the marshes of the MS River Delta to north of Lake Pontchartrain
and into portions of adjacent southern MS...where an additional
4-8 inches of rain is expected through 06Z. Farther to the east,
training of outer rain bands within about 100 miles of the MS and
AL Gulf Coast will likely result in rainfall rates varying between
1-3 in/hr and areas of flash flooding. Additional 6-hour rainfall
from these training bands away from the center of Ida are expected
to produce an additional 2-4 inches of rain through 06Z.

Otto

ATTN...WFO...JAN...LCH...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 32138957 32018858 31618786 31158745 30748716
30158709 29978795 29698853 28938890 28688971
28889055 29619131 30319168 31279156 31919050

$$
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AWUS01 KWNH 301209
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-301800-

Mesoscale Precipitation Discussion 0893
NWS Weather Prediction Center College Park MD
809 AM EDT Mon Aug 30 2021

Areas affected...Far Southeastern Louisiana...Much of
Mississippi...Southern Alabama

Concerning...Heavy rainfall...Flash flooding likely

Valid 301206Z - 301800Z

Summary...Flash flooding is likely to continue in association with
Tropical Storm Ida. Some flash flooding may be significant with an
additional 4-8" of rain falling across areas already highly
saturated from previous 24-36 hour totals.

Discussion...Tropical Storm Ida is moving somewhat slowly (8 mph)
northward over southwestern Mississippi, per the latest (7AM CDT)
NHC advisory. Ida has become a rather lopsided system, with most
of the heavy rain (and other impacts) now concentrated on the
eastern half of the circulation. A tremendous amount of rainfall
has fallen over the past 24 hours, mainly across southeastern
Louisiana and southern Mississippi/Alabama. A large footprint of
6-18" is evident across southeast LA and a portion of coastal MS,
while 2-6" totals are quite common elsewhere in the highlighted
region. NASA SPoRT-LIS 0-40 cm soil moisture anomalies were above
the 98th percentile for the vast majority of the 6+" accumulation
region (unsurprisingly). This indicates particular sensitivity to
additional rainfall, and unfortunately that looks to be where much
of the forecast amounts are setting up for this morning.

The mesoscale environment associated with the eastern half of TS
Ida includes highly anomalous PWATs of 2.2-2.8 inches, MUCAPE up
to 3000 J/kg (right along the Gulf coast), and very impressive
low-level moisture transport and deep moisture flux convergence.
The highest magnitudes of these parameters mostly overlap along
the Gulf coast, from far southeastern LA north-northeastward into
southern Mississippi and Alabama. This is where the highest
neighborhood probabilities (via the 06z HREF) of 5" exceedance
exist, and additional localized totals of 4-8" may occur here.
Rainfall rates will likely average 1-2"/hr with most banding, but
occasionally rates may reach up to 2-4"/hr given the highly
favorable environment for heavy rainfall and potential for
training. Recent HRRR runs (05-10z) have been very consistent with
the placement and amounts of QPF, providing a relatively high
confidence forecast for flash flooding (some significant) through
18z.

Churchill

ATTN...WFO...BMX...JAN...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 33528979 33208838 32808751 31878686 31038654
30338668 30148697 30018814 29358872 28798920
28809033 29069098 29469038 29759007 30048977
30568975 30928986 30939028 31289045 31779089
32189102 32749094 33279055

$$
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AWUS01 KWNH 311510
FFGMPD
PAZ000-WVZ000-OHZ000-312109-

Mesoscale Precipitation Discussion 0906
NWS Weather Prediction Center College Park MD
1110 AM EDT Tue Aug 31 2021

Areas affected...Ohio Valley

Concerning...Heavy rainfall...Flash flooding possible

Valid 311509Z - 312109Z

Summary...Slower moving thunderstorms developing this morning
across the Ohio Valley will be capable of producing localized
heavy rainfall with rain rates up to 2"/hr at times. This may lead
to isolated instances of flash flooding.

Discussion...Moisture streaming northward associated with T.D. Ida
and an approaching shortwave trough from the Plains will work
together along an existing frontal boundary to produce isolated to
scattered thunderstorms into the afternoon hours. This activity is
already beginning to develop along the better moisture gradient
(1.6-1.8") and also along the bubble of higher instability already
present (SBCAPE of 1500 J/kg).

The last several runs of the HRRR and new 12Z hi-res guidance is
showing a narrow west/east band of slower moving thunderstorms
into the afternoon hours that should setup across portions of
east-central IN, central OH, and western/southwest PA. The
favorable environment (tall/skinny CAPE profiles and warm cloud
depths up to 4 km will help drive more efficient rain rates,
especially into the afternoon hours.

The HREF probabilities support hourly totals between 1-2" at times
with a good signal for exceeding 6-hr FFG and 5-year ARI,
particularly across central OH into western/southwest PA, through
21Z. While most areas will likely see totals through 21Z of 1-2",
some isolated higher end amounts of 2-4" appear possible.

Taylor

ATTN...WFO...CLE...CTP...ILN...PBZ...RLX...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40938067 40487810 39877861 39798142 39598446
40248429
$$
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AWUS01 KWNH 311747
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-312346-

Mesoscale Precipitation Discussion 0907
NWS Weather Prediction Center College Park MD
147 PM EDT Tue Aug 31 2021

Areas affected...Southern Appalachians

Concerning...Heavy rainfall...Flash flooding possible

Valid 311746Z - 312346Z

Summary...Rain bands associated with Tropical Depression Ida will
bring heavy rainfall to portions of the southern Appalachians this
afternoon. Rain rates of 1-2"/hr over saturated soils could lead
to flash flooding.

Discussion...The center of T.D. Ida, now over northern Alabama,
will continue moving east/northeast, drawing up anomalously high
moisture across the southern Appalachians. Recent blended TPW
products show values exceeding 2" with local maxima 2.4-2.5"
across northern Alabama. Visible satellite imagery shows a few
breaks in the convective bands and this has allowed upwards of
1500 J/kg of SBCAPE to develop across northern Georgia and far
northeast Alabama.

Over the next several hours, a few convective bands will lift
northeast across upstate SC and western NC providing good upslope
component for training bands and enhanced rainfall. As the storm's
center approaches during peak heating and with the clearing wedge
seen in visible satellite, this is likely to fill in and track
additional storms over northern GA and southwest NC. Storm motions
becoming aligned parallel to the mean flow and favorable tropical
environment for enhanced rain rates (tall/skinny CAPE and WCDs
near 4.3 km) should result in highly efficient low topped
convective bands.

There is a strong signal in the 12Z HREF for rainfall totals
through 00Z to exceed the local 5-10 year ARI with high
probabilities of 1-2"/hr rain rates. Total amounts of 2-3" with
some localized 3-4" totals will be possible.

Much of the outlook area has been wetter than normal the last 7-14
days and the NASA SPoRT soil moisture for the 0-100 cm layer is
running 90+ percent. As a result, the expected rain rates and
totals are likely to exceed the FFGs and lead to instances of
flash flooding, especially for the more sensitive terrain areas of
southwest to western NC.

Taylor

ATTN...WFO...FFC...GSP...MRX...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 35958219 35118201 34508336 34288438 34618504
35028460 35588322

$$
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AWUS01 KWNH 171601
FFGMPD
TNZ000-MSZ000-LAZ000-MOZ000-ARZ000-172200-

Mesoscale Precipitation Discussion 0978
NWS Weather Prediction Center College Park MD
1200 PM EDT Fri Sep 17 2021

Areas affected...Northern Louisiana, Eastern Arkansas, far
Southwest Tennessee

Concerning...Heavy rainfall...Flash flooding possible

Valid 171600Z - 172200Z

Summary...Showers and thunderstorms will increase through the
afternoon across Louisiana and Arkansas. Rain rates within this
convection may exceed 2"/hr at times, producing 1-3" of rainfall
with locally higher amounts to 5". Flash flooding is possible.

Discussion...GOES-E IR imagery this morning indicates cloud tops
cooling across Louisiana and Arkansas east and north of the center
of Post Tropical Cyclone Nicholas. These cooling cloud tops are
indicative of strengthening convection, which is also evident as
an expansion of reflectivity on the regional radar mosaic and
echoed by an increase in the 15-min lightning density. Recently, a
nearly stationary thunderstorm produced estimated rain rates in
excess of 3"/hr northwest of Shreveport, LA, in response to an
axis of deformation aligned within a ribbon of elevated
instability surging northward from the Gulf of Mexico.

As Post T.C. Nicholas continues to drift slowly northward, its
circulation will increasingly interact with a mid-level trough of
low pressure digging southeast out of Texas. This will intensify
the deformation axis from northern LA into far southwest TN, which
is reflected in recent RAP progs. At the same time, increasing
low-level southerly flow out of the Gulf of Mexico will draw
enhanced PWs of more than 2" measured by the GPS observations, and
MLCape of 1000-1500 J/kg analyzed by the RAP/SPC Mesoanalysis,
northward and into the region. This low-level advection will then
impinge into the axis of deformation to drive locally intense
ascent which should fuel a rapid expansion of convection through
the aftn. This is suggested by many of the available high-res
CAMs, and via HREF probabilities indicating a narrow corridor of
high probabilities for 2"/hr rain rates and greater than 60%
chance for 3"/6hrs. Mean 0-6km wind during this time will be
generally E/SE at 5 kts or less, with propagation vectors becoming
increasingly opposed to the mean wind leading to the potential for
backbuilding and slow moving thunderstorms, within which rain
rates to 2"/hr could produce 1-3" of rainfall with isolated
amounts to 5".

Although rain has been limited the past 14-days noted by AHPS
rainfall that is just 5-25% of normal, 200cm soil moisture is
still above the 90th percentile across parts of northern LA and
southern AR. This indicates that while some absorption of rainfall
into the soils is likely, intense rain rates could still lead to
runoff and flash flooding, and the HREF exceedance probabilities
reach 20-30% despite FFG that is generally 2.5-4"/3hrs. Flash
flooding will be possible through peak heating, and is most likely
where any backbuilding can lengthen the duration of these
excessive rain rates.


Weiss

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 36038984 36038922 35988893 35208906 34728947
33939013 33299067 32859101 32309160 31949217
31899283 32069363 32329402 32919396 33839291
34889200 35479149 35819079
$$
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AWUS01 KWNH 171830
FFGMPD
FLZ000-GAZ000-ALZ000-MSZ000-LAZ000-172300-

Mesoscale Precipitation Discussion 0979
NWS Weather Prediction Center College Park MD
229 PM EDT Fri Sep 17 2021

Areas affected...Southeastern LA...Southern MS/AL...FL
Panhandle...Far Southwest GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 171828Z - 172300Z

Summary...Scattered convection will occasionally produce rainfall
rates up to 2-3"/hr across portions of the Gulf coast this
afternoon. Given the saturated soils across the area, flash
flooding remains a possibility.

Discussion...Post-tropical Cyclone Nicholas continues to cling to
life, drifting northward over Louisiana. Much of the flash flood
threat this afternoon will continue to be focused to the east and
southeast of the circulation, where low-level flow from the Gulf
of Mexico encounters portions of the Gulf coast. The mesoscale
environment across the region is characterized by PWATs of
1.8-2.2 inches (with as much as 1.1" concentrated below 850 mb),
SB CAPE of 2500-4000 J/kg, and modest effective bulk shear of
15-20 kts. The northward movement of Nicholas (as well as the
ridge axis over the Gulf) has helped to increase low-level flow
(along with the mesoscale influence of the sea breeze), but
moisture transport remains fairly muted despite this. This is
likely because there is already plenty of low-level moisture in
place, but the ragged, weakening circulation of Nicholas is
struggling to significantly organize convective activity/banding.
That said, rainfall rates are occasionally reaching 2-3"/hr given
the overall favorable mesoscale environment for heavy rainfall.

The primary concern for flash flood potential continues to be the
already saturated soils across the region, as NASA SPoRT-LIS 0-40
cm soil moisture anomalies top the 98th percentile for the bulk of
the area. This speaks to the tremendous amount of rainfall that
has fallen as of late, with MRMS 72-hr totals depicting a fairly
large area of 4-8+ inches along coastal MS/AL and surrounding
portions of LA/FL. Localized spots have also seen 2-3" over the
past 6 hours per MRMS, so antecedent conditions are certainly
concerning. All that said, the disorganized nature of the
convection should limit coverage of flash flooding with a distinct
decrease in coverage and intensity anticipated after 23z per the
latest guidance and typical diurnal trends.

Churchill

ATTN...WFO...BMX...JAN...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 32548637 31628527 30918425 30538336 30108332
29658354 29778405 29498510 29928595 30168675
30168777 30048849 29648880 29138886 28908924
29029001 29019096 29289120 29729100 30709132
31149130 31799090 32319018 32228945 32168849
$$
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AWUS01 KWNH 241515
FFGMPD
NVZ000-CAZ000-250010-

Mesoscale Precipitation Discussion 1098
NWS Weather Prediction Center College Park MD
1111 AM EDT Sun Oct 24 2021

Areas affected...Northern CA

Concerning...Heavy rainfall...Flash flooding likely

Valid 241510Z - 250010Z

SUMMARY...Strong atmospheric river conditions continue to blast
northern CA with heavy rain and locally significant concerns for
flash flooding and debris flows around the area burn scars.

DISCUSSION...The latest GOES-17 GeoColor RGB satellite imagery
shows a very deep area of low pressure offshore of the Pacific
Northwest driving a strong atmospheric river into northern CA as a
powerful 130 to 150+ kt upper-level jet roars through the southern
flank of the associated upper trough.

A cold front has already begun to edge across the coastal ranges
of northern CA and there continues to be a 50 to 60+ kt low-level
jet along and just ahead of this which is facilitating very strong
moisture transport parameters into the coastal ranges and the
interior foothills and high terrain of the northern Sierra-Nevada.
In fact, the IVT values for the core of this atmospheric river
event are nearing peak and should max out in between 1250 and 1500
(kg per m/s) based on the 06Z NAM/GFS solutions.

Already there have been impressive hourly rainfall rates
associated with the event, with some of the coastal ranges north
of San Francisco seeing hourly QPEs in the 0.5" to 0.8+" range,
and the foothills of the northern Sierra-Nevada seeing values of
as much as 0.4" to 0.6+". This has already led to concerns for
enhanced runoff around some area burn scars with notable debris
flow potential around the fresher burn areas from the 2021 fire
season in particular.

Going through the remainder of the morning and into the afternoon
time frame, the strong orthogonal deep layer fetch of Pacific
moisture relative to the terrain will continue to foster enhanced
orographic rainfall with the overall axis of heavy rainfall
gradually settling south with time as the main cold front and a
secondary boundary advance inland and down to the southeast. Very
strong warm-air advection and related isentropic ascent coupled
with the anomalous PW axis (1.25 to 1.5 inches) which will be
running locally over 3 standard deviations above normal will also
be generating heavy rainfall across the Sacramento Valley as well.
Even areas of the Sacramento Valley will be looking at potentially
seeing hourly rainfall amounts approaching or locally exceeding a
0.50". However, overall the highest rates will likely still be
confined to the coastal ranges north of the San Francisco Bay area
and into the northern Sierra-Nevada (mainly north of Lake Tahoe)
where some rates may still approach or briefly exceed 0.75"/hour.

The latest HREF guidance suggests additional storm totals amounts
for the coastal ranges and the foothills/high terrain of the
northern Sierra-Nevada reaching 3 to 5+ inches going through 00Z
(5PM PDT). This rainfall will likely drive locally significant
concerns for flash flooding and debris flows around the area burn
scars.

Orrison

ATTN...WFO...EKA...HNX...MFR...MTR...REV...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON 41852098 41532031 40902003 40222013 39322000
38411948 37671894 37421967 38012058 37892142
37052148 36982175 37012221 37902256 38262320
39162382 39762396 40122425 40482441 40882407
41352365 41472314 41432225
$$
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AWUS01 KWNH 242146
FFGMPD
INZ000-ILZ000-MOZ000-IAZ000-250343-

Mesoscale Precipitation Discussion 1099
NWS Weather Prediction Center College Park MD
545 PM EDT Sun Oct 24 2021

Areas affected...central Missouri, southern Iowa, Illinois, and
northern Indiana

Concerning...Heavy rainfall...Flash flooding likely

Valid 242143Z - 250343Z

Summary...Areas of flash flooding will increase in likelihood
through the evening especially in areas that received copious
rainfall this morning and where training/repeat convection can
materialize.

Discussion...Scattered thunderstorms are intensifying along an
axis that generally extends from near COU to north of PIA. The
storms have gradually intensified in response to both approaching
ascent from a mid-level wave centered over southeastern Nebraska
and instability across a broad warm sector in much of the
discussion area south of a warm front. The storms within the axis
were lifting northeastward across the warm front while also
producing localized areas of 1-1.5 inch/hr rainfall rates. These
rates were nearing FFG thresholds in a few areas - especially
where morning rainfall has resulted in wet soils and <1.5 inch/hr
FFGs. A few spots have exhibited FFG thresholds as low as 0.5
in/hr in spots. Localized training of storms will allow for a
flash-flood risk in the short term.

Over time, the eastward advancement of the mid-level wave in
Nebraska will allow for more lift to overspread the warm sector
and potentially allow for expanded coverage of heavier
precipitation especially from Missouri northeastward. Some of
this expansion of coverage was already underway in south-central
Missouri. Additionally, increasing flow in the 1-2 km AGL layer
(attendant with a 60-65 kt low-level jet) will remain
perpendicular to the slow-moving warm front and allow for another
potential focus of convection especially from northern Illinois
into northeastern Indiana. Through 04Z or so, a few areas could
experience 2-3 inches of rainfall as multiple rounds of convection
traverses the area (including storms along the cold front now in
western Missouri). Localized areas may exceed 4 inches beneath
training convection - most likely in Illinois. These rainfall
totals will likely cause areas of flash flooding to occur.

Farther northwest, an area of convection tied to the mid/upper low
persists in southwestern Iowa, while a couple of supercells are
migrating east-northeastward along the cold front in northwestern
Missouri. These areas of convection area a bit more progressive
in nature and should result in only a localized/spotty flash flood
risk.

Cook

ATTN...WFO...DMX...DVN...EAX...ILX...IND...IWX...LOT...LSX...
SGF...

ATTN...RFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON 41919258 41709138 41588973 41578837 41428700
41248672 40858621 40278626 39808682 39478793
38918983 38119167 37639275 38269294 39029269
39699306 40529366 41219398 41739355
$$
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AWUS01 KWNH 162019
FFGMPD
TNZ000-MSZ000-LAZ000-ARZ000-TXZ000-170217-

Mesoscale Precipitation Discussion 1151
NWS Weather Prediction Center College Park MD
318 PM EST Thu Dec 16 2021

Areas affected...portions of the Mid-South

Concerning...Heavy rainfall...Flash flooding possible

Valid 162017Z - 170217Z

Summary...Showers and thunderstorms are beginning to show an
uptick in coverage near the ArkLaTex. Hourly totals to 2" and
local amounts to 4" are possible over the next several hours.

Discussion...Water vapor imagery shows a shortwave moving through
northeast AR and eastern OK at the present time. Veggie Band
images show the low cloud deck across southern AR is eroding, with
new development within an ML CAPE pool of 1000-2000 J/kg.
Effective bulk shear is 35-40 knots, which with the unidirectional
flow with height is trying to develop a linear convective band.
Earlier this morning, a short-lived mesocyclone was noted which
amped up hourly rain totals to 2".

While the model guidance is not in unanimous agreement, there is a
good signal for local 2-3" amounts between Memphis, northwest MS,
and southern AR over the next several hours amongst the 12z NAM
CONEST, 12z ECMWF, 12z Canadian Regional, and 12z ARW guidance
while HRRR runs show an increased trend in amounts over the past
several hours. This is an area where the highest precipitable
water values and the stronger 850 hPa inflow is expected to
persist today. The GFS-based GDI hints at growing convective
coverage through at least 00z, which should act to cause a greater
frequency of hourly totals to 2" this afternoon. A front moving
into the area is expected to slow down, which also should act to
amp the rainfall potential -- believe local amounts to 4" are
possible. Since precipitation in this area has been roughly 25-50
percent of average over the past couple weeks, impacts are
expected to be mainly across urban areas.

Roth

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 35428888 34408935 33459117 32849410 33189484
33369475 33689438 34219392 34609294 35049197
35419027
$$
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AWUS01 KWNH 181451
FFGMPD
TXZ000-182030-

Mesoscale Precipitation Discussion 1158
NWS Weather Prediction Center College Park MD
950 AM EST Sat Dec 18 2021

Areas affected...Southeast Texas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 181450Z - 182030Z

SUMMARY...Slow southeastward drift of frontal convection; new
development downstream posing potential mergers/training resulting
in possible flash flooding.

DISCUSSION...RADAR and GOES-E 10.3um loop depict solid line of
strong thunderstorms from Hays/Guadalupe county in central Texas
toward northeast Texas in vicinity of Rusk/Gregg county along the
leading edge of the slowly southeast drifting cold front. Further
north along the line, the mean flow is less parallel to the cell
motions, so residency is likely a limiting factor for the
potential for flash flooding; however, ample moisture flux
convergence and surface based instability to 500 J/kg support some
higher instantaneous rates of up to 1.75 that could pose
driving/urban short-term concerns. With upstream redevelopment,
the higher theta-e air may be obstructed and reduce efficiency
further as the cells move into northeast/west-central LA.

Further south, forward propagation is toward the southeast feeding
into the warmer much more unstable air mass across Southeast Texas
where SBCAPEs are starting to reach values of 1500-2000 J/kg.
Rates of 2"/hr have been estimated with some hourly observations
of 1.5"/hr. The concern here though, is deeper mean flow is more
parallel to allow for increased duration/training potential in the
short-term with 2-3" totals possible over the next few hours.

The greater concern for flash flooding will begin to expand in the
16-17z time frame, closer to the coast plain and toward the
Houston Metro area by early afternoon. CIRA LPW and therefore
TPW, show a strengthening of the western gulf coastal jet surging
northward at this time, before veering at/near the coast
increasing convergence well ahead of the frontal zone. Hi-Res
CAMs supported by observations of veering low level
flow/increasing temps/dewpoints coming ashore off the warm Gulf,
develop strong deeper convection from Victoria county toward the
Houston Metro, strengthening further with the push of cold frontal
convection. Training and eventual mergers (~20z) of
thunderstorms may result in hourly rates/totals of 2-2.5" with
isolated 3" totals. Overall totals of 2-4" across the coastal
plain would be close to the generally higher FFG, especially given
well below normal rains over the last month or so (5-10% of normal
per AHPS). Still, the sheer rates, particularly near the urban
settings will pose a possible flash flooding risk through early
afternoon.

Gallina

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31999418 31229386 30149385 29669402 28789530
28389659 28669744 29669815 30499743 31369588
31939494
$$
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AWUS01 KWNH 291750
FFGMPD
TNZ000-ALZ000-MSZ000-ARZ000-300000-

Mesoscale Precipitation Discussion 1170
NWS Weather Prediction Center College Park MD
1249 PM EST Wed Dec 29 2021

Areas affected...central/southern Arkansas, southwestern
Tennessee, northern Mississippi

Concerning...Heavy rainfall...Flash flooding possible

Valid 291748Z - 300000Z

Summary...A gradual increase in coverage of convection will lead
to locally excessive rainfall and potential flash flooding
initially in Arkansas before spreading eastward/downstream into
the Mid-South through 00Z.

Discussion...Earlier, weakly forced convection across northern
Mississippi produced locally heavy rainfall in areas northeast of
Grenada, MS this morning. That convection has now shifted
northeastward toward the Tennessee Valley. Additional convection
continued to expand in coverage an intensity acros central and
southwestern Arkansas currently. These storms are being
influenced by convergence on the nose of strong low-level flow
near an east-west surface boundary draped across the state. An
additional weak mid-level impulse was also likely providing lift
and resulting in increasingly heavy rain rates. Some of the
heavier convection in the short term has evolved just north of the
surface boundary, which has resulted in areas of 1-2 inch/hr rain
rates near Little Rock. The short term scenario continues to
support the locally heavier rainfall especially where
training/repeating can occur. Although rates are just shy of
1-hour FFGs, localized/sensitive areas could experience
runoff/flash-flood issues.

Over time, high-resolution guidance suggest that ongoing
convection will continue to expand in coverage while exhibiting
loose organization into clusters/linear segments amid mostly zonal
flow aloft. While any forward propagation would result in lower
residence time of heaviest rain rates in any one given location,
areas of training could contribute to 1-3 inches of rainfall in a
short amount of time (around 1 hour or so), which could lead to
flash flooding. Of particular concern is the potential for
organized convection to develop and train over areas that
experienced appreciable rainfall from convection last night and
this morning across portions of north-central and northeastern
Mississippi. These areas are a bit more sensitive and will likely
require less rainfall to cause flash flooding.

Cook

ATTN...WFO...BMX...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...SERFC...NWC...

LAT...LON 35398982 35278869 34918818 34128818 33518945
33199137 33089324 33219394 33579384 34739298
35139160

$$
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AWUS01 KWNH 300648
FFGMPD
CAZ000-301800-

Mesoscale Precipitation Discussion 1173
NWS Weather Prediction Center College Park MD
147 AM EST Thu Dec 30 2021

Areas affected...Southern California

Concerning...Heavy rainfall...Flash flooding possible

Valid 300646Z - 301800Z

Summary...Increasing rainfall intensity will likely begin to
impact the Transverse Ranges of southern CA within the next few
hours and continue through 15Z. Hourly rainfall totals between 0.5
and 1.0 inches are expected in both coastal and inland locations.
Overlap of these rates with burn scar areas could lead to flash
flooding and debris flows.

Discussion...Loops of water vapor imagery through 06Z showed a
positively tilted trough axis off of the CA coast, in the process
of closing off a low near 33N 125W. Blended TPW imagery and RAP
analysis data showed a plume of 0.8 to 1.0 inch precipitable water
values located southeast of the upper low, pointed into southern
CA from Ventura County to Orange County. Moderate to occasionally
heavy rain has been found across the region where 850 mb winds
measured between 20-30 kt, roughly orthogonal to the Transverse
Ranges. Trends in infrared satellite imagery have also shown
cooling cloud tops over the past 3-6 hours, coincident with higher
reflectivity on local radars.

Short term forecasts from the RAP show that the mid-level low will
continue the process of closing off from the main branch of the
westerlies while translating southward through 18Z. Given the
orientation of the 500 mb trough, this movement will allow colder
500 mb temperatures to overspread the southern CA coast, and
support increasing 700-500 mb lapse rates to near 7 C/km. This
process will generate a relatively shallow instability profile
that is forecast to extend up 4-5 km AGL with MUCAPE values up to
500 J/kg late tonight into Thursday morning for the coast. Subtle
increases in the low level wind along with increasing diffluence
aloft will generate increasing intensity of rainfall with perhaps
some embedded thunder as well. Rainfall totals are expected to
climb into the 0.5 to 1.0 in/hr range at times, both along the
coast and into the foothills of the Transverse Ranges below snow
levels rising to around 6000 ft AGL after 12Z. Higher rainfall
rates atop burn scars may lead to flash flooding and debris flows,
with localized 12 hour rainfall in the 3-5 inch range through late
morning.

Otto

ATTN...WFO...LOX...SGX...

ATTN...RFC...CNRFC...NWC...

LAT...LON 34761875 34741863 34681843 34611827 34531816
34481801 34431781 34421761 34351747 34341724
34281702 34241693 34161690 34151693 34111694
34051688 34031688 33911697 33781728 33661743
33371774 33241844 33591909 34111926 34401924
34621919 34741908 34751894

$$
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AWUS01 KWNH 301433
FFGMPD
SCZ000-GAZ000-ALZ000-MSZ000-302100-

Mesoscale Precipitation Discussion 1175
NWS Weather Prediction Center College Park MD
932 AM EST Thu Dec 30 2021

Areas affected...central Alabama, central Georgia, far southern
South Carolina, far east-central Mississippi

Concerning...Heavy rainfall...Flash flooding possible

Valid 301430Z - 302100Z

Summary...Occasional rain rates above 1-2 inches per hour are
expected as storms develop and migrate eastward across the
discussion area today. Flash flooding could occur as a result.

Discussion...Scattered convection continues to develop and migrate
eastward along a surface boundary located from east-central
Mississippi to near Atlanta to near Athens. Along and south of
the boundary, a warm, moist, and uncapped airmass (characterized
by 2000 J/kg MUCAPE and 1.5 inch PW values) supports deep
convection and efficient rain rates beneath the stronger storms.
Forcing aloft is fairly weak, however, given zonal flow aloft.
That zonal flow was also allowing convection to train/repeat over
wet soils. Subtle 850mb convergence near the surface boundary
should continue to support occasional convection throughout the
day. Each of the mesoscale and synoptic factors suggest a
continued flash flood threat through at least 21Z, with only a
slow southward translation of the axis of higher rain rates during
that time.

Perhaps the highest flash flood risk will exist through 18Z today
across northern portions of the MPD area from near Birmingham to
near Atlanta. In these areas, FFGs are fairly low (as low as 1
in/hr in a few spots) and soils are more susceptible to runoff.
The flash flood risk should lessen thereafter, however, as
convection migrates into areas that have been drier and are less
sensitive to heavy rain.

Cook

ATTN...WFO...BMX...CAE...CHS...FFC...JAN...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34048388 33888265 33648159 33438094 32948088
32548127 32398267 32168382 31898496 31978755
32118870 32398917 32608923 32818924 33198821
33748672 33968501

$$
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AWUS01 KWNH 302052
FFGMPD
SCZ000-GAZ000-ALZ000-310250-

Mesoscale Precipitation Discussion 1177
NWS Weather Prediction Center College Park MD
352 PM EST Thu Dec 30 2021

Areas affected...southern/eastern Georgia, southeastern Alabama,
southern South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 302050Z - 310250Z

Summary...A limited flash flood risk continues as a convective
complex with localized training of cells migrates
east-southeastward through the discussion area.

Discussion...Latest radar mosaic/MRMS imagery indicates a gradual
decrease of rain rates with convective activity within an
elongated band from roughly 25 S SEM to LOC to AGS along with a
subtle increase in forward speed. A few cells within the linear
band were training in portions of east-central Georgia, and a few
bands of convection were gradually deepening south of the band in
southern Georgia. Rain rates with most of the activity were
approaching 1-1.5 inches per hour in heavier activity.
Furthermore, the convection has now moved south of locations that
had lower FFGs due to antecedent rainfall and most areas are now
in the 2-3 inch/hr FFG thresholds. Rain rates are below these FFG
thresholds in most areas for the time being. The orientation of
the convection (particularly the aforementioned linear segments)
suggests that any remaining flash flood threat through the evening
should be limited to 1) sensitive/hydrophobic areas and/or 2)
areas where training and/or cell mergers can locally prolong the
higher rain rates. On the whole, the flash flood risk is becoming progressively more isolated with time.

Cook

ATTN...WFO...BMX...CAE...CHS...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 33548170 33318062 32918011 32118090 31578228
31068342 30968416 31418475 31468559 31408636
31618656 32288664 32778568 33268446 33358292

$$
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AWUS01 KWNH 312131
FFGMPD
AZZ000-010330-

Mesoscale Precipitation Discussion 1178
NWS Weather Prediction Center College Park MD
431 PM EST Fri Dec 31 2021

Areas affected...central to southeastern Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 312130Z - 010330Z

Summary...An advancing storm system over northwestern Mexico has
initiated a few showers and thunderstorms this afternoon, with
locally heavy rainfall and spotty/isolated flash flood risk
expected through 03Z or so.

Discussion...Deepening convection with a few lightning strikes
were recently observed ahead of a compact mid/upper wave centered
just south of the international border in northwestern Mexico.
Downstream of the low, heating has allowed for surface temps to
reach the 50s and lower 60s F, with just enough instability to
support deep convection. Cooling/ascent associated with the
advancing upper wave was also allowing for sufficient instability
to support convection. The cells are in an environment
characterized by around 500 J/kg MUCAPE and PW values ranging from
0.6-1.0 inch - highest near the center of the mid/upper low. These
storms should be fairly progressive given strong and generally
unidirectional flow aloft (exceeding 70 knots at 500mb). Despite
their forward motion, the tendency for localized training will
exist given the nature of the convective initiation, with
orientation in bands/linear segments and clusters possible. A
quick 0.5-1.0 inch could fall beneath heavier cores, which could
cause issues given 1) FFGs in the 0.5-1.5 inch/hr range and 2)
sensitive low spots/areas with burn scars.

High res models are not particularly aggressive with convective
initiation in this region, and current observations are exceeding
expectations with respect to convective coverage. Indications are
that the maximum flash flood risk in the discussion area will
persist for the next 4-6 hours until the mid-level wave
responsible for the convection exits east into New Mexico.

Cook

ATTN...WFO...FGZ...PSR...TWC...

ATTN...RFC...CBRFC...NWC...

LAT...LON 34981134 34591056 33650962 32670910 31780907
31260927 31201035 31361122 31671204 32131223
32921232 34091245 34741204

$$
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AWUS01 KWNH 081936
FFGMPD
LAZ000-TXZ000-090125-

Mesoscale Precipitation Discussion 0015
NWS Weather Prediction Center College Park MD
236 PM EST Sat Jan 08 2022

Areas affected...southeast Texas and a small part of southwestern
Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 081925Z - 090125Z

Summary...A few instances of localized flooding are possible
through the early evening as deep convection develops and drifts
northward across the discussion area.

Discussion...Radar/satellite trends suggest a continued deepening
of convection especially across the eastern portions of the
Houston Metro area, with other scattered storms over open
northwestern Gulf of Mexico waters and also northward to near
Longview. The storm were in a destabilizing airmass, with strong
buoyancy (1500-2000 J/kg MLCAPE) evident in objective analyses
along and south of a warm front located from near CLL to near BPT.
Deep layer shear isn't particularly strong in this area, though a
tendency for weak updraft rotation (owing to vorticity along the
warm front and appreciable environmental helicity) could allow for
a few cells to contain enhanced rain rates. MRMS data suggests
that this scenario is materializing just east of the Houston Metro
area, where rain rates exceeding 2 inches per hour were recently
noted.

The overall synoptic scenario supports a continued inland push of
very warm/moist air across southeast Texas and adjacent areas of
Louisiana through 01Z. PW values exceeding 1.5 inches, occasional
training, and slow-movement of cells will pose a brief/isolated
flash flood risk especially if cells can linger over
sensitive/urbanized areas for any length of time. A few localized
areas may experience 2-4 inches of rainfall in a couple hours.
FFG thresholds aren't expected to be exceeded on a widespread
basis, although heavier rainfall/training is most likely where
storms can either 1) backbuild or anchor along the warm front or
2) redevelop and train on the within the of the moist/unstable
axis. The second scenario involves potential redevelopment of
storms near or just west of the Houston Metro through the
afternoon.

Cook

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 32229385 31999332 31279310 30429312 29809287
29529300 29479419 28719573 29049663 30089663
30819645 31209614 31869534

$$
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AWUS01 KWNH 091727
FFGMPD
WVZ000-TNZ000-KYZ000-092325-

Mesoscale Precipitation Discussion 0021
NWS Weather Prediction Center College Park MD
1226 PM EST Sun Jan 09 2022

Areas affected...portions of Kentucky into West Virginia

Concerning...Heavy rainfall...Flash flooding possible

Valid 091725Z - 092325Z

Summary...Areas of excessive runoff are possible where heavy rain
can fall over areas that experienced snow over the past few days.

Discussion...A combination of lift near a cold front traversing
the region and deep convection across portions of Tennessee and
Mississippi earlier is contributing to areas of light to moderate
rainfall in a band from southwestern Kentucky eastward to West
Virginia. Locally heavier rainfall was also observed, with rain
rates approaching 0.5 inch/hr near Hopkinsville/Bowling Green.
Meanwhile, portions of the region received 4-8 inches of snow with
a system that traversed the area on January 6-7. While the
observed rain rates would not ordinarily support widespread
flooding issues, some concerns exists that the combination of
precipitation and runoff from prior snowmelt may be enough to
cause minor flooding near streams/tributaries and low-lying areas.

Areas locally heavy rainfall will continue across much of the
discussion area, but end from west to east over time. Recent runs
of the HRRR and 12Z HREF suggest that most of the precipitation
will exit Kentucky by the 22-23Z timeframe.

Cook

ATTN...WFO...JKL...LMK...OHX...PAH...RLX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38568119 38318112 37848189 37428252 37268340
36838447 36628560 36678750 36678799 36818816
37068731 37608594 37938489 37968386 38208248
38448173
$$
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AWUS01 KWNH 092019
FFGMPD
ALZ000-MSZ000-LAZ000-100112-

Mesoscale Precipitation Discussion 0022...Corrected
NWS Weather Prediction Center College Park MD
318 PM EST Sun Jan 09 2022

Corrected for geographic header

Areas affected...central/southern Alabama, southern Mississippi,
and a small part of southern Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 092012Z - 100112Z

Summary...Storms continue to shift eastward across the discussion
area. Areas of 1-2 inch/hr rain rates could cause localized flash
flooding issues through the afternoon.

Discussion...An MCS has grown upscale and accelerated eastward
from central Mississippi to central Alabama early this afternoon.
Meanwhile, additional showers and thunderstorms continue to deepen
both upstream near a synoptic front entering the Mississippi Delta
and within a warm, buoyant pre-convective airmass between Meridian
and Mobile. Strong deep layer shear was allowing for appreciable
forward motion of each of the cells in the discussion area.
Additionally, the storms are in areas that contain relatively high
FFGs (ranging from 2-3 inches/per hour). PW values in the 1.5-1.7
inch range area allowing for efficient rain rates with the
deeper/stronger convection, although the forward speed was only
allowing for 1-hour rain rates to peak at around 1-1.5 inches in a
couple spots within the past hour or so.

The greatest risk for flash flooding in the near term will reside
within a couple of regimes: 1) along the southwestern flank of the
central Alabama MCS, where orientation of storms in that area were
more parallel to deep flow and storms along the front were yet to
move through and 2) storms along a pre-frontal trough from near
JAN to near BTR, who's orientation was also slightly more
favorable for training. Although the risk of flash flooding is
expected to remain isolated, areas that can experience any
prolonged heavy rain rates may approach or exceed FFG thresholds.

Cook

ATTN...WFO...BMX...JAN...LCH...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34208578 33898541 33168562 32438571 32118635
31828700 31608785 31468840 31388910 31168965
30969034 30589126 30549213 30489259 30859233
31359153 31779106 31919073 32269028 32578990
32788924 33138841 33478773 33578702 33938635

$$
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AWUS01 KWNH 172220
FFGMPD
ALZ000-MSZ000-180317-

Mesoscale Precipitation Discussion 0037
NWS Weather Prediction Center College Park MD
519 PM EST Thu Feb 17 2022

Areas affected...eastern MS to central AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 172217Z - 180317Z

Summary...Short, training convective segments are expected to
shift eastward with time across the central MS/AL border into
central AL. Hourly rain totals to 2" with local amounts to 4"
could lead to issues in urban areas.

Discussion...While a progressive convective line is moving into
northern AL, there are some line segments that are training
between this line and the incoming cold front showing less
progression, with some hourly totals of 1.5-2" indicated by radar
in eastern MS recently. Precipitable water values of 1.5-1.8" lie
in this region per GPS data. Inflow at 850 hPa is convergent out
of the southwest at 50-60 kts, with similar effective bulk shear.
ML CAPE of 500-1000 J/kg has been shifting east with time into
western AL.

The mesoscale guidance has a variable signal for local amounts
~3". Believe that hourly totals initially should peak in the 2"
range with some potential for 4" amounts should convection train
for a couple hours before moving on. Towards the end of the
period, the upstream instability pool should be collapsing towards
the Gulf coast of AL/FL, shifting southeast and weakening, which
should cause a more rapid progression and less of a chance for
training. This forecast change in the instability also implies
that the mesoscale guidance, including the 20z HRRR, appear
somewhat too far to the north with their maxima, so the MPD area
depicted is somewhat south of the guidance. These amounts would
be most problematic in urban areas.

Roth

ATTN...WFO...BMX...HUN...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34108707 33248637 31978753 31648892 32318981
33828846
$$
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AWUS01 KWNH 281900
FFGMPD
ORZ000-WAZ000-010500-

Mesoscale Precipitation Discussion 0048
NWS Weather Prediction Center College Park MD
159 PM EST Mon Feb 28 2022

Areas affected...Washington/Oregon Coastal Ranges into Cascades

Concerning...Heavy rainfall...Flash flooding possible

Valid 281900Z - 010500Z

SUMMARY...Long duration atmospheric river event to continue
soaking parts of the Pacific Northwest with heavy rain. Another
2-4" of rainfall could lead to additional areas of flooding this
afternoon and into this evening.

DISCUSSION...A robust upper low in the northeast Pacific continues
to funnel rich subtropical moisture into the Pacific Northwest
today. The latest 12Z GFS showed PWs of 1.00"+ stretching from the
Seattle metro area on south throughout much of northwest Oregon.
These PWs throughout the highlighted region on average are
~2.5-3.0 standard deviations above normal. Integrated Vapor
Transport just off the coast is forecast to range between 600-800
kg/m/s through 03Z. The other factor of note is freezing levels
remain quite high. 12Z GFS freezing levels near Tacoma at 21Z this
afternoon are likely to hover around 8,000'. This is causing rain
to be the primary precipitation type in areas where some snowpack
resides in portions of the Cascades. Combined with strong 850mb
jet of 60-70 kts (~5 standard deviations above normal), favored
upslope locations on the windward sides of the Olympics, Cascades,
and northwest Oregon coastal range have the best odds of seeing
the heaviest rainfall rates this afternoon.

Hourly rainfall rates have generally been capped around 0.50" with
a few locations on occasion reaching 0.60"/hr. Latest 12Z GFS
forecasts continue to support a continuous 850-500mb SW flow into
southwest Washington and northwest Oregon into the evening hours.
The 12Z HREF 2"/3hr rainfall probabilities in the Cascades of
southwest Washington range between 30-40% in the 21-00Z time
frame. Much of the rugged elevated terrain in the highlighted
region has also seen 0-40cm soil moisture rise to over 90% in some
spots thanks to a wet stretch the last 48 hours. Despite the lack
of atmospheric instability, a steady fire hose of rainfall,
combined with overly saturated soils and ongoing snow melt are
likely to cause nearby creeks, streams, and rivers to continue to
swell this afternoon and into the overnight hours. This could
possibly result in spawning new areas of flooding and/or
exacerbate ongoing flooding in parts western Washington and
northwest Oregon.

Mullinax

ATTN...WFO...OTX...PDT...PQR...SEW...

ATTN...RFC...NWRFC...NWC...

LAT...LON 49172161 49062111 48892097 48452077 48132076
47832092 47602080 47432080 47372093 47182139
47052143 46912125 46572130 46272129 46112135
45662169 45482195 45532225 45692243 46072275
46212303 46032331 44842341 44902399 46112443
46952463 47482457 47712447 47952431 48112404
48062370 48042352 47892322 47712305 47342288
47252263 47412234 47632210 47922194 48252202
48472207 48802208 49082199

$$
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AWUS01 KWNH 221958
FFGMPD
ALZ000-MSZ000-LAZ000-230200-

Mesoscale Precipitation Discussion 0077
NWS Weather Prediction Center College Park MD
357 PM EDT Tue Mar 22 2022

Areas affected...West-Cental AL...Eastern & Southern MS...Ext
Northeast LA...

Concerning...Heavy rainfall...Flash flooding likely

Valid 222000Z - 230200Z

SUMMARY...Training thunderstorms and storms capable of short-term
rates up to 2.5"/hr supporting rainfall totals of 3-6" this
evening poses likely flash flooding.

DISCUSSION...Regional RADAR mosaic depicts a maturing MCV/Meso-Low
nearing Tupelo, MS from the southwest with a strong bowed segment
bulging eastward before flattening more E-W south of I-20 back
toward the SW MS and NE LA border. 19z surface analysis suggests
a weak surface wave near the SW MS corner with a more linear
squall line extending due south. 17-18z ROABs across the region
suggest increasingly south-north unidirectional flow up through 5H
with only backed winds below the boundary layer, helping to
support localized increase moisture flux convergence into stronger
rotating updrafts. Aloft, the 3H right entrance continues to lift
northward with best divergence directly above the MCV, so
divergence support will be slackening southward along the line and DPVA/height-falls will support eastward propagation of the line.
Still, the warm conveyor while narrowing in the narrowing warm
sector continues to be very deep with 1.7-1.9" TPW values and
quite unstable with MLCAPE values of 1500+ J/kg across S MS with
750-1000 values as far north as an effective warm front from STF
to GZH.

Recent EIR/Visible imagery depict numerous north-south streamers
in the warm sector with narrower updrafts trying to break through
mixed mid-levels. Streamline intersection with the southeast side
of the bowing segment has seen rapid cooling/strengthening
updraft. Strong nearly perfect orthogonal intersection with the
trailing outflow boundary and 85H winds to 70kts has maintained
fractured but still highly efficient updraft cores, given the
strength of the moisture flux and the steepness of the cold pool.
The orientation is very favorable to the propagation vectors of
the system as a whole supporting a corridor of enhanced training.
So, while the strongest cells are capable of 2-2.5"/hr rates
(with WoFS 5 min totals of .4-.5"), solid 1-1.5" totals between
will allow for sizable totals along this axis. WoFS mean QPF
suggest 3-6" with isolated higher totals over 6+". HRRR and ARW
solutions support similar totals/axis but continue to north of the observational trend. So this provides solid confidence in these
totals though likely further south. While FFG values are higher,
the instantaneous rates and 3-6hr totals of 3-5" are likely to
continue flash flooding risk from Feliciana Parish to
Jasper/Neshoba county through 02z and filtering into west-central
AL.

Further north NE MS/NW AL...
Models have been very poor with the timing of the bow segment and
have been suggesting greater northward progression of the warm
sector that has not manifest. However, strong isentropic ascent
along/head of the MCV and modest MUCAPE has provided strong
moisture flux to the region and the bowing segment has resulted in
very intense short-term rain totals of .5-1" in 5-15 minutes
generally in line with the WoFS and HRRR 5-min and instantaneous
rate values; resulting in isolated flash flooding conditions
particularly in urban centers due to impermeable surfaces. This
is then followed by a broad shield of moderate rainfall with
.25"-.33"/hr rates enhancing totals and potentially nearing longer
term FFG values, especially given FFG values are a bit lower this
area. As such, flash flooding is possible with longer duration
flooding more probable.

Gallina

ATTN...WFO...BMX...HUN...JAN...LIX...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34848749 34488612 33108632 32058723 31668786
30868908 30479129 31519146 32099043 33268942
34618917
$$
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AWUS01 KWNH 281503
FFGMPD
CAZ000-290100-

Mesoscale Precipitation Discussion 0083
NWS Weather Prediction Center College Park MD
1101 AM EDT Mon Mar 28 2022

Areas affected...Southern California Coastal Ranges

Concerning...Heavy rainfall...Flash flooding possible

Valid 281500Z - 290100Z

SUMMARY...Heavy showers will continue to advance down across the
southern California coastal ranges today. There will be a threat
for some flash flooding and debris flows in and around any of the
area burn scars.

DISCUSSION...The latest GOES-17 WV suite shows a deep layer closed
low offshore of California drifting southeastward which is
allowing for a fetch of moist southwest flow to aim into the
Transverse Ranges of southern California. This coupled with deeper
layer ascent associated with divergent flow aloft around the
southeast flank of the low center has helped to drive a band of
heavy showers inland off the Pacific Ocean and down across the
coastal ranges over the last several hours. Facilitating the heavy
shower activity is the orthogonal nature of the low to mid-level
flow relative to the higher terrain which is yielding favorable
orographic ascent.

Rainfall rates over the last couple of hours have been increasing
across Santa Barbara and Ventura counties, with an emphasis on the orographically favored Santa Ynez mountains where rainfall rates
have recently been on the order of 0.50" to 0.60"/hour. The
CIRA-ALPW data from the last few hours shows some weak subtropical
moisture tap from west of the Baja California Peninsula, and this
coupled with a 30 kt low-level jet along with the aforementioned
orographics is likely the biggest reason for the uptick in
rainfall rates.

The latest hires model guidance shows the broader upper low center
dropping down to the southeast going through this afternoon, and
this will drive the main warm/moist conveyor belt down the coast
through the remainder of the Transverse Ranges and eventually down
into the Peninsular Ranges by later today. This will allow the
heavy shower activity to encompass Los Angeles, Orange and San
Diego counties, and the western portions of San Bernadino and
Riverside counties.

The heaviest rainfall in the 15Z to 00Z time frame will tend to
focus on the San Gabriel and San Bernadino mountains where the 12Z
hires models suggest as much as 2 to 3 inches of rain will be
possible, including occasional rainfall rates of 0.50"+/hour.
Areas of Santa Barbara and Ventura counties (including the Santa
Ynez mountains) later today may also see a resurgence of heavy
shower activity and comparable rain rates as the aforementioned
upper low approaches the region.

These rain rates and storm totals may lead to a threat for some
flash flooding and debris flows in and around the more recent burn
scar areas.

Orrison

ATTN...WFO...HNX...LOX...SGX...

ATTN...RFC...CNRFC...NWC...

LAT...LON 35172021 34961972 34801905 34771860 34491817
34451739 34381703 33971671 33491661 32991640
32701631 32451674 32541715 32751718 32701719
33141744 33691824 33791862 34031896 34291947
34422033 34672076 35082060
$$
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AWUS01 KWNH 301605
FFGMPD
TNZ000-MSZ000-LAZ000-MOZ000-ARZ000-TXZ000-302203-

Mesoscale Precipitation Discussion 0087
NWS Weather Prediction Center College Park MD
1203 PM EDT Wed Mar 30 2022

Areas affected...Lower and Mid MS Valleys

Concerning...Heavy rainfall...Flash flooding possible

Valid 301603Z - 302203Z

Summary...A fast-moving line of thunderstorms expected to develop
this afternoon will track eastward through portions of the Lower
and Mid MS Valleys. Rain rates up to 2"/hr may lead to flash
flooding, particularly over more sensitive locations and urban
areas.

Discussion...Impressive, fast-moving shortwave energy tracking
eastward out of the ArkLaTex region this morning will bring large
scale forcing for ascent over the Lower to Mid MS Valleys this
afternoon. A line of showers and thunderstorms ahead of the
advancing associated cold front will likely begin to grow upscale
in coverage and intensity over the next several hours with
increasing daytime heating. The environment ahead of the line of
the storms is characterized by dewpoints around 60F, MLCAPE
between 500-1000 J/kg and PWs between 1-1.25". Through the
afternoon, increasing low level flow (60+ kts at 850 mb per latest
RAP) will surge northward higher moisture and PWs are expected to
reach 1.50"+ (near 1.75") which would be +3 sigma above the
climatological mean. MLCAPEs are also progged to rise toward
1000-2000 J/kg by 19-20Z. Boundary layer convergence is expected
to increase substantially as the trough axis sharpens and becomes
more neutrally tilted.

A long line of thunderstorms is likely to evolve, spanning from
the Lower MS Valley northward toward southern IL that will race
eastward over the course of the afternoon. The fast/progressive
nature will limit heavy rainfall threat due to reduced duration,
the ingredients and strong/intense cores will support rain rates
up to 2"/hr at times. The 12Z HREF neighborhood probabilities are
high for 1"+ hourly totals along the line with slight to moderate
signals for 2"+ hourly totals. Embedded stronger cores or bowing
segments will favor some repeating/training potential.

This rainfall in the short period could lead to isolated instances
of flash flooding particularly over more sensitive soil conditions
and urban areas.


Taylor

ATTN...WFO...JAN...LCH...LZK...MEG...PAH...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 36458978 36218864 33788926 32329021 31619156
31149370 32479322 34439245 35789170 36249109
$$
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AWUS01 KWNH 051741
FFGMPD
FLZ000-GAZ000-ALZ000-MSZ000-LAZ000-052340-

Mesoscale Precipitation Discussion 0101
NWS Weather Prediction Center College Park MD
140 PM EDT Tue Apr 05 2022

Areas affected...Portions of SE LA...Coastal MS...Southeast
AL...FL Panhandle...South-Central GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 051740Z - 052340Z

Summary...Rainfall rates of 1-2"+/hr may lead to isolated
instances of flash flooding, localized totals of 2-3+ inches.

Discussion...A mature MCS/squall line continues to progress
southeastward across portions of the Southeastern U.S., extending
from near Slidell, LA east-northeastward into Mobile and towards
Atlanta. The mesoscale environment ahead of this squall line is
characterized by SB CAPE of 500-2500 J/kg (except even lower than
500 J/kg farther north into portions of GA), PWATs of 1.5-1.8
inches (well above the 90th percentile and near the max moving
average, climatologically), and effective bulk shear of 50-60 kts.
Rainfall rates of 1-2"+/hr have been occurring in association with
this MCS/squall line all morning, and these rates are likely to
continue for at least a few more hours.

The 12z HREF suite has not done a great job so far with the
depiction of convective activity, as subsequent runs of the HRRR
have shown with a consistent run-to-run southward trend with the
southwest flank of the squall line (and decreasing QPF amounts).
Things get even trickier looking more towards the northeast end
the MCS, as instability is far more limited into north-central GA
with a large area of mainly stratiform precipitation persisting.
While the better odds for higher rainfall rates appear to be
farther south, this is also where antecedent conditions are drier
and where flash flood guidance (FFG) is appropriately higher.
Farther northeast into GA, 1-2 inches of rainfall has already
fallen so lower rainfall rates may still be supportive of some
excessive rainfall.

Isolated instances of flash flooding will be possible along and
ahead of the squall line through at least mid-afternoon, as
1-2"+/hr rainfall rates lead to additional localized totals of
2-3+ inches. Totals in excess of 3 inches are more likely to be
realized across the coastal regions of MS/AL and the FL Panhandle,
though decreasing convective organization and earlier dissipation
of convection may preclude these higher totals entirely.

Churchill

ATTN...WFO...BMX...FFC...JAN...JAX...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 33498410 33038289 32078260 30668263 30108454
30108645 30168876 30269051 31059048 30988851
31518714 32188583 33288502

$$
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AWUS01 KWNH 161204
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-161800-

Mesoscale Precipitation Discussion 0120
NWS Weather Prediction Center College Park MD
802 AM EDT Sat Apr 16 2022

Areas affected...southeastern Arkansas, northeastern Louisiana, northern/central Mississippi into central Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 161201Z - 161800Z

Summary...Occasional flash flooding is possible through the
afternoon across the discussion area.

Discussion...A complicated surface pattern resides across the
discussion area this morning. A lingering MCS continues across
much of central Alabama into northern Mississippi, with convection
beginning to refire in north-central Mississippi on the western
flank of the mature cold pool. Newer, upstream convection is
forward propagating to the southeast across southwestern Arkansas
this morning and should also enter western portions of the
discussion area in the 14Z timeframe. The pre-convective airmass
is sufficiently moist/unstable to support continued convection
(1500 J/kg MUCAPE and 1.5-1.6 inch PW, respectively) and
destabilization should continue throughout the day. Additionally, cold-pools/outflows are favorably oriented to southwesterly 850mb
flow to sustain low-level convergence amid the unstable
environment - further supporting the notion of scattered
convective activity through the afternoon.

The orientation of convection in central AL/northern MS poses the
greatest concern in the short term. The slow southward
translation of the convective bands and tendency for
backbuilding/localized training is enhancing localized rain rates
into the 1-2 inch/hr range - especially southwest of Tupelo.
These rates are approaching FFG thresholds, suggesting at least
localized potential for runoff issues that should continue through
the afternoon as instability increases. This overall regime
should shift southward toward the US 80/I-20 corridor in central
MS through 18Z.

An upstream convective complex in Arkansas near Hot Springs could
also enhance rainfall rates as it reaches western Mississippi.
Rain rates were estimated to exceed 2 inches per hour in spots
beneath this complex, and some potential for repeat convection
could emerge especially if storms can expand in coverage across
western/central Mississippi ahead of this complex. Again, a few
areas will probably exceed FFG thresholds in this scenario,
leading to a localized flash flood threat through 18Z.

Cook

ATTN...WFO...BMX...JAN...LZK...MEG...MOB...SHV...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34458999 33948875 33438798 33348716 33448634
33268566 32868544 32208534 31558527 31268579
31288693 31328803 31739001 31899126 32299218
32999238 33569223 34089182 34409096

$$
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AWUS01 KWNH 161354
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-161951-

Mesoscale Precipitation Discussion 0121
NWS Weather Prediction Center College Park MD
953 AM EDT Sat Apr 16 2022

Areas affected...eastern Oklahoma into southwestern Arkansas and
northern Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 161351Z - 161951Z

Summary...An axis of convection is expected to gradually shift
southward across the discussion area through 20Z. Occasionally
heavy rain rates could cause flash flooding in a few spots.

Discussion...Thunderstorms were generally aligned along an axis
from near Fort Smith to Monticello as of 1330Z. The storms were
focused along a fairly tight gradient between rain-cooled air to
the northeast and warm, moderately unstable conditions to the
southwest. 850mb flow was generally perpendicular to the
boundary, while steep mid-level lapse rates (ranging from
7-8.5C/km) were noted within the pre-convective airmass. These
thermodynamic factors were maintaining the axis of storms, while
flow aloft (westerly, oriented nearly parallel to the low-level
boundary) was allowing for occasional repeating/training to occur
at times. MRMS data indicates that the highest rainfall rates
were occurring in south-central Arkansas, where occasional 2-3
inch/hr rain rates were beginning to materialize. This is not
surprising as PW values are maximized in the 1.6 inch range across
the southern half of the state.

Indications are that this axis of focused convective development
will gradually shift southward across the discussion area through
20Z, eventually reaching the Arkansas/Louisiana border and the
"ArkLaMiss" area through the 15-17Z time frame. Convection should
persist through that time frame due to continued low-level
advection and convergence along the boundary in addition to
persistence of the EML plume and associated steep lapse rates
aloft. Areas that experience slow-moving and/or training
convection should continue to periodically experience rain rates
exceeding FFG thresholds (2+ inch/hr rain rates), posing a flash
flood risk. FFGs are substantially lower in east-central
Oklahoma, where 3-5 inches of rain have fallen in the past 6 hours
from near Sallisaw to Fort Smith and Greenwood. Excessive runoff
and flash flooding are possible if storms can redevelop atop these
areas.

Cook

ATTN...WFO...JAN...LZK...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 36259536 36229491 35849441 35439407 34939298
34449196 33669162 32729178 32379220 32699370
33189463 33819507 35659531
$$
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AWUS01 KWNH 161808
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-ARZ000-170000-

Mesoscale Precipitation Discussion 0122
NWS Weather Prediction Center College Park MD
206 PM EDT Sat Apr 16 2022

Areas affected...central/southern Mississippi, southwestern
Alabama, northern and eastern Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 161802Z - 170000Z

Summary...An elongated MCS will continue to pose a risk of flash
flooding through the early evening across the Deep South.

Discussion...Convection has evolved into a fairly expansive MCS
across the Deep South this afternoon, with the heaviest of
rainfall focused along an axis from near Arkadelphia, AR to about
40 miles north of Jackson, MS to near Meridian, MS. The
convection continues to remain just on the cool side of an outflow
boundary near the convective axis, but continues to be maintained
by a warm, unstable pre-convective airmass (1500+ J/kg MLCAPE and
1.7 inch PW values) and southwesterly low-level flow. Locally
embedded linear segments north of the Jackson Metro area were
encouraging enhancement of rain rates into the 1-2 inch/hr range.
Other localized areas of training/slow storm movement were also
enhancing rain rates into that range in far western Alabama and
southeastern Arkansas.

Models/observations suggest that this general axis of convection
should continue to produce occasional 1-2 inch/hr rain rates while
propagating southward through the afternoon. These rain rates
will probably cause a few issues with excessive runoff especially
in urban and low-lying areas. However, as the storms propagate
southward, they will encounter land areas that can handle more
rainfall as evidenced by increasing FFGs. Thus - expect an
already isolated flash flood risk to progressively become more
isolated through the early evening. Areas that happen to
experience the greatest degree of training and/or repeating
convection could accumulate rainfall totals nearing 3 inches
through 00Z although widespread areas of 1-2 inch rainfall amounts
are expected.

Cook

ATTN...WFO...BMX...JAN...LIX...LZK...MEG...MOB...SHV...

ATTN...RFC...ABRFC...LMRFC...SERFC...NWC...

LAT...LON 34369214 34199140 33879038 33648922 33338804
32848736 31948677 31418662 30948731 30858899
30819046 31169157 31979193 32959233 34319264

$$
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AWUS01 KWNH 181953
FFGMPD
CAZ000-ORZ000-190150-

Mesoscale Precipitation Discussion 0124
NWS Weather Prediction Center College Park MD
352 PM EDT Mon Apr 18 2022

Areas affected...coastal areas of northwestern California and
southwestern Oregon

Concerning...Heavy rainfall...Flash flooding possible

Valid 181950Z - 190150Z

Summary...Multiple rounds of convection should occur along a warm
frontal zone across the Mid-South this evening. Flash flooding is
possible - especially given anomalous rainfall that fell over the
past week.

Discussion...Thunderstorms are beginning to increase in coverage
across southern Missouri. The convection is being influenced by
both 1) a subtle shortwave trough over central Missouri and 2) the
presence of 35-45 kt south-southwesterly 850mb flow, which was
contributing to convergence and lift along a warm front bisecting
the discussion area. Weak to moderate instability was located
along and south of the front, while fairly strong mid-level lapse
rates (8C/km) were noted across the area in objective analyses. West-northwesterly steering flow aloft is oriented favorably to
the warm frontal zone to allow for increasing convective coverage
and upscale growth into clusters/linear segments while
repeating/training especially across northeastern Arkansas and
western Tennessee.

The forecast scenario suggests potential for areas of 2-3 inch
rainfall totals to occur especially across the Mid-South through
06Z. The axis of greatest convective coverage should also shift
southeastward over time as veering 850mb flow results in a shift
in the location of maximum low-level convergence. Much of the
discussion area is running at about 300-500% of normal
precipitation over the past 7 days and FFGs are in the 1-2 inch/hr
range. As storms expand, FFGs should be exceeded occasionally in
several areas. At least a few instances of flash flooding are
expected to result.

Cook

ATTN...WFO...EKA...MFR...

ATTN...RFC...CNRFC...NWRFC...NWC...

LAT...LON 42442403 42202357 41502366 40562385 40142399
40142435 40522451 42202448

$$
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AWUS01 KWNH 242049
FFGMPD
MOZ000-ARZ000-TXZ000-OKZ000-250200-

Mesoscale Precipitation Discussion 0133
NWS Weather Prediction Center College Park MD
449 PM EDT Sun Apr 24 2022

Areas affected...North TX, Eastern and Southeastern OK, far
northwest AR

Concerning...Heavy rainfall...Flash flooding possible

Valid 242048Z - 250200Z

Summary...Showers and thunderstorms developing along a slow moving
front will continue to train to the northeast through this
evening. Rainfall rates may briefly exceed 2"/hr at times,
producing 1-3" of rain with local maxima to 4". Flash flooding is
possible.

Discussion...The regional radar mosaic this aftn shows a large
area of showers with embedded thunderstorms stretching along a
slow moving front from far NE Oklahoma into parts of N Texas west
of Dallas-Fort Worth. Recent rain rate estimates from KFWS have
exceeded 1.5"/hr, and daily rainfall as measured by regional
mesonets has been more than 3 inches in a few locations. This rain
is occurring atop very dry soils due to AHPS 14-day rainfall that
is generally just 10% of normal leading to 40cm soil moisture
according to NASA SPoRT that is in the bottom 10th percentile.
This has so far limited the flooding across the region this
morning, but is priming the soils for an increased flash flood
risk.

As the aftn progresses, thunderstorms are likely to expand and
intensify. A mid-level longwave trough axis over the Four Corners
will maintain deep SW flow into the Southern Plains, through which
embedded shortwave impulses will lift northeast. Additionally, a
strengthening upper jet streak will place increasing RRQ
diffluence atop the region, and the overlap of convergence along
the front with PVA and upper diffluence will produce increasing
deep layer ascent. This forcing will impinge upon favorable
thermodynamics characterized by MUCape forecast to reach 1000-2000
J/kg and PWs surging towards 1.75", around the 90th percentile for
the date. These favorable thermodynamics will advect northward
into the front on a LLJ which should locally back to the south at
20-30kts, becoming more orthogonal to the boundary for better
ascent. This suggests that storms will likely initiate on the
boundary and lift northward, with the heaviest rainfall expected
along and just north of the front. Rain rates within this
expanding convection are progged by the HREF to reach 2"/hr, which
could exceed the 1-hr FFG.

Deep SW flow will remain parallel to the front, so despite 0-6km
winds that will be 30-40 kts, training of echoes is likely which
could enhance rainfall duration, or produce several rounds of of
heavy rain. The most robust overall convection should gradually
shift ENE with time, but regeneration back into the better
instability and along the front has the potential to produce
longer duration heavy rainfall anywhere within the MPD area. The
dry soils will continue to somewhat limit the flash flood threat,
but where training occurs, locally 4" of rainfall could occur,
leading to possible flash flooding.


Weiss

ATTN...WFO...FWD...LZK...OUN...SGF...SHV...SJT...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 36729414 36609382 36319348 35929337 35369342
34839371 34099441 33409509 32829602 32449681
32199763 32059830 32019888 32089923 32249967
32519982 32929991 33729956 34249884 34699810
36349572 36619513
$$
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AWUS01 KWNH 102014
FFGMPD
TXZ000-OKZ000-NMZ000-110200-

Mesoscale Precipitation Discussion 0184
NWS Weather Prediction Center College Park MD
412 PM EDT Tue May 10 2022

Areas affected...Southwest Texas Northward to the Texas Panhandle

Concerning...Heavy rainfall...Flash flooding possible

Valid 102009Z - 110200Z

Summary...A well-defined dryline will help focus convection during
the afternoon and evening in a region of weak deep-layer vertical
wind shear...abundant low level moisture and steep low level lapse
rates. These storms will pose a risk for flash
flooding...especially from slow moving cells or where cell mergers
occur.

Discussion...18Z surface analysis showed a well-defined dryline
separating dewpoints in the 70s from dewpoints in the teens to
lower-20s over southwest Texas with several thousand Joules per kg
of CAPE with little capping. Shortwave energy over northern
Mexico will interact with the airmass and result in increasingly
numerous storms throughout the period. The potential for cell
mergers or slow motion of cells suggests the risk for flash
flooding will increase as the number of storms
increase...especially with the environmental variables being
supportive of rainfall rates in excessive of an inch per hour.
Isolated maximum rainfall amounts of 1.5 to 2.5 inches possible
based on some of the CAM guidance and the latest WoFS runs.

The CAMS and WoFS have been depicting the potential for heavy rain
developing towards the Pecos and Rio Grande regions this afternoon
followed by the risk spreading northward and eastward along the
dryline as far north as the Texas Panhandle by late afternoon or
evening with some potential for 3-hr flash flood guidance values
to be challenged.

Bann

ATTN...WFO...AMA...EWX...LUB...MAF...OUN...SJT...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON 35400027 34729990 33319987 31960049 30430042
29280030 28900036 28680039 28930060 29110075
29340090 29550110 29700134 29820160 29820183
29820206 29810227 29760243 29650260 29570276
29240298 29070311 29000326 29180364 29470379
29870382 30340393 30850386 31320369 31930356
32460348 32800336 33860258 34810168

$$
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AWUS01 KWNH 131841
FFGMPD
TNZ000-KYZ000-MSZ000-MOZ000-ARZ000-132240-

Mesoscale Precipitation Discussion 0200
NWS Weather Prediction Center College Park MD
240 PM EDT Fri May 13 2022

Areas affected...Portions of the Mid-South

Concerning...Heavy rainfall...Flash flooding possible

Valid 131840Z - 132240Z

Summary...Slow moving, heavy downpours (2-3"+/hr) may lead to
localized flash flooding in poor drainage/urbanized areas.

Discussion...Heavy showers and thunderstorms have initiated along
a subtle stationary front, draped from north-to-south nearly
parallel to the Mississippi River from Missouri to Louisiana. Some
of the most robust convection along this front has occurred across
the Mid-South, where the mesoscale environment is characterized by
very high SB CAPE (instability) of 4000-5000+ J/kg, PWATs of
1.6-1.8 inches (near the max moving average per the JAN sounding
climatology), and very low shear (850-300 mb mean wind of 5-10
kts). This is an environment capable of very heavy rainfall, as
has been seen already with showers and thunderstorms producing
hourly rates up to 2-3"+/hr. The biggest concern with the
convective evolution this afternoon is the slow storm motion,
which may allow for localized totals to reach as high as 3-5
inches in a 2-3 hour period. The slow drift of convection towards
the SSE (with the mean wind) should prevent heavy rainfall from
lasting more than 2-3 hours in any one location.

Antecedent soil conditions are not of particularly great concern,
as soil saturation and streamflows are generally near normal (with
NASA SPoRT-LIS 0-40 cm relative soil moisture even indicated as
low as the 10-20th percentile over northwest TN and the Missouri
Bootheel). This suggests that the flash flood threat from any
heavy rainfall is relatively low and primarily relegated to poor
drainage areas and/or urbanized terrain (such as the Memphis
metro) where more than 3" in an hour or two can cause some runoff
problems.

Churchill


ATTN...WFO...LSX...MEG...PAH...

ATTN...RFC...LMRFC...NCRFC...NWC...

LAT...LON 37768993 37258960 36148933 35078939 34238997
34159075 34559092 35579044 36489035 37149033

$$
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AWUS01 KWNH 142055
FFGMPD
OHZ000-KYZ000-INZ000-ILZ000-150052-

Mesoscale Precipitation Discussion 0204
NWS Weather Prediction Center College Park MD
453 PM EDT Sat May 14 2022

Areas affected...Portions of Northern Kentucky...Southern Indiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 142052Z - 150052Z

Summary...Scattered showers and thunderstorms will be capable of
1-2"+/hr rates through the early evening hours. Localized flash
flooding is possible.

Discussion...Pulse-like, scattered convection has blossomed across
much of the Ohio Valley this afternoon, as an anomalously moist
environment has allowed for efficient warm rain processes to
dominate (freezing levels well over 10k ft). The mesoscale
environment is characterized by SB CAPE of 2000-2500 J/kg, PWATs
of 1.2-1.4 inches (at or above 90th percentile, per ILN sounding
climatology), and little to no effective bulk shear (850-300 mb
mean wind near 10 kts). An upper-level low centered just to the
east-southeast is largely responsible for elevated lapse rates,
particualrly from 0-3km. This has allowed for pulse thunderstorm
activity to produce localized rainfall rates as high as 1-3"/hr
with slow storm motions, and given the ample mounts of available
moisture and instability this scattered activity will likely
continue through the early evenings hours.

Hi-res CAMs have performed particularly poorly with this air mass,
largely underdoing both coverage and intensity of convective
activity. The HRRR has been particularly poor today, despite more
frequent runs and ongoing radar assimilation. Current trends will
support localized 1-2"+/hr rates and corresponding totals as high
as 2-4 inches in a relatively short period. Some of the more
vigorous activity has already started to become outflow dominate,
which should allow for cell mergers and outflow boundary
collisions to lead to additional convective development (as well
as some repeating of heavy rates). As more and more storms get
cut-off by their cold pools this evening, expect activity to wane
fairly rapidly with decreasing available instability and
increasing inhibition.

Churchill

ATTN...WFO...ILN...ILX...IND...JKL...LMK...PAH...RLX...

ATTN...RFC...OHRFC...NWC...

LAT...LON 40038740 39988669 39718612 39378564 39168525
39108520 38978455 38768397 38538340 38418295
37858309 37848480 37688596 38228696 38618746
39418753 39808758

$$
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AWUS01 KWNH 142151
FFGMPD
MOZ000-ARZ000-150230-

Mesoscale Precipitation Discussion 0205
NWS Weather Prediction Center College Park MD
551 PM EDT Sat May 14 2022

Areas affected...Portions of Northern Arkansas...South-Central
Missouri

Concerning...Heavy rainfall...Flash flooding possible

Valid 142150Z - 150230Z

Summary...Scattered, slow moving thunderstorms will produce
rainfall totals of 2-3+" locally through the evening. An isolated
instance or two of flash flooding is possible.

Discussion...A relatively small area of percolating convection is
showing signs of organization this afternoon, producing rainfall
rates locally of 1-2"+/hr. Slow effective storm motions (10 kts or
less) and a tendency for backbuilding towards the west (upshear)
have allowed for a nearly stationary presentation of convection,
posing a flash flood threat as these heavy rates repeat. The
mesoscale environment is characterized by very high instability
(4000-5000+ J/kg of SB CAPE), elevated precipitable water values
(1.3-1.5 inches, near the 90th percentile per LZK sounding
climatology), and effective bulk shear of 20-30 kts (acting to
organize and allow for persistence of updrafts).

Like most convective activity as of late, hi-res CAMs are tending
to represent the ongoing convection rather poorly. While the
amount of convective coverage by the HRRR is decent, it is not
intense enough and appears to try to dissipate activity too
quickly. Given radar/satellite trends (merging of activity, still
cooling cloud tops) think there's at least a few hours left of
thunderstorm activity before becoming primarily outflow dominate.
This should coincide with waning instability and increasing CIN.

While some of the area may be able to handle these heavy rainfall
rates, portions of southern MO and northern AR have rather low FFG
(less than 2 inches over 1-3 hour period) due to recent rainfall.
These areas will be particularly vulnerable to any flash flood
threat, as convection may be able to move east a bit with the mean
wind (depsite the tendency to backbuild westward into higher
instability).

Churchill

ATTN...WFO...LSX...LZK...PAH...SGF...TSA...

ATTN...RFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 38269182 38099129 37839118 37609114 37149119
36339138 36049172 35759174 35609222 35899315
36109392 36529369 36989347 37609286 37859256
38109222

$$
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AWUS01 KWNH 191810
FFGMPD
INZ000-ILZ000-MOZ000-200008-

Mesoscale Precipitation Discussion 0216
NWS Weather Prediction Center College Park MD
209 PM EDT Thu May 19 2022

Areas affected...Central/Southern MO...South-Central
IL...Southwest IN

Concerning...Heavy rainfall...Flash flooding possible

Valid 191808Z - 200008Z

SUMMARY...Showers and thunderstorms will be increasing in coverage
going through the mid to late-evening time frame. Very heavy
rainfall rates are expected with the activity, and this combined
with locally repeating cells will foster some areas of flash
flooding potential.

DISCUSSION...The latest GOES-16 visible satellite imagery shows a
very well defined and strong MCV advancing east-northeast across
southwest MO early this afternoon which will be moving steadily
into the lower OH Valley region going through the afternoon and
evening hours. This energy will be interacting with a diffuse
quasi-stationary front and the pooling of moist/unstable air up
from the Mid-South to promote an expansion of showers and
thunderstorms over the next several hours.

Already the airmass is moderate to strongly unstable across areas
of central/southern MO and over through southern IL and southern
IN in vicinity of the boundary with MLCAPE values of 2000+ j/kg
seen locally, and with strong diurnal heating continuing to favor
positive hourly CAPE differentials. PWs across the region overall
are slightly elevated with values of 1.5 to 1.6 inches which are
about 1.5 standard deviations above normal.

There is a fairly robust cluster of convection already over
southwest MO which should generally grow upscale over the next few
hours given the favorable thermodynamic environment, convergent
low-level flow around the eastern flank of the MCV, and also
interaction with the aforementioned front which will yield some
additional forcing. There may also be some additional west/east
oriented clusters of convection that develop downstream of the MCV
across south-central IL and southwest IN given the front and the
increasing warm air advection pattern ahead of the MCV. Later this
afternoon and into this evening, the core convection with the MCV
will likely impact areas of south-central IL and southwest IN as
well.

Very heavy rainfall rates of as much as 2 inches/hour are expected
with the stronger cells, and given some concerns for repeating
cells, some storm totals may locally approach 4 to 5 inches. Some
pockets of flash flooding will be possible given the high rainfall
rates and potential for these heavier rates to get into some of
the more sensitive urban settings. Will continue to closely
monitor.

Orrison

ATTN...WFO...ILX...IND...LMK...LSX...PAH...SGF...

ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON 39438783 39348662 38858630 38198686 37788928
37409041 37199133 36999261 37159369 37909349
38709152 39188952
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AWUS01 KWNH 241950
FFGMPD
VAZ000-NCZ000-250100-

Mesoscale Precipitation Discussion 0243
NWS Weather Prediction Center College Park MD
349 PM EDT Tue May 24 2022

Areas affected...Eastern North Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 241948Z - 250100Z

Summary...Slow moving thunderstorms developing along a warm front
will train to the east through the evening. Rainfall rates of up
to 2"/hr at times may produce 1-3" of rainfall with locally higher
amounts. Isolated flash flooding is possible.

Discussion...Recent GOES-E IR imagery this afternoon shows an area
of rapidly cooling cloud tops extending along a warm front and
into the associated warm sector across eastern North Carolina. The
recent WPC surface analysis depicted a wave of low pressure moving
across North Carolina along the eastward extending warm front,
with both the surface wave, the warm front, and a weak mid-level
impulse providing ascent to the area. PWs within the warm sector
were measured by GPS observations to be above 1.8", well above the
90th percentile for the date according to the SPC sounding
climatology, with SBCape measured by the RAP analysis eclipsing
2000 J/kg within the warm sector. These extremely favorable
thermodynamics were supporting rainfall rates that were measured
via KMHX WSR-88D to be 1.5-2"/hr, which has produced FLASH QPE-FFG
ratios of nearly 100% already, and it is likely these rates will
continue into the evening.

As the event unfolds into the evening, convection is likely to
expand across eastern North Carolina downstream of the associated
cold front. 0-6km mean winds are forecast to be relatively quick
at 15-20 kts, but the mean flow remaining parallel to the warm
front should allow for periods of short-term training leading to
multiple rounds of heavy rainfall. Additionally, bulk shear of
20-25 kts could support modest storm organization, and as RAP
forecast Corfidi vectors drop to around 5 kts, some back-building
into the greater instability is likely which could prolong the
temporal period of 2"/hr rainfall rates. FFG across the region is
generally 2-3"/3hrs, and it is possible that where the heaviest
rainfall trains, 1-3" of rainfall with locally higher amounts is
possible which is reflected by by the HREFv3 3-hr FFG exceedance
probabilities peaking near 50% through 00Z this evening.

As the entire system moves eastward, the flash flood risk should
generally wane as warm cloud depths lower and the best ascent
shifts offshore. However, isolated flash flooding is possible
through the evening as the favorable thermodynamics resupply from
the warm sector until the associated cold front pivots eastward
later this evening, and the high res-models are in generally good
agreement that the flash flood risk is short fused through the
evening.


Weiss

ATTN...WFO...AKQ...MHX...RAH...

ATTN...RFC...SERFC...NWC...

LAT...LON 36597630 36317574 36197559 35627545 35227554
35067586 34857624 34787668 34827724 34947759
35057778 35407779 35887746 36187724 36427698
36587664

= = =
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AWUS01 KWNH 021932
FFGMPD
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-030100-

Mesoscale Precipitation Discussion 0287
NWS Weather Prediction Center College Park MD
330 PM EDT Thu Jun 02 2022

Areas affected...NYC, Philadelphia, D.C./Baltimore Metros and
Surrounding Areas

Concerning...Heavy rainfall...Flash flooding possible

Valid 021930Z - 030100Z

Summary...Heavy showers and thunderstorms will be capable of
1-3"/hr rates through the evening hours. Localized totals up to
2-4 inches may lead to run off concerns, possible flash flooding.

Discussion...Convective activity has been building this afternoon
across the higher terrain of north-central Appalachia, along and
ahead of an approaching cold front. The eastward progression of
the cold front (and corresponding 30-35 kts deep layer mean wind)
will allow for storm movement into the populated I-95 corridor
through the late afternoon and evening hours, affecting the urban
centers of New York City, Philadelphia, and Washington
D.C./Baltimore. The mesoscale environment is characterized by MU
CAPE of 1000-3000 J/kg, PWATs of 1.5-1.7 inches (above the 90th
percentile, per IAD/OKX sounding climatology), and effective bulk
shear of 30-45 kts. Scattered to numerous coverage is expected,
potentially allowing for some linear organization of convection
while maintaining discrete rotating updrafts capable of very heavy
rainfall rates of 1-3"/hr. With some discrete activity also
beginning to initiate in the vicinity of the urban areas well
ahead of the cold front, there is potential for repeated rounds of
heavy rainfall over some of the more vulnerable urbanized terrain
(leading to localized totals of 2-4" over a short a period as 2-3
hours). So while the potential for training convection will be
limited (mean wind nearly perpendicular to front, relatively fast
20-30 kts storm motion), the localized repeating nature of storms
with high sub-hourly totals (with discrete convection already
producing instantaneous precipitation rates as high as 2-5"/hr,
per MRMS) will present a threat of localized flash flooding,
particularly across the urban centers.

Churchill

ATTN...WFO...AKQ...CTP...LWX...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 41337425 41217371 40897337 40447386 40097408
39797483 39327508 38487521 38007641 38287725
38597762 38877782 39377752 39767701 40087617
40597547 41087494

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AWUS01 KWNH 152043
FFGMPD
WIZ000-ILZ000-MOZ000-MNZ000-IAZ000-160230-

Mesoscale Precipitation Discussion 0361
NWS Weather Prediction Center College Park MD
441 PM EDT Wed Jun 15 2022

Areas affected...eastern IA, far northwest IL, southern and
central WI

Concerning...Heavy rainfall...Flash flooding possible

Valid 152039Z - 160230Z

Summary...Increasing coverage of thunderstorms ahead of a slow
moving front will begin to train southwest to northeast this aftn.
Rainfall rates within deepening convection could exceed 2"/hr at
times. Flash flooding is possible.

Discussion...The GOES-E visible satellite imagery this aftn shows
rapidly building Cu with some overshooting tops expanding across
northeast IA and into WI. This is indicative of deepening
convection noted in the regional radar mosaic, and is a result of
a shortwave noted on the GOES-E WV imagery pivoting across western
MN. The impingement of this shortwave combined with intensifying
upper diffluence within the RRQ of an approaching jet streak will
drive increasingly impressive deep layer ascent, aided by at least
modest isentropic upglide as the low-level flow surges northward
into the front. While this front will likely move little into the
evening, it will continue to serve as a focus for low-level
convergence with additional thunderstorm development. This could
lead to at least short-term training of heavy rain rates as the
mean cloud 850-300mb wind lies parallel to this boundary, despite
reaching speeds of 40 kts.

As the best ascent shifts slowly eastward, it will increasingly
overlap strong thermodynamics to support heavier rain rates
through deepening convection. SPC RAP analyed MLCAPE is 2500-3000
J/kg in eastern IA and southern WI, with PWs measured by GPS of
1.75-2.0 inches. A special 18Z sounding from GRB measured a
melting level of over 12,000 ft, well above the 90th percentile
for mid-June, which combined with the high PW/CAPE environment
will support a combination of both bergeron and warm-rain
processes to drive rain rates which could exceed 2"/hr later this
aftn according to the HREF. While the high-res guidance suggests
the front and associated convection should translate eastward with
time through this evening, continued development into the better
instability combined with training of these heavy rain rates could
produce 1-3" of rainfall in many areas, with locally higher
amounts possible.

Recent rainfall across this region has been well above normal
according to AHPS, especially in southern/central WI where pockets
of more than 300% of rainfall has fallen in the past 7-days. This
has raised 40cm soil moisture to above the 80th percentile
according to NASA SPoRT, and reduced FFG to 1-1.5"/1hr and
1.5-2"/3hrs. The HREF indicates the likelihood of this being
exceeded increasing to above 30% later this aftn, suggesting at
least an isolated flash flood risk, especially where the best
training can occur across any of the more saturated/impermeable
surfaces.

Weiss

ATTN...WFO...ARX...DMX...DVN...GRB...LOT...MKX...

ATTN...RFC...NCRFC...NWC...

LAT...LON 45158913 45148834 44768783 44328774 43898774
43498789 43118792 42748790 42558803 42488833
42308872 42138916 41968971 41709034 41399072
41039105 40719131 40559173 40569216 40819238
41769235 42959211 43659164 44499068

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AWUS01 KWNH 211734
FFGMPD
TXZ000-COZ000-NMZ000-AZZ000-212331-

Mesoscale Precipitation Discussion 0387
NWS Weather Prediction Center College Park MD
132 PM EDT Tue Jun 21 2022

Areas affected...New Mexico, eastern Arizona

Concerning...Heavy rainfall...Flash flooding likely

Valid 211731Z - 212331Z

Summary...Occasional instances of flash flooding are expected this
afternoon as deepening, slow-moving convection forms initially
along ridge lines and high terrain in the discussion area.

Discussion...Recent visible satellite imagery indicates gradually
deepening convection beginning to form along higher-terrain areas,
with radar echoes beginning to develop beneath the cumulonimbus
towers. The deepening towers were being encouraged by a couple of
factors, including: 1) strong solar insolation - especially along
and west of the I-25 corridor, 2) subtle lift from vorticity
maxima embedded in very weak southerly flow aloft across central
New Mexico and adjacent areas of northern Mexico, and 3) a
co-located, nearly stationary plume of mid-level moisture across
the southern Rockies. PW values in the 0.5-1.2 range (higher in
southwestern New Mexico) will likely encourage locally heavy
rainfall rates (exceeding 1 inch/hr at times), while slow/erratic
movement will enhance rainfall rates at times due to very weak
flow aloft (less than 15 knots below 500mb).

Flash flooding is most likely where deep convection can form atop
low-lying, sensitive terrain areas this afternoon. FFG thresholds
are fairly low given impervious soils and recent rainfall from
storms in the past week, and thresholds (currently in the 0.75-1.5
inch/hr range west of I-25) should be readily exceeded beneath
heavier thunderstorm cores. Localized burn scars from recent fire
activity will also enhance runoff beneath storms. Convection
should be outflow dominant and also diurnally driven, with the
overall risk continuing through at least 00Z. Additionally, the
greatest flash flood risk exists across southwestern New Mexico
and far southeastern Arizona where PW values are highest (and
thunderstorms will be more efficient).

Cook

ATTN...WFO...ABQ...EPZ...FGZ...GJT...PSR...PUB...TWC...

ATTN...RFC...CBRFC...WGRFC...NWC...

LAT...LON 38240618 37890560 37030540 35630569 34190606
32850659 32180664 31790656 31720685 31720765
31470809 31330829 31340978 31321074 31341109
31501165 31941140 32641089 33261037 33871015
34691059 35320969 36450931 37570840 38100728


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AWUS01 KWNH 222158
FFGMPD
COZ000-NMZ000-AZZ000-230400-

Mesoscale Precipitation Discussion 0392
NWS Weather Prediction Center College Park MD
557 PM EDT Wed Jun 22 2022

Areas affected...Northwest New Mexico

Concerning...Heavy rainfall...Flash flooding possible

Valid 222200Z - 230400Z

Summary...Showers and thunderstorms developing ahead of a
shortwave will increase in coverage and intensity this afternoon.
Rainfall rates may at times approach 1"/hr. Flash flooding is
possible.

Discussion...The regional radar mosaic this afternoon depicts
rapidly increasing coverage of showers and thunderstorms across
much of northwest New Mexico and northeast Arizona, generally
north of the Mogollon Rim. This activity is building in response
to burgeoning ascent through PVA and subtle height falls ahead of
a shortwave noted on the GOES-E WV imagery lifting along the NM/AZ
border. This shortwave is impinging upon a thermodynamic
environment characterized by SBCAPE of 500-1500 J/kg according to
the SPC RAP analysis, and PWs measured by GPS observations of
0.75-1", around the 90th percentile for the date. Convection
within this environment has already produced radar-estimated rain
rates of more than 1"/hr on the KABX WSR-88D, leading to MRMS
FLASH response in the QPF-FFG ratio fields of locally more than
150%.

As this shortwave continues to pivot northward this aftn, it will
work in tandem with the persistent low-level SE flow to expand and
intensify convection across the region. While the primary
mechanism for thunderstorm development is likely to be the
shortwave acting upon the greater instability, there is a subtle
700mb convergence axis noted in RAP fields near the CO/NM border
which could produce some locally enhanced ascent as well. Along
and south of this boundary, the high-res, including the recent
runs of the HRRR and the UA WRF RR, suggest thunderstorms will
persist into the evening, with rain rates reaching 0.5"/hr or more
at times. Mean cloud layer winds of 15-20 kts may limit the
temporal duration of heavy rainfall, but where repeated rounds of
thunderstorms occur, or where some storm organization can occur
through 0-6km bulk shear of 30-40kts to enhance storm development
and lengthen the duration of these rates, rainfall could reach 2"
in some locations.

This region has experienced well above normal rainfall recently,
noted by AHPS 7-day departures that are more than 600% above
normal, producing 0-40cm soil moisture that is above the 98th
percentile according to NASA SPoRT. This has compromised FFG to as
low as 1-1.5"/3hrs. Where the heaviest rain rates occur,
especially atop any of the most saturated soils or atop any recent
burn scars, flash flooding is possible through this evening.


Weiss

ATTN...WFO...ABQ...GJT...

ATTN...RFC...CBRFC...WGRFC...NWC...

LAT...LON 37000782 36990687 36640648 35860655 34960695
34100726 33600772 33370828 33370873 33710903
34840904 35940899

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AWUS01 KWNH 231942
FFGMPD
COZ000-UTZ000-240130-

Mesoscale Precipitation Discussion 0395
NWS Weather Prediction Center College Park MD
340 PM EDT Thu Jun 23 2022

Areas affected...eastern Utah, western Colorado

Concerning...Heavy rainfall...Flash flooding possible

Valid 231939Z - 240130Z

Summary...Showers and thunderstorms will increase in coverage
across Utah and Colorado this afternoon. This convection may
support rainfall rates of more than 0.5"/hr at times. Isolated
flash flooding is possible, especially across slot canyons and
washes.

Discussion...The GOES-E visible imagery this afternoon clearly
indicates a spin associated with a mid-level closed low over the
Great Basin. East of this closed low, and within a region of
impressive mid-level divergence, Cu and TCu is rapidly developing
across Utah and Colorado, associated with deepening convection.
The regional radar mosaic indicates expanding reflectivity above
40dBZ embedded within many of these cores, which is associated
with radar-estimated rainfall rates of 0.5-1"/hr on KICX WSR-88D.
Already some instances of flash flooding have been reported across
Utah near Capitol Reef NP, and more of this is possible through
the afternoon.

As the upper low shifts eastward, ascent within the region of best
divergence will intensify across the Four Corners region. This
lift will impinge upon favorable thermodynamics for heavy rain
noted by PWs measured by GPS of 0.5-0.75", around the 75th
percentile for the date, 850mb dew point temperatures as high as
+11C in western CO, and SBCAPE of 500-1500 J/kg according to the
SPC RAP analysis. While there is a clear demarcation of some drier
air evident in the GOES-E WV imagery shifting northeast from NV/AZ
which will eventually erode the PWs by this evening, low-level
flow out of the SW will offset this erosion of moisture and
instability for the next several hours, likely resulting in an
increase of convective coverage. While the high-res is, once
again, struggling to handle the ongoing activity, the recent HRRR
and UA WRF are at least subtly capturing the more widespread
activity already occurring, and suggest a continued increase into
the late aftn. Rain rates within this convection will likely reach
0.5"/hr on many occasions, with the HREF probabilities suggesting
at least a low-end threat for 1"/hr rates near the CO/UT border
before the drier air advects into the region.

Storm motions are expected to remain modest at 10-15 kts to the
northeast. However, convection that will at least initially be
tied to terrain features potentially resulting in nearly zero
storm motions at times. With 0-6km bulk shear progged at 25-30
kts, some weak organization is also possible, which would help
drive storms off the terrain, but also potentially increase
rainfall rates. Soils around the area feature pockets of well
above normal soil moisture according to NASA SPoRT, so any heavy
rainfall across these soils could produce flash flooding. However,
the greatest risk through the aftn will occur across any slot
canyons, dry washes, or where storms linger along sensitive
terrain features.


Weiss

ATTN...WFO...GJT...SLC...

ATTN...RFC...CBRFC...NWC...

LAT...LON 40860811 40410705 39870684 39080699 38420729
37830770 37550804 37100865 37030953 37071054
37231146 37531177 38041208 39111195 39791151
40741030 40850937

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AWUS01 KWNH 261854
FFGMPD
PAZ000-MDZ000-VAZ000-WVZ000-OHZ000-TNZ000-KYZ000-270051-

Mesoscale Precipitation Discussion 0412
NWS Weather Prediction Center College Park MD
252 PM EDT Sun Jun 26 2022

Areas affected...West Virginia, eastern Kentucky, western
Pennsylvania, and southeastern Ohio

Concerning...Heavy rainfall...Flash flooding possible

Valid 261851Z - 270051Z

Summary...An axis of deepening convection will move slowly
eastward across the discussion area this afternoon, posing a flash
flood risk especially in sensitive areas.

Discussion...Solar heating was occurring in the wake of early
morning convection that has now reached the West Virginia/Virginia
border region. That heating has enabled a rebound of
surface-based instability into the 1500-3000 J/kg range amid weak
inhibition and subtle surface convergence. Isolated thunderstorms
have formed and areas of 1 inch/hr rainfall rates were noted
already beneath heavier cores in eastern Kentucky and southeastern
Ohio.

Convective coverage should continue to increase through the
afternoon hours. Furthermore, slow easterly storm motions (around
10-15 knots) will help enhance locally heavy rainfall rates above
1-1.5 inch/hr, potentially approaching 1-hour FFG thresholds in a
few locations.

The above scenario suggests that isolated instances of flash
flooding will exist through peak heating hours. The convective
(and flash flood) threat will probably continue through the early
evening as another surface front (near the Indiana/Ohio border)
approaches the region through tonight.

Cook

ATTN...WFO...CLE...CTP...ILN...JKL...LMK...LWX...MRX...PBZ...
RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...NWC...

LAT...LON 41248001 41247900 40977845 40247844 39497865
38327942 37318046 36638176 36558345 36938457
37818416 38388346 39238265 40098199 40818112


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AWUS01 KWNH 291934
FFGMPD
AZZ000-UTZ000-300132-

Mesoscale Precipitation Discussion 0415
NWS Weather Prediction Center College Park MD
334 PM EDT Wed Jun 29 2022

Areas affected...Arizona and Southern Utah

Concerning...Heavy rainfall...Flash flooding possible

Valid 291932Z - 300132Z

Summary...Slow moving thunderstorms this afternoon will be capable
of producing intense rain rates and localized flash flooding.

Discussion...Weak southerly flow around the periphery of a weak
upper ridge centered over the AZ/NM border will allow for slightly
above normal moisture to lift northward through the outlook
region. PW values approaching 1-1.25" were analyzed from the
latest blended TPW product, which is between 1-2 standard
deviations above normal, with the best axis from southern AZ
through western AZ and into southwest UT. The latest mesoanalysis
showed between 1000-1500 J/kg of SBCAPE available and with peak
heating underway, convection is beginning to develop and recent IR
cloud tops show quick cooling with the deeper convection over
northern AZ and southern UT.

Through the rest of the afternoon and early evening, guidance
shows potential for scattered thunderstorms initially developing
off the terrain then moving gradually north/northeast through this
evening. HREF probabilities show moderate signal for 0.5"/hr rates
through about 02Z, particularly over central/northern AZ into
southern UT. The last several runs of the HRRR show a fair amount
of coverage of showers/storms with the isolated pockets of intense

0.5" hourly totals). This intense rainfall could lead to

localized flash flooding, particularly any sensitive burn scars,
slot canyons, dry washes, and small streams.

Taylor

ATTN...WFO...FGZ...GJT...PSR...SLC...TWC...VEF...

ATTN...RFC...CBRFC...NWC...

LAT...LON 38621319 38481108 36691084 35701081 34121032
32271079 32681348 35741395 37171372 38091371


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AWUS01 KWNH 301801
FFGMPD
COZ000-NMZ000-AZZ000-UTZ000-302357-

Mesoscale Precipitation Discussion 0419
NWS Weather Prediction Center College Park MD
200 PM EDT Thu Jun 30 2022

Areas affected...northern through eastern Arizona, southeastern
Utah, western/central Colorado, and far western New Mexico

Concerning...Heavy rainfall...Flash flooding likely

Valid 301757Z - 302357Z

Summary...Deepening, slow-moving convection along a mid-level
moist axis should provide impetus for a few areas of flash
flooding this afternoon and early evening.

Discussion...Radar/satellite imagery indicates the presence of
deepening convection along a general axis from the White Mountains
in east-central Arizona northward through higher terrain in
central Colorado. Most of the initial convection was focused
along ridgelines and terrain-favored areas over the past hour or
so. The storms are developing within a mid-level moist axis
across the region and also aided by 1) continued surface heating
and 2) subtle influence of mid-level shortwave troughs traversing
the region. Steep lapse rates and 0.5-0.8 inch PW values were
allowing for outflow dominant convection with areas of locally
heavy rainfall. Additionally, weak flow aloft (generally
southwesterly but less than about 15 knots) was allowing for
slow/erratic storm motions and rain rates already exceeding 0.25
inch/hr rain rates (estimated from MRMS) near the White Mountains
and beneath other isolated convection in south-central Utah and
central Colorado.

As typical for the time of year, excessive runoff will cause
issues with flash flooding beneath areas of thunderstorm activity
as convection expands through the afternoon hours. The most
susceptible areas will exist in/near burn scars and near other
low-lying areas. FFG thresholds are generally in the 0.75-1.5
inch/hr range, which should be exceeded occasionally beneath the
heavier cores. Much of the convective activity prompting the
flash flooding should be diurnally driven, with the localized
flash flood risk extending through at least 00Z this evening.

Cook

ATTN...WFO...ABQ...BOU...EPZ...FGZ...GJT...PSR...PUB...SLC...
TWC...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON 40820960 40740749 40810582 40370512 39570518
38830582 38250718 36890797 35530769 34090752
33180772 32980797 33300964 33481038 33901126
34581211 35781220 37221213 38081241 38911192
40551067

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AWUS01 KWNH 011624
FFGMPD
SCZ000-GAZ000-012200-

Mesoscale Precipitation Discussion 0423
NWS Weather Prediction Center College Park MD
1224 PM EDT Fri Jul 01 2022

Areas affected...Coastal Lowcountry of Georgia and South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 011623Z - 012200Z

Summary...Coastal low pressure will bring heavy rain to the coasts
of Georgia and South Carolina through this evening. Rainfall rates
of 1-2"/hr will likely train onshore, leading to instances of
flash flooding.

Discussion...An area of low pressure is clearly evident on the
regional radar mosaic this morning as a closed swirl of
reflectivity just east of Tybee Island, GA. This circulation has
become better organized this morning along an inverted trough, and
is responsible for heavy rainfall exceeding 4 inches that fell
near Chatham, GA overnight. In the vicinity of this low, cooling
cloud tops are occurring just offshore, with a stripe of enhanced
upper diffluence noted in the GOES-E WV imagery stretching from
northern GA into eastern NC. The 12Z U/A sounding out of KCHS
measured a PW of 2.11 inches, above the 90th percentile for the
date, with a freezing level approaching 15,000 ft and a mean
700-500mb lapse rate of 5.5C/km. These together with MUCAPE around
1000 J/kg imply efficient warm rain processes, and radar-estimated
rain rates from KCLX have been over 1.5"/hr this morning.

As the low continues to move slowly northeast along the coast
through this aftn, it is likely to consolidate and at least subtly
strengthen. As this occurs, pinched flow northeast of the center
will help push the 850mb LLJ to 20 kts out of the southeast. This
will originate near the Gulf Stream, transporting the warm, more
moist and unstable air onshore, helping to resupply favorable
thermodynamics to the area through the aftn. The combination of
increasing convergence on the nose of the LLJ, any frictional
convergence near the coast, and broad upper diffluence will drive
pronounced ascent, leading to increasing coverage of showers and
thunderstorms. With the thermodynamics likely to remain extremely
favorable, this will support an intensification of rain rates
which could exceed 2"/hr at times as shown by the HREF
probabilities and HRRR sub-hourly precipitation forecasts.

The heaviest rainfall is likely along the immediate coast
northeast of the low, which could receive more than 3" of
rainfall. This is where the best training potential of these heavy
rates exists as upwind propagation vectors become increasingly
opposed to the mean flow. This indicates the likelihood for
backbuilding of cells into the offshore instability with these
subsequently training onshore. However, additional heavy rain is
likely near and just west of the low center where storm motions
will slow to less than 5 kts, while still containing impressive
rain rates. The FFG across the area is generally 2-3"/1hr and
3-4"/3hrs, which the HREF indicates has a 20-30% chance for
exceedance through late this aftn, suggesting at least isolated
flash flooding in urban areas or where the most efficient training
occurs.

While this MPD is only valid through early evening, additional
MPDs may be needed for the continued flash flood threat into
tonight as the low continues to trek up the coast.


Weiss

ATTN...WFO...CHS...

ATTN...RFC...SERFC...NWC...

LAT...LON 33217985 33137957 32987946 32777974 32448011
32128060 31798090 31548110 31548127 31858142
32138147 32478129 32768103 33098044 33198018


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AWUS01 KWNH 011737
FFGMPD
MSZ000-LAZ000-TXZ000-012300-

Mesoscale Precipitation Discussion 0424
NWS Weather Prediction Center College Park MD
137 PM EDT Fri Jul 01 2022

Areas affected...Upper Texas Coast, Southwest Louisiana

Concerning...Heavy rainfall...Flash flooding likely

Valid 011736Z - 012300Z

Summary...Training showers and thunderstorms in the vicinity of a
weakening low pressure trough and MCV will produce rain rates of
2"/hr or more through this evening. Where the most significant
training occurs, flash flooding is likely.

Discussion...An MCV and accompanying shortwave, the remnants of
what was once a tropical invest area, continue to lift north near
the LA/TX border this aftn. This MCV will continue to slowly lift
north into the evening, providing ascent into an extremely
favorable, tropical, environment for heavy rainfall. PWs measured
by GPS are above 2.25" across most of the Upper Texas coast and
into Louisiana, with MLCAPE 500-1500 J/kg analyzed by the SPC RAP.
Heavy rain has been persistent in this environment this morning,
with a few mesonet stations measuring 4-7" already today near Port
Arthur, TX leading to several reports of flash flooding.

As the aftn progresses, this MCV should continue to lift off to
the north/northeast, but may weaken with time. However, increasing
low-level flow noted by 850mb winds progged to reach 20-25 kts
will continue to supply ample moisture and instability onshore. It
is likely that as this feature lifts north, the intensifying
inflow will allow better thermodynamics to shift farther inland,
to expand the coverage of heavy rainfall. However, is it evident
that some rain-cooled more stable air has developed in the
vicinity of Port Arthur, to the southeast of which an outflow
boundary serving as an effective front has led to a line of
convection extending out into the Gulf of Mexico. Along this
boundary, low-level convergence of an extremely favorable airmass
is being enhanced by at least modest isentropic ascent, and the
high-res guidance suggests this line will persist for several
hours with a slow translation to the east. As it does, convection
along it will likely train SW to NE on 10-15 kts of
boundary-parallel 0-6km mean flow with aligned Corfidi vectors
that are 5 kts or less. Within these cells, rain rates of 2"+/hr
or more are likely, and where this pushes onshore an additional
2-3" of rainfall is possible. The most robust amounts are likely
along the immediate coast southeast of Lake Charles, LA.

Although the heaviest rainfall is likely where this line advects
towards the coast, additional clusters of convection are likely
across the Upper Texas coast and into south-central Louisiana.
Here, convergent bands are also expected to produce rounds of
thunderstorms, in an environment that can still support 1-2"/hr
rain rates for the next several hours as progged by the HREF.
Flash flooding is most likely along the southwest coast of LA due
to recent rainfall and the expected heaviest rain rates, which is
reflected by the greatest HREF exceedance probabilities for 3-hr
FFG. However, anywhere training can occur with 2"/hr rainfall,
flash flooding is possible before instability and coverage are
forecast to wane late this evening.


Weiss

ATTN...WFO...HGX...JAN...LCH...LIX...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 31829251 31759193 31569148 31359113 30919086
30539079 30149101 29959134 29799172 29619221
29699285 29729324 29639379 29389438 29069489
28799537 28659565 28649598 28889608 29209581
29699554 30179528 30609505 31109458 31469416
31639368 31789306

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AWUS01 KWNH 011803
FFGMPD
NMZ000-AZZ000-020002-

Mesoscale Precipitation Discussion 0425
NWS Weather Prediction Center College Park MD
203 PM EDT Fri Jul 01 2022

Areas affected...much of Arizona, far western New Mexico

Concerning...Heavy rainfall...Flash flooding possible

Valid 011802Z - 020002Z

Summary...Monsoonal moisture continues to promote thunderstorm
development, with localized flash flooding possible through peak
heating hours.

Discussion...Insolation and related destabilization was resulting
in expanding thunderstorm coverage over the past hour across the
discussion area. The storms are in a steep-lapse-rate environment
(7-8C/km) through the low to mid-levels, with abundant moisture in
the H7-H5 layer contributing to 1000-2000 J/kg SBCAPE. 1.2-1.4
inch PW values also exist in the environment, which should
encourage rain rates approaching 1 inch/hr at times beneath
heavier convection. Additionally, very weak wind fields were
contributing to slow and erratic storm motions, which could
prolong rain rates locally as storm motions will likely be
governed by local cold-pool generation processes.

The 12Z HREF (which is consistent with ongoing development)
suggests that the greatest coverage of storms will exist along the
higher terrain initially (particularly in the White Mountains and
across adjacent areas of southeastern Arizona) before increasing
in coverage areawide through 00Z. Storms will mainly be diurnally
driven, with some lessening of coverage after sunset. Localized, terrain-favored areas and burn scars could promote flash flooding
in a few spots this afternoon.

Cook

ATTN...WFO...ABQ...EPZ...FGZ...PSR...TWC...VEF...

ATTN...RFC...CBRFC...WGRFC...NWC...

LAT...LON 36771172 36531065 35670962 35280866 34720810
33620839 32470853 31670858 31340895 31321021
31631144 31951205 32971225 34001263 34831330
35511339 36041315 36591254

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AWUS01 KWNH 022021
FFGMPD
COZ000-NMZ000-AZZ000-UTZ000-030218-

Mesoscale Precipitation Discussion 0434
NWS Weather Prediction Center College Park MD
420 PM EDT Sat Jul 02 2022

Areas affected...eastern Arizona, western New Mexico, much of
Colorado, and eastern Utah

Concerning...Heavy rainfall...Flash flooding possible

Valid 022018Z - 030218Z

Summary...Isolated to scattered convection continues to deepen in
tandem with strong insolation and monsoonal moisture. The storms
will pose a localized flash flood through at least sunset.

Discussion...Isolated to scattered convection continues to deepen
especially along higher terrain and ridgelines this afternoon.
The storms are in a typical monsoon pattern, with surface heating,
steepening lapse rates, and a layer of moisture at the 500-600mb
layer contributing to areas of 250-1000 J/kg SBCAPE - highest
across southwestern NM and southeastern Arizona where moisture
values are locally higher. Weak wind fields continue across the
region, which was contributing to slow and at times erratic storm
motions. Additionally, localized areas of 1+ inch/hr rainfall
rates were apparently via MRMS estimates, which are capable of
exceeding FFGs on a localized basis and causing excessive runoff
near terrain-favored areas and burn scars.

One mitigating factor for a more widespread flash flood risk is
the presence of fewer convective signals in models/CAMs compared
to prior afternoons across the discussion area. This is
consistent with slightly lower PW values and drier air aloft
especially across northern portions of the discussion area (i.e.,
Utah and Colorado). The lower convective coverage should result
in a more isolated flash flood risk, although this risk is
non-zero. As typical for the time of year, the risk should
decrease somewhat after 02Z or so in tandem with decreasing
insolation and low-level stabilization from surface cooling and
convective overturning.

Cook

ATTN...WFO...ABQ...BOU...EPZ...FGZ...GJT...PSR...PUB...SLC...
TWC...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON 40350840 40150686 39570579 38740537 37640496
36620489 35730537 34940610 34180668 33410672
32710713 32060813 31590819 31250836 31251101
31521186 32121153 32951107 33721117 34301167
34821219 35651198 36561124 37701059 38631018
39770954

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AWUS01 KWNH 030936
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-031535-

Mesoscale Precipitation Discussion 0436
NWS Weather Prediction Center College Park MD
535 AM EDT Sun Jul 03 2022

Areas affected...Southern AR...Northern LA...West-Central MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 030935Z - 031535Z

SUMMARY...A locally significant threat of very heavy rainfall will
exist this morning across parts of southern AR, northern LA and
possibly west-central MS as slow-moving showers and thunderstorms
develop and locally train over the same area. Areas of flash
flooding are expected.

DISCUSSION...GOES-16 Proxy Visible satellite imagery shows a
nearly stationary and long-lived MCV situated over the lower MS
Valley this morning, with the center of it over far southern AR.
The energy is somewhat stretched out west to east across the
region, but this system is expected to gradually be a driver this
morning of locally focused showers and thunderstorms with concerns
for extremely rainfall rates and areas of flash flooding.

The expectation going toward dawn and through the early to
mid-morning hours is for convection to initiate around the
southern and southwest periphery of the MCV as increasingly
confluent, and very moist/unstable low-level flow arrives from the
Arklatex region. Already the airmass pooled over northeast TX and
northwest LA is moderately unstable with MLCAPE values of 1500 to
2000+ j/kg. Meanwhile, PWs are high with values near 2.25 inches.
Facilitating the transport and pooling of this highly favorable
thermodynamic environment will be the proximity of a weak 850 mb
low over central AR which will support some of the stronger
low-level confluence setting up over far southern AR.

Given the tropical environment of the vertical column, the
rainfall processes this morning will be extremely efficient, and
capable of resulting in extreme rainfall rates that may exceed 3
inches/hour with the stronger convective cores.

Consecutive runs of the HRRR guidance and the 00Z HREF suite
suggest the potential for locally high-impact rainfall this
morning as the shower and thunderstorm activity develops within an
environment conducive for backbuilding and cell-training.

Rainfall totals going through 15Z (10AM CDT) of 4 to 6 inches are
generally expected, with isolated heavier amounts not out of the
question. The 00Z HREF does indicate some elevated probabilities
(locally over 50%) of seeing the 6-hour QPF exceed the 10-year
ARI, and there are even some low-end probabilities (20% to 30%) of
seeing the 100-year ARI exceeded. Far southern AR is the area of
greatest concern, but the threat of excessive rain will include
northern LA and possibly west-central MS. Given the set-up, areas
of flash flooding are likely, and some of it may potentially be
significant by later this morning.

Orrison

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 34389177 34339088 33869022 33159014 32579109
32389218 32459335 32719391 33079412 33479401
33889340 34199262

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AWUS01 KWNH 031817
FFGMPD
MTZ000-IDZ000-WAZ000-040000-

Mesoscale Precipitation Discussion 0438
NWS Weather Prediction Center College Park MD
216 PM EDT Sun Jul 03 2022

Areas affected...Northeast Washington and the Panhandle of Idaho

Concerning...Heavy rainfall...Flash flooding possible

Valid 031815Z - 040000Z

Summary...Showers and isolated thunderstorms will increase in
coverage across eastern Washington this aftn. As this activity
lifts northward, rain rates above 0.5"/hr are possible. This could
produce excessive runoff and flash flooding.

Discussion...The GOES-E WV imagery this aftn clearly indicates a
sprawling closed mid-level low centered over Washington. East of
the low, a plume of anomalous PW is surging northward into MT and
then wrapping cyclonically into WA, noted by an increase in the
LPW fields between 700-500mb and 500-300mb. While a dry slot is
obvious in the WV imagery moving over the Columbia Basin, PWs are
still measured by GPS to be 0.8-1.0 inches, above the 90th
percentile for the date at KOTX. Within this dry slot, a shortwave
is noted moving northward out of Oregon, and clearing in the
visible imagery is allowing for the rapid development of Cu/TCu
across the area as SBCAPE climbs to 500-1000 J/kg. Pronounced deep
layer ascent through mid and upper level diffluence/divergence,
PVA downstream of the shortwave, and increasing upslope flow on
low-level S/SE winds should lead to widespread convective coverage
through the aftn.

While activity so far has been limited due to modest instability,
the overlap of ascent within the increasingly favorable
environment suggests showers with isolated thunderstorms will
rapidly develop in the next few hours. This is echoed by the
simulated reflectivity from much of the available high-res
guidance. Rainfall rates within the blossoming convection could
reach 0.5"/hr or more as forecast by the UW 12km WRF, with low
probabilities for 1"/hr rainfall progged by the 12Z HREF. Mean
0-6km winds will point northward and range in speed from just
around 10 kts near the Cascades to 20 kts across the Idaho
Panhandle. While this suggests the potential for slower moving
storms near the low center, aligned propagation vectors indicate
the likelihood for some short duration training anywhere across
the region. Additionally, upslope flow into the Okanogan Highlands
or eastern Cascades could cause some storms to become tied to the
upwind side of terrain features, leading to nearly stationary net
movement. Where training, or this slowest motion, can occur,
rainfall could reach 1-2", with locally higher amounts exceeding
3" as forecast the 6-hr HREF probabilities.

Although 7-day rainfall has been scarce, 40cm soil moisture is
still above, to well above, normal according to NASA SPoRT. This
is likely due to excessive rainfall that occurred across WA in
early-mid June. These saturated soils have allowed FFG to remain
as low as 0.75-1"/3hrs, which has a greater than 60% chance of
exceedance according to the HREF. This heavy rainfall will likely
lead to excessive runoff in some areas, with instances of flash
flooding possible where training can occur across the most
sensitive terrain or atop any recent burn scars.

Weiss

ATTN...WFO...MSO...OTX...SEW...

ATTN...RFC...NWRFC...NWC...

LAT...LON 49241758 49171612 48851591 48551587 48161590
47891617 47801654 47731746 47651831 47631936
47692006 47932087 48202123 48622144 49092144
49172007

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AWUS01 KWNH 031852
FFGMPD
COZ000-NMZ000-AZZ000-UTZ000-040045-

Mesoscale Precipitation Discussion 0439
NWS Weather Prediction Center College Park MD
251 PM EDT Sun Jul 03 2022

Areas affected...Eastern AZ, Western NM, Southern CO

Concerning...Heavy rainfall...Flash flooding possible

Valid 031850Z - 040045Z

Summary...Showers and thunderstorms developing within the monsoon
surge will create rainfall rates of greater than 0.5"/hr this aftn
and evening. Training of these rain rates may produce 1-2" of
rainfall and isolated flash flooding.

Discussion...The GOES-E IR imagery this aftn depicts cooling cloud
tops embedded within a plume of high PWs coincident with the
monsoon flow. PWs within this plume are measured via GPS to be
0.75" to 1.2", highest near the AZ/Mexico border, and around 1.5
to 2 standard deviations above the climo mean. SBCAPE analyzed by
the SPC RAP has increased to more than 1000 J/kg across much of
the area, fueling a rapid increase in both coverage and intensity
of convection. This is reflected by the regional radar mosaic
which depicts scattered to widespread showers from far eastern AZ,
through much of western NM, and into southern CO, with
radar-estimated rain rates as high as 0.5-1"/hr.

The continued increase in instability combined with persistent
deep layer S/SW flow to advect higher PWs northward will maintain
favorable thermodynamics for heavy rain. Both the HREF and UA WRF
are forecasting scattered rain rates of greater than 0.5"/hr,
possibly locally reaching 1"/hr. At the same time, deep layer
ascent will likely increase through the evening through modest
upper diffluence in the RRQ of a distant jet streak combined with
subtle height falls as a longwave trough extending from a closed
low in the Pacific Northwest advects southeastward. This lift into
the favorable thermodynamics will likely also drive an increase in
coverage through peak heating, and the simulated reflectivity of
the high res suggests widespread showers and thunderstorms
developing.

Storm motions are expected to remain modest from the S/SW at 10-15
kts. This in itself could produce locally significant rainfall.
However, weak propagation vectors of around 5 kts aligned to the
mean wind indicate the likelihood for some training as well. This
could result in multiple rounds of convection through the evening,
which could produce 1-2" of rainfall in some areas. FFG in the
vicinity of the Four Corners is generally 2-3"/3 hrs, but there
exist pockets as low as 0.75"/3hrs due to recent excessive
rainfall, and the HREF forecasts a better than 20% chance of
exceedance atop the lowest FFG. However, these impressive rain
rates, especially where any training can occur, could lead to
rapid runoff even atop the drier soils. While flash flooding is
generally forecast to be isolated, it is most likely where any
training can occur across recent burn scars or the most sensitive
terrain features.


Weiss

ATTN...WFO...ABQ...BOU...EPZ...FGZ...GJT...PSR...PUB...TWC...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON 39070701 38680514 37950433 37380437 36860475
36540517 36040583 35750638 35190689 34280728
33580748 33140765 33000794 32900833 32900892
32930923 33070962 33261019 33521050 34011065
34741061 35511029 36260991 37130935 37730900
38630840 38850806

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AWUS01 KWNH 032135
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-040200-

Mesoscale Precipitation Discussion 0441
NWS Weather Prediction Center College Park MD
534 PM EDT Sun Jul 03 2022

Areas affected...southeastern Tennessee, southwestern North
Carolina, northern Georgia, upstate South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 032134Z - 040200Z

Summary...Slow-moving storms are posing a localized flash flood
risk across the southern Appalachians this afternoon. This threat
should persist through sunset.

Discussion...Loosely organized clusters of storms are located
along and south of a front extending along and just south of the Kentucky/Tennessee border region and adjacent areas of far
northwestern North Carolina. Along and south of this boundary, a
moist unstable pre-convective airmass (characterized by 1500-2500
J/kg SBCAPE and 1.8-2.0 inch PW values) were supporting continued
updrafts. Meanwhile, very weak shear profiles were supporting
slow southward movement and propagation along gust fronts. The
environment was supporting localized areas of 1-2.5 inch/hr
rainfall rates (based on MRMS). These cells were encouraging low
to moderate FLASH responses in a few locales this afternoon
despite relatively high FFGs (exceeding 2.5 inch/hr thresholds
except for on a localized basis).

The concern is that a few areas downstream of the slow-moving
clusters will experience a brief/localized flash flood threat this
evening. This will especially be the case if heavier rain rates
can materialize in more sensitive and more urbanized areas (i.e.,
Chattanooga, Charlotte, etc.). Storms should be primarily
diurnally driven, with a downtick in convective coverage expected
(based on models/CAMs) around 02Z or so.

Cook

ATTN...WFO...BMX...CAE...FFC...GSP...HUN...MRX...OHX...RAH...
RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON 36248447 36098284 36038121 36028027 35457992
34698031 33968145 33478301 33548455 34028553
34428586 35688645 35928578

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AWUS01 KWNH 061636
FFGMPD
WVZ000-OHZ000-INZ000-062230-

Mesoscale Precipitation Discussion 0458
NWS Weather Prediction Center College Park MD
1236 PM EDT Wed Jul 06 2022

Areas affected...Southeastern IN...Central and Southern
OH...Northwestern WV

Concerning...Heavy rainfall...Flash flooding possible

Valid 061634Z - 062230Z

SUMMARY...Storms to continue to train west to east across the
region, with increasing coverage during the afternoon. Locally
heavy rainfall is likely. Given the wet antecedent soil
conditions, flash flooding is possible.

DISCUSSION...Supported by a series of shortwaves, including a
well-defined wave moving east across Indiana, satellite and radar
show convection continuing to develop and train west to east along
a mesoscale boundary that currently extends from southeastern
Indiana to western Pennsylvania. Ample moisture remains in place,
with the latest mesoanalysis indicating PWs of 1.75-2 inches
across much of the highlighted area. MLCAPEs are generally in the
500-1500 J/kg, but are expected to increase with daytime heating
through the afternoon. Deep, persistent west-southwesterly flow
will likely tap the relatively deeper moisture upstream over the
mid Mississippi Valley (PWs at or above 2 inches) -- fortifying
the ample moisture already in place. These factors combined with
mean flow that is forecast to remain parallel to the boundary is
expected to support the threat for training storms and raise the
threat for heavy amounts. For the 6hr period ending 21Z, the 12Z
HREF shows high neighborhood probabilities (40km) for an inch or
more across much of the highlighted area, with high probabilities
for 2 inches or more centered over central Ohio. This includes
areas where the latest 3-hr FFG values are under inch. The HREF
also shows high probabilities for accumulated amounts exceeding
flash flood guidance values during the afternoon.

Pereira

ATTN...WFO...CLE...ILN...IND...IWX...PBZ...RLX...

ATTN...RFC...OHRFC...NWC...

LAT...LON 40618292 40228158 39568063 38908075 38698152
39158373 39198501 39318567 39678615 40088592
40368526 40558453

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AWUS01 KWNH 071654
FFGMPD
MNZ000-NEZ000-SDZ000-072253-

Mesoscale Precipitation Discussion 0462
NWS Weather Prediction Center College Park MD
1254 PM EDT Thu Jul 07 2022

Areas affected...Central to Eastern SD

Concerning...Heavy rainfall...Flash flooding possible

Valid 071653Z - 072253Z

Summary...Slow moving thunderstorms producing rain rates up to
2"/hr at times this afternoon may cause localized flash flooding.

Discussion...As of 17Z, radar imagery showed a MCS over
north-central SD that is moving slowly to the east/southeast. This
activity is working on the periphery of strong upper ridge
centered over the southern U.S. and a subtle speed max at 250 mb
helping to provide favorable forcing for ascent. The environment
across the region is characterized by more than sufficient
moisture with the blended TPW product showing values exceeding
1.7" (12Z ABR sounding of 1.74" was near daily max record) that
has pooled on the warm side of a frontal boundary draped to the
north and plenty of SBCAPE in place thanks to rich low level
moisture (Tds in low 70s) and increasing insolation.

Hi-res guidance suggest with peak heating and convective
temperatures being reached, the current MCS should sustain itself
as it moves east/southeast while additional convection is expected
to blossom ahead of it along residual outflow boundaries from
earlier convection. The high moisture and instability fields
should sustain rain rates up to 2"/hr rain rates at times. Mean
flow under 10 kts will keep storm motions relatively slow.

The latest HREF probabilities show a moderate signal for totals
isolated totals in excess of 3" through 23Z (40-50 percent probs)
and a notable signal for the precip to exceed the 3-hr and 6-hr
flash flood guidance. Over the last 2 weeks, portions of the
outlook area have seen much above normal precipitation (200-400
percent of normal) and as a result, the latest NASA SPoRT soil
moisture percentiles in the top 40 cm layer are between 60-70
percent saturation. The combination of the intense, efficient rain
producing thunderstorms over some sensitive soil conditions could
lead to isolated/scattered instances of flash flooding through
this afternoon.

Taylor


ATTN...WFO...ABR...FSD...LBF...UNR...

ATTN...RFC...MBRFC...NCRFC...NWC...

LAT...LON 45839663 44609665 43649719 43279884 42870113
43150171 43700123 44230039 44659976 45799890


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AWUS01 KWNH 081441
FFGMPD
WVZ000-OHZ000-KYZ000-INZ000-082000-

Mesoscale Precipitation Discussion 0466
NWS Weather Prediction Center College Park MD
1041 AM EDT Fri Jul 08 2022

Areas affected...Southeast IND..Southwest OH...Northern &
Northeast KY...Far Western WV

Concerning...Heavy rainfall...Flash flooding possible

Valid 081440Z - 082000Z

SUMMARY...Successive arcs of thunderstorms moving toward
hydrologically sensitive areas with increasing instability/growth
potential toward early afternoon and continued scattered possible
flash flooding.

DISCUSSION...Diurnal lull in convective intensity remains fairly
robust with multiple lines/arcs of thunderstorms progressing
eastward along/south of the warm front across the Central Ohio
River Valley. Goes-Visible imagery denotes an area of
clearing/broken stratus across Northern KY/Southwest OH starting
to burn off across W WV, generally south of the warm front that
extends from MWO to PMH to CRW and south.

Upstream leading but weakening outflow boundary is crossing into
KY while upstream much stronger reinvigorating convection across
SW IND at the lead edge of stronger moisture convergence
along/ahead of the MCV still feeding off weak to modest ~1000 J/kg
instability, while advecting highly saturated deep moisture
profile with total PWat value at/near daily record values of
2.25+". As such, instantaneous rates are fairly extreme but some
weak cold pool/height-falls have reduced hourly totals into the
1.5-2" range. In the short-term, this may not result in all but
urban or highly sensitive basins to result in flash flooding given
recently dry ground conditions/localized higher FFG values across
S IND/north-central KY. However, aforementioned clearing is
supporting rising surface temps into the low 80s and supporting
1500 J/kg SBCAPEs in the next hour or so. This will allow for
further cell growth/intensification as the cells also progress
into NE KY/SW OH where recent heavy rainfall has reduced soil
capacity, though rates should also increase to 2"/hr again
supporting higher potential for increased coverage from isolated
to scattered flash flooding potential. Greatest uncertainty is
forward progression which is continues to be under-forecast by
Hi-Res CAMs but still supports localized 1hr FFG value exceedance
suggesting possible flash flooding through early afternoon.

Subtle but stronger capping along the southern/upstream flanks of
bands of thunderstorms should limit coverage further south through
early afternoon, but there is growing signal for increasing
convective development along the outflow boundaries toward the
south in the 20-21z time frame...so will continue to monitor this
area closely for subsequent MPD for early initiation.

Gallina

ATTN...WFO...ILN...IND...JKL...LMK...RLX...

ATTN...RFC...OHRFC...NWC...

LAT...LON 39418546 39188364 38888221 38088201 37518250
37578425 37998633 38658701 39298652

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AWUS01 KWNH 091900
FFGMPD
VAZ000-NCZ000-100100-

Mesoscale Precipitation Discussion 0471
NWS Weather Prediction Center College Park MD
259 PM EDT Sat Jul 09 2022

Areas affected...Southern VA...Northern & Norteastern NC...

Concerning...Heavy rainfall...Flash flooding possible

Valid 091900Z - 100100Z

SUMMARY...Slow moving highly efficient thunderstorms capable of
2-2.5"/hr and potential cell mergers/back-building pose possible
flash flooding conditions through the evening hours.

DISCUSSION...Very moist and increasingly unstable environment
exists along and south of a slow sagging frontal zone extending
across S VA back to the Central Appalachians. East of the higher
terrain in NW NC, Tds have increased to low to mid-70s with
isolated higher values; clear skies has allowed for Temps to rise
into the mid to upper 80s with 90s along and east of I-95. A
long-lived complex of stronger thunderstorms has supported
southward push of the cold front near Norfolk, VA nearing NE NC
with Cu streamers indicating solid confluence toward the upwind
edge of the complex suggesting the potential for upstream development/back-building with any increased isallobaric enhanced
convergence over the next few hours.

Concurrently, upstream a subtle 5H shortwave is nearing the apex
of the Central Appalachians providing weak but sufficient DPVA
forcing along the Blue Ridge. Recent observation from
thunderstorms near Rich Hill, NC denoted that increased available
deep moisture with TPW up/over 1.8-2" and up-slope convergence can
support extreme short-term rates with 1.25" in 30 minutes but .5"
measured in 5 minutes. While the shortwave is weak, it is
supported by 30-35kts of 5H flow enhancing effective bulk shear to
similar values supporting increased organization to thunderstorms
greater than up/down pulse convection as the forcing presses
eastward along the VA/NC boarder in the coming hours. RAP
analysis/forecast also suggest the general confluence along/ahead
of the sagging cold front will enhance moisture further toward 2"+
allowing for 2-2.5"/hr rates as convection reaches peak intensity
with peak heating toward 21-23z.

Hi-Res CAMS appear to have a good agreement to this evolution but
appear to running slow to the current trends with the HRRR a bit
south compared to the ARW/ARW2, still all generally place a
greater risk along the VA/NC boarder toward the I-40 corridor,
with back-building from the east increasing potential for cell
mergers perhaps in proximity to larger urban centers of
Raleigh-Durham and Greensboro with localized 2-4" totals dotted
along the W-E axis through 01z. While the central Piedmont has
higher FFG values, the potential for sub-hourly totals over 2" may
supersede and with limited time for infiltration could increase
overall runoff and possible flash flooding.

Gallina

ATTN...WFO...AKQ...GSP...MHX...RAH...RNK...

ATTN...RFC...OHRFC...SERFC...NWC...

LAT...LON 37168006 36827870 36557769 36517596 35597581
35017650 35147781 35417922 35748043 36178113
36748070
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AWUS01 KWNH 092209
FFGMPD
ALZ000-MSZ000-100400-

Mesoscale Precipitation Discussion 0472
NWS Weather Prediction Center College Park MD
608 PM EDT Sat Jul 09 2022

Areas affected...Eastern Mississippi...Central Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 092210Z - 100400Z

SUMMARY...Strong thunderstorms expanding into larger complex will
slowly move with highly efficient rainfall production (2.5"/hr
rates) posing scattered flash flooding potential through early
overnight hours.

DISCUSSION...GOES-E WV suite denotes a decaying closed low along
the northeastern edge of a dominant synoptic ridge anchored over
the Southern Plains with a weak positive tilt axis extending from
the Lower Ohio Valley back across E TN/AR. CIRA LPW denotes this
as an enhanced ribbon of 7-3H moisture that in combination with
sfc Tds in the 75-80F range across N MS result in 2-2.3" total
PWats across N MS. At the surface a low near TUP with a weak
surface boundary extending back into SW AR. While winds are
weak(er), there has been sufficient convergence along the frontal
boundary along with temps near convective temperature to support
convective initiation across much of the length of the boundary
from AR to N AL. In the short-term, cells may be less efficient
but also have greater potential for mergers or repeating given a
secondary line developed north and isolated cells along/ahead of
the front northeast of Birmingham. These short-term mergers may
result in isolated flash flooding given shear sub-hourly rates
limiting infiltration into the drier soils across N AL/N MS
(relative to central/southern).

Additionally, deep layered flow is generally weak (15-20kts) and
parallel to the boundary; however, with a fairly high dewpoint
depression propagation will likely be contingent on cold pool
generation and generally southward. Given the Tdd is greater west
than east as well as steering flow being along the NE side of the
500-1000 thickness ridge that bisects MS/AL from west to east,
should support slower southward propagation along the eastern
periphery of the convective line, allowing for localized hourly
totals of 2-2.5" especially as the complex drops into the
thickness ridge toward 00z...though much of that rain could fall
in less than 30 minutes given the strength of the moisture flux
into the cloud is driven by the convergence at the leading edge of
the cold pool. Back-sheared moderate anvil precipitation could
help with localized pockets up to 3.5" for totals.

Hi-Res CAMs have been fairly consistent with this evolution
through the evening hours with 18z HREF peak probabilities of
2"/hr over 40% from Perry to Coosa between 02-03z and neighborhood
probability of 3" generally around 45-50% across central AL. As
such, flash flooding is considered possible.

Gallina

ATTN...WFO...BMX...HUN...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34448705 34088568 33388539 32298561 31688708
31898852 32618924 33798935 34258840

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AWUS01 KWNH 101603
FFGMPD
VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-102200-

Mesoscale Precipitation Discussion 0477
NWS Weather Prediction Center College Park MD
1201 PM EDT Sun Jul 10 2022

Areas affected...Eastern SC...Central NC

Concerning...Heavy rainfall...Flash flooding possible

Valid 101600Z - 102200Z

Summary...Numerous showers and storms are expected to persist
going into the afternoon hours from the southern Appalachians to
the coast. Some instances of flash flooding are possible with
slow moving cells and for areas that have multiple rounds of heavy
convection through 6 pm local time.

Discussion...Regional Doppler radars continue to show a gradual
increase in the coverage and intensity of convection across the
outlook area, along with an increase in cooling cloud tops per
recent GOES-16 infrared satellite imagery. This is occuring in
the general vicinity of a stalled frontal boundary across central
South Carolina.

There are two main areas of concern, with the first from the Sand
Hills of central South Carolina to the Low Country. A complex of
slow moving convection with a deep warm cloud layer and high
precipitation efficiency could easily produce rainfall rates on
the order of 1.5 to 2.5 inches per hour with the most persistent
cells. This is expected to expand in coverage and reach eastern
portions of the state and into southeast North Carolina, generally
after 3 pm local time. This will be more problematic for those
areas that have received significant rainfall over the past few
days.

The second area of concern is across the higher terrain of western
North Carolina and far eastern Tennessee. Although the overall
rainfall totals are expected to be less compared to locations
farther east, flash flood guidance is considerably lower and HREF
neighborhood exceedance probabilities of this parameter are on the
order of 50+ percent for 3 hourly QPF. The cells that develop
will likely be slow moving owing to very weak low-mid level
steering flow, and flash flooding will be possible with the
strongest storms.

Hamrick

ATTN...WFO...CAE...CHS...FFC...GSP...ILM...MRX...RAH...RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON 36658227 36658172 36408136 35888112 35418062
35067980 34887907 34727838 34327773 33837790
33787844 33527884 33157911 32717979 32698051
33188103 33848142 34358199 34548289 34428415
34798456 35278453 35698403 36028348 36298296
36568263

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AWUS01 KWNH 111831
FFGMPD
COZ000-NMZ000-120030-

Mesoscale Precipitation Discussion 0481
NWS Weather Prediction Center College Park MD
230 PM EDT Mon Jul 11 2022

Areas affected...Southern Colorado...Northern New Mexico

Concerning...Heavy rainfall...Flash flooding possible

Valid 111830Z - 120030Z

SUMMARY...Approaching cold front providing focused lift along the
front and introducing additional low-mid level moisture into the
Central Rockies will help fuel monsoon t-storms this afternoon.
Hourly rainfall rates >1"/hr could lead to areas of flash flooding.

DISCUSSION...A cold front racing south through the central High
Plains is ushering in higher RH at low-mid levels in its wake,
while also allowing for NNE winds behind it to upslope into the
Front Range of the Colorado Rockies. Water Vapor imagery has also
identified a series of gravity waves tracking into central
Colorado and northern New Mexico. This gravity wave can also help
initiate convection sooner over parts of the region, especially in
higher terrain where a field of towering cumulus clouds continue
to build. Meanwhile, a nearby vortmax to the southwest will aid in
keeping weak steering flow winds in place and act as a weak source
of lift over the Four Corner region.

In terms of parameters, PWs will range up to 0.75" and MUCAPE
according to the latest RAP is expected to range between 500-1,000
J/kg in late afternoon and early evening. The primary issue comes
from quasi-stationary storm motions, which could support hourly
rainfall rates >1"/hr. The 12Z HREF does show as much as a 40-45%
chance for >1"/hr rainfall rates beyond 20Z this afternoon with up
to a 25% chance of 1-hr FFG exceedance. Soil moisture percentiles,
according to NASA SPoRT-LIS, are >98% in parts of the region with
burn scars most susceptible to possible flash flooding and rapid
runoff. Given the saturated antecedent soil moisture conditions,
along with the strong convection set to develop this afternoon
along the front and atop the higher terrain, there could be areas
of flash flooding this afternoon and into the early evening hours.

Mullinax

ATTN...WFO...ABQ...BOU...GJT...PUB...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON 39870531 39080486 38120449 37410342 36630314
36150406 35580504 35220556 34640645 35280664
35130739 35410780 35920750 36510741 37060795
37440824 38020775 38860741 39220693 39740605


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AWUS01 KWNH 121723
FFGMPD
COZ000-NMZ000-122300-

Mesoscale Precipitation Discussion 0486
NWS Weather Prediction Center College Park MD
123 PM EDT Tue Jul 12 2022

Areas affected...Southern Colorado...Northern New Mexico

Concerning...Heavy rainfall...Flash flooding possible

Valid 121720Z - 122300Z

SUMMARY...Slow moving storms containing hourly rainfall rates

1"/hr may cause areas of flash flooding, especially in areas with

overly saturated soils or near burn scars.

DISCUSSION...A lingering pool of 700-300mb moisture remains
entrenched atop the southern and central Rockies. 850mb flow over
the TX/OK Panhandles remain out of the east ushering low level
moisture into the region while also aiding in upslope flow into
the Front Range of the Rockies. Steering flow winds are strongest
in the central Colorado Rockies (10-15 kts) but the lighter winds
(<10 kts) are located in southern Colorado and northern New
Mexico. Latest RAP forecast show generally 500-1,000 J/kg of
MUCAPE will be available this afternoon with totals >1,000 J/kg
possible in the San Juan and Sangre De Cristo ranges. PWs >0.75"
will be positioned in southern Colorado and northern New Mexico
with the best odds of >1.00" PWs in the High Plains of northeast
New Mexico.

The 12Z HREF does contain 30-35% probabilities of rainfall rates

1"/hr at times, which would challenge 1-hr FFGs in parts of the

southern and central Rockies. Additional cells may develop as
storms drop outflow boundaries and trigger other areas of storms
into the early evening hours, perhaps as far east as the High
Plains where storms may fire along a nearby surface trough. Much
of the higher elevations of south-central Colorado and northern
New Mexico continue to sport overly saturated soils. Some
locations, according to NASA SPoRT-LIS, show 0-40 cm soil moisture
percentiles >98%. It is in these locations, along with neighboring
burn scars, where flash flooding has the best odds of occurring.

Mullinax

ATTN...WFO...ABQ...BOU...GJT...PUB...

ATTN...RFC...ABRFC...CBRFC...MBRFC...WGRFC...NWC...

LAT...LON 39430663 39400534 37980388 36260397 34620625
35150761 36960748 37860852 38720733

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AWUS01 KWNH 121833
FFGMPD
AZZ000-122300-

Mesoscale Precipitation Discussion 0487
NWS Weather Prediction Center College Park MD
232 PM EDT Tue Jul 12 2022

Areas affected...Mogollon Rim to Gila Mtns of Arizona....

Concerning...Heavy rainfall...Flash flooding possible

Valid 121830Z - 122300Z

SUMMARY...Monsoon thunderstorms capable of 1-1.5"/hr totals pose
isolated flash flooding concern over the next few hours.

DISCUSSION...RAP and mesoscale observational analysis depicts a
subtle 5H shortwave feature rotating westward along the southern
periphery of the larger scale low near Greenlee to N Graham
county. CIRA LPW denotes a tight gradient along the eastern side
of the Mogollon Rim into the White/Gila Mtns of E Arizona with
85-7H around .6 and similar .6 values in the 7-5H layer. Flow is
very weak, but near cloud base height there is southerly flow
upsloping across eastern Arizona with 10-15kts providing ample
moisture flux to increasingly destabilized area per RAP
instability analysis. As such, a few cells have developed over S
Apache county, likely to expanding westward as the 5H wave lifts
that way. Additionally, upper level apex of the 3-25H ridge is
centered around 112W with increased diffluence across the central
to eastern Rim, providing some further aid for updraft strength.

While shear/flow is limited cells should produce 1-1.5"/hr rates
and similar totals given likely one, maybe two cycle updrafts
before propagating along outflow boundaries. Cells could anchor a
bit along the terrain due to upslope flow for the initial few
hours aiding possible localized enhanced rainfall totals, but
given fairly good saturation of profiles...isolated flash flooding
is considered possible through late afternoon into evening.

Gallina

ATTN...WFO...FGZ...PSR...TWC...

ATTN...RFC...CBRFC...NWC...

LAT...LON 35541181 34881072 34660970 34490930 34110907
33340916 33120973 33721125 34371212 35261254


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AWUS01 KWNH 131814
FFGMPD
VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-140000-

Mesoscale Precipitation Discussion 0493
NWS Weather Prediction Center College Park MD
213 PM EDT Wed Jul 13 2022

Areas affected...Northern GA...Western SC...Central NC...Southeast
VA

Concerning...Heavy rainfall...Flash flooding possible

Valid 131810Z - 140000Z

SUMMARY...Thunderstorms emerging out of the southern Appalachians
to advance east into an increasingly unstable and moisture-rich
environment. Excessive Rainfall rates >2"/hr could potentially
lead to flash flooding.

DISCUSSION...Agitated cumulus towers are growing into mature
thunderstorms along the southern Appalachians and along the
surface trough early this afternoon. Surface based heating is
making the atmosphere increasingly unstable with SBCAPE forecast
to reach ~3,000 J/kg later this afternoon. In terms of moisture
content, PWs over the Appalachians are as high as 1.5", but in
western SC and the NC Piedmont, PWs range between 1.75-2.00". The
latest RAP forecast suggests PWs could surpass 2.0" in these areas
later this afternoon and extend as far north as southeast VA.
These parameters support the potential for excessive rainfall
rates >2"/hr. The latest 12Z HREF shows 3-hr QPF > 3-hr FFG
probabilities as high as 40% in parts of the the NC Piedmont. In
southeast VA, 12Z HREF shows probabilities up to 20% for rainfall
rates >2"/hr.

Antecedent soil conditions remain quite saturated throughout much
of the highlighted region. NASA SPoRT-LIS indicates 0-40cm soil
moisture percentiles are as high as 90-95% in portions of central
NC and western SC. In addition, the last 7 days have featured
heavy rainfall totals across much of the Southeast, including
upwards of 300-400% of normal from northeast GA to central NC.
Given the conducive environment and exceptionally saturated soils
in the Southeast, thunderstorms could produce areas of flash
flooding later this afternoon and into the early evening hours.
Urbanized locations and poor drainage areas are most at risk.

Mullinax

ATTN...WFO...AKQ...CAE...FFC...GSP...ILM...MRX...RAH...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 37657758 37017613 36177739 35337855 35007920
34528056 33978174 33408291 33618370 34148502
34698460 35408369 36288230 36658109 36927943


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AWUS01 KWNH 141701
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-142300-

Mesoscale Precipitation Discussion 0498
NWS Weather Prediction Center College Park MD
101 PM EDT Thu Jul 14 2022

Areas affected...Central Gulf Coast

Concerning...Heavy rainfall...Flash flooding possible

Valid 141700Z - 142300Z

SUMMARY...Slow moving thunderstorms due to a combination of a
remnant MCV and diurnally driven surface based heating could
result in flash flooding. Max rainfall rates could top out as high
as 3"/hr in the more intense cells.

DISCUSSION...GOES-16 water vapor imagery showed a remnant MCV
swirling over central Louisiana as of midday, a feature associated
with convection that occurred last night. Closer to this feature,
say roughly from New Orleans on west towards west-central
Louisiana, mean wind speeds are much lighter. Mean winds in the
850-300mb layer will be closer to 10 knots or so near New Orleans,
but Baton Rouge and points north and west into central Louisiana
and southwest Mississippi are forecast to see steering flow winds
<5 knots this afternoon according to the latest RAP.
Thermodynamically, surface based heating will continue to further
destabilize Louisiana with MLCAPE eventually surpassing 2,000
J/kg. PWs will also remain in the 2.0-2.2" range and warm cloud
layers are as deep as 13,000' AGL. Hi-res guidance shows typical
garden-variety shower and thunderstorms throughout the region, but
the MCV is the wildcard. Should it act as a more focused source of
vertical ascent in the column than modeled, there is a chance for
organized upscale convective growth in Louisiana and southern
Mississippi. The 12Z HREF does show 1-hr QPF > 1-hr FFG
probabilities as high as 15-20% at varying times this afternoon,
so there is at least a chance some of these storms could generate
rainfall rates as high as 3"/hr, but these heavier totals would be
localized. Flash flooding is possible given the slow storm motions
and potential for torrential downpours. Urbanized areas and
typical lower lying, poor drainage areas most at risk.

Farther east, from southern Mississippi/Alabama to the far
northwest Florida Panhandle, spotty showers and thunderstorms have
begun flaring up across the region. Similar atmospheric profiles,
including MLCAPE and PW parameters, are in place but with slightly
faster WSW steering flow aloft (10-15 kts between 18-00Z). Still,
12Z HREF probabilities for >2"/hr rainfall rates range between
30-40% in these areas this afternoon. Parts of the central Gulf
Coast remain overly saturated according to NASA SPoRT-LIS, which
indicates >90% 0-40cm soil saturation from northeast of Gulfport
on east to Mobile Bay and east of Pensacola. Some locations a
little farther inland (north of I-10) are not as saturated but
have also received rainfall over the past 7 days that are 200-300%
of normal. With antecedent soil moisture on the higher side and
the potential for 2-3"/hr rainfall rates, there is a chance for
flash flooding despite the slightly faster storm motions compared
to their neighbors in central and eastern Louisiana.

Mullinax

ATTN...WFO...JAN...LCH...LIX...MOB...SHV...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 31808770 31418582 30258577 29788837 28938940
29359192 29919284 30989306 31549246 31759155
31639034 31708905

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AWUS01 KWNH 141746
FFGMPD
AZZ000-UTZ000-NVZ000-142330-

Mesoscale Precipitation Discussion 0499
NWS Weather Prediction Center College Park MD
145 PM EDT Thu Jul 14 2022

Areas affected...Southern Utah...Northern Arizona

Concerning...Heavy rainfall...Flash flooding possible

Valid 141745Z - 142330Z

SUMMARY...Vigorous monsoonal thunderstorms to produce locally
intense rainfall rates. Burn scars, slot canyons, and areas with
overly saturated antecedent soil moisture conditions are most
vulnerable to possible flash flooding.

DISCUSSION...GOES-16 water vapor imagery showed a 500mb vort max
tracking NNW out of the northern Gulf of California with an influx
of 850-700mb moisture surging north up the Lower Colorado River
Valley and into the Great Basin. PWs as high as 1.8" were
identified in parts of the Lower Colorado River Valley north of
Yuma but a larger swath of 1.0"+ PWs was over the Mogollon Rim and
on north into central Utah. Visible and IR satellite imagery shows
cumulonimbus towers blossoming over the area with GLM also
identifying lightning strikes becoming more numerous.

Storm motions within the mean 700-300mb flow will remain <10 kts
while anomalously high PWs engulf the highlighted region. Most PWs
in the highlighted region are above the 90th percentile from
18-00Z with the GFS even identifying some areas above the 95th
percentile. SBCAPE is also quickly rising to 500-1,000 J/kg,
further providing support for strong thunderstorms capable of
producing excessive rainfall rates. The 12Z HREF gave the higher
elevations of the Mogollon Rim the highest probabilities for

1"/hr rainfall rates, topping out as high as 40-50% in some cases

this afternoon. Parts of north-central Arizona are also featuring
soil moisture percentiles >98% in some cases. The potential for
hourly rainfall rates >1"/hr extend as far west as southeast
Nevada and as far north as central Utah. Slot canyons, burn scars,
rugged terrain, and overly saturated soils are where flash
flooding potential is highest with rapid water rises in gulleys
possible.

Mullinax

ATTN...WFO...FGZ...SLC...VEF...

ATTN...RFC...CBRFC...NWC...

LAT...LON 40371214 40261143 39551049 38451072 37541133
36131144 34841071 34311102 34801205 35481386
36191451 37001460 38131414 39081349 39841300


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AWUS01 KWNH 161205
FFGMPD
MNZ000-SDZ000-NDZ000-161700-

Mesoscale Precipitation Discussion 0511
NWS Weather Prediction Center College Park MD
805 AM EDT Sat Jul 16 2022

Areas affected...Eastern ND...Western MN...Northeast SD

Concerning...Heavy rainfall...Flash flooding possible

Valid 161200Z - 161700Z

SUMMARY...Mature MCS tracking south and east into moist and
unstable environment may lead to rainfall rates that result in
localized flash flooding.

DISCUSSION...A mature MCS continues to track ESE towards the Red
River Valley of the North this morning. Most rainfall rates have
been manageable for soils in the area, but there was one
quasi-stationary cell that led to some elevated FLASH CREST max
unit stream flow response south of Belcourt, ND. A surface trough
located west of Fargo and Grand Forks was oriented NW to SE
towards the ND/SD border and 850mb inflow was still ~20-30 kts.
Sufficient MUCAPE is expected to remain in place throughout the
morning downwind of the approaching MCS, with values ranging
between 1,000-2,000 J/kg. PWs are between 1.3-1.6", with the
higher values closer to the MCS. These PWs are close to the 90th
climatological percentile for much of central ND.

The latest HRRR is showing the MCS maintaining a steady forward
motion, but there are a couple items of note. The first is the
aforementioned surface trough, as the HRRR is suggesting
additional convective development along the trough over the next
couple hours. This is also being picked up by the 06Z HREF which
shows 1-hr QPF > 1-hr FFG probabilities as high as 30% just south
of Fargo between 15-18Z. The second is a gravity wave being picked
up by KMBX radar as it propagates south towards southern ND. This
could not only act to trigger additional storms closer to I-90
between Fargo and Bismarck, but area averaged soundings show
upshear Corfidi vectors as weak as 10-15 kts where the surface
trough is positioned.

Should convection manifest itself along the surface trough or on
the southwest flank of the MCS, backbuilding of developing cells
could occur. Low level inflow will lessen in intensity this
morning, but enough SW flow at low level intersecting the surface
trough could still be enough to maintain potent thunderstorms in
the area through late morning. 1-hr FFGs are as low as 1" in parts
of the Red River Valley, and they are 1.0-1.5" for 3-hr FFGs near
the Fargo area. With favorable thermodynamic profiles and
sufficient moisture content aloft, the potential for back building
cells could lead to localized flash flooding in low lying, poor
drainage, urbanized areas.

Mullinax

ATTN...WFO...ABR...BIS...FGF...MPX...

ATTN...RFC...MBRFC...NCRFC...NWC...

LAT...LON 49039842 48929647 48139568 46809570 45229646
45239792 46830031 47060063 47670189 48140197
48510173 48750093 48939966

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AWUS01 KWNH 171956
FFGMPD
MDZ000-VAZ000-NCZ000-DCZ000-WVZ000-TNZ000-180100-

Mesoscale Precipitation Discussion 0521
NWS Weather Prediction Center College Park MD
356 PM EDT Sun Jul 17 2022

Areas affected...Western VA...Northwest NC...Far Northeast
TN...DC...Central & Western MD...

Concerning...Heavy rainfall...Flash flooding possible

Valid 172000Z - 180100Z

SUMMARY...Slow moving, highly efficient rainfall producing
thunderstorms with potential for cell mergers and tracking through
areas of saturated grounds present scattered flash flooding
possible through the evening hours.

DISCUSSION...GOES-E WV suite depicts a broadening synoptic trof
with solid divergence pattern noted aloft with banded, highly
anti-cyclonically curved cirrus. The area of concern resides
along the outer periphery of the cirrus bands to support filtered
insolation across very moist low level environment. Surface Tds
in the low 70s in the Piedmont/eastern slopes of the Appalchains
and mid to upper 60s in the higher terrain have aided the temps to
near 90 and 85 respectively resulting in a broad area of
unstablility across the region. MLCAPEs of 2000-2500 are
expected.

Mid-level outer band/exit of 5H jet is providing an arc of
increased vorticity to rotate eastward providing large scale
ascent and low level pressure/wind response. Weak upslope flow
has been sufficient for deep moisture convergence to develop
stronger convection. Updrafts are broader and more numerous
further north toward N VA due to higher bulk shear values to
promote greater organization; though extend the length of the
vorticity strip into eastern slopes of NC Applachians. Cells
further south have reduced forcing, cell motions will be a bit
more limited to allow for greater duration and similar capability
of high rainfall rates. Total PWats of 1.7-2" (depending on
elevation mainly than the airmass itself) along with the flux will
support locally 2"/hr rates with a bulk of that coming in less
than 30 minutes. Propagation will occur along outflow boundaries,
including toward the west and the approaching height-falls, with
greatest potential for increase in coverage toward N VA/DC metro
given slightly higher lingering instability (up to 2500 J/kg).
Regardless, flash flooding is considered possible through the
length, with greatest probablity across N VA into central MD where
recent heavy rains have saturated the grounds with 300-500% of
normal reducing FFG values generally below expected hourly rates
(<2") and 3hr totals (<3").

Gallina

ATTN...WFO...AKQ...GSP...LWX...MRX...PBZ...RAH...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 39657797 39567688 39097651 38167733 37067900
36308010 35718129 35478246 36168334 36978274
37578178 38588023 39577919

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AWUS01 KWNH 172147
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-180300-

Mesoscale Precipitation Discussion 0523
NWS Weather Prediction Center College Park MD
546 PM EDT Sun Jul 17 2022

Areas affected...Lower Ohio Valley into Southern MO/Northern AR...

Concerning...Heavy rainfall...Flash flooding possible

Valid 172145Z - 180300Z

SUMMARY...Narrow streaks of enhanced rainfall totals (2-3.5") with
intense sub-hourly bursts along ahead of deep-layer trof/cold
front pose isolated flash flooding concerns

DISCUSSION...Broad synoptic trof across Lower Lake Michigan has
strong shortwave lobes rotating along/through presenting as an
elongated trof within GOES-WV back across the Bootheel of MO and
Arkansas. The current amplifying vort appears to be pivoting
across central IND with effective confluent WAA wing extending
across Central OH with effective cold front wing back SW. Strong
upstream 90 kt jet over MN is helping to dig shortwave over IA/WI
with 70 kt jet streak amplifying over N IND presenting highly
favorable right entrance ascent dynamics across the length of the
Lower Ohio River Valley this afternoon into late evening.
Moisture stream though the Mississippi and Southern Plains becomes
highly confluent and increased deep moisture source to over 2.25"
total PWats in the Valley. With the strong synoptic forcing,
cloud cover/debris has limited insolation, limiting overall
convective potential, with exception to the edges of synoptic
influence, in S MO/N AR and portion of W KY where instability
increased to 2500-3000 J/kg, along the front.

Still, limited instability (500-1000) along ahead of the cold
front/5H shear axis in S IND/S IL will support some strong
thunderstorm updrafts along maximized convergence near/along the
front. These cells will be capable of short intense burst of
highly efficient warm cloud processes with HRRR 15-min
rates/totals of 1.25". Given the high stream-wise shear within
the mid-levels, small vorticity centers will aid localized
convergence and support narrow lines of updrafts capable of
short-term training and streaks of 2-3.5" totals in 2-3hr periods
resulting in possible localized flash flooding.

A delicate balance is at play, where further north and east along
the axis, instability is less, but forcing is stronger with
potential for greater duration but lesser rates. Further south
and west, higher instability will support higher rainfall
production, but with faster cell motions may limit duration, as
well as drier ground conditions/higher FFG. As such flash flooding
is considered possible throughout the length of the upper level
trof, but increases further northeast along the axis.

Gallina

ATTN...WFO...ILN...ILX...IND...LMK...LSX...LZK...MEG...PAH...
SGF...

ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON 40278526 39378487 37928554 36428865 35729011
35819158 37029271 38249243 38499065 38858875
39518670

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AWUS01 KWNH 181832
FFGMPD
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-190000-

Mesoscale Precipitation Discussion 0528
NWS Weather Prediction Center College Park MD
231 PM EDT Mon Jul 18 2022

Areas affected...CT...Southern NY...NJ...Eastern PA...Central
MD...Northern& West-Central VA

Concerning...Heavy rainfall...Flash flooding possible

Valid 181830Z - 190000Z

SUMMARY...Highly efficient rainfall production with some
short-term repeating/training poses possible flash flooding
concerns, particularly across the larger urban corridor and
saturated soil conditions across MD/N VA.

DISCUSSION...GOES-E WV suite depicts elongated upper trof with
deepening lead shortwave over SE Canada, though important smaller
vorticies along the axis from W NY to KY. Deeper moisture in the
warm conveyor belt appears to have translated over the
Appalachians and melded with surface/low level moisture in place
to allow for highly anomalous total PWat values of 2"+ increasing
to near 2.2" as further mid to upper level flow saturates the
column. Strong insolation has also allow for these saturated
profiles to produce impressive narrow-skinny 2000-2500 J/kg MLCAPE
values along the length of the area of concern.

While the front is still well west of the area, there is
sufficient boundary layer confluence to support convective
initiation as Visible imagery indicates a few clusters north of
NYC and along the Blue Ridge, but starting to get agitated along
the remainder of the area of concern. Due to said confluence and
deeply unidirectional southwesterly flow, individual cells will
track northeastward with some potential for next core to repeat
before slow eastward propagation advances at 5-10kts. Given ample
moisture, rates of 2-2.5"/hr are possible resulting in similar
totals given the slower translation. However, as mentioned above,
weak mid-level waves could support some QLCS waves that allow for
increased E-W oriented outflow boundaries that would support
streaks of enhanced duration/training and perhaps even some
backbuilding along the upwind flank of said outflow boundaries.
This will present isolated parts of the line to support locally
3-4" totals presenting higher magnitude flash flooding potential
within the longer line of AoA local FFG exceedance.

Hydrologocally: Thunderstorms along the warm front continue to
translate northward across CT into MA away from best instability
due to persistent cloud cover, but have set the stage for wetting
the grounds for additional upstream development; while other
deeply saturated soil conditions exist across Central MD into
portions of Northern VA per NASA SPoRT 10-40cm relative soil
moisture ratios around 45-60% and AHPS indicating areas of
300-500% of normal. These area would be more at risk as well. As
such, flash flooding is considered possible through the length of
the MPD has a whole, but there will be isolated instances of flash
flooding through the evening.

Gallina

ATTN...WFO...AKQ...ALY...BGM...BOX...CTP...LWX...OKX...PHI...
RNK...

ATTN...RFC...MARFC...NERFC...SERFC...NWC...

LAT...LON 42087388 41967270 41287269 40677341 39417530
38517634 37167858 37447999 38817892 40137719
41457529 41997441

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