AWUS01 KWNH 071808
FFGMPD
FLZ000-072300-
Mesoscale Precipitation Discussion 0310
NWS Weather Prediction Center College Park MD
206 PM EDT Tue Jun 07 2022
Areas affected...South Florida
Concerning...Heavy rainfall...Flash flooding possible
Valid 071800Z - 072300Z
SUMMARY...Additional development of deep moist convection this
afternoon is expected across South Florida. Hourly rainfall rates
2"/hr may lead to areas of flash flooding, particularly in more
urbanized communities.
DISCUSSION...Doppler Radar continues to identify a congealed area
of strong thunderstorms near the Lower Florida Keys and extending
on north into the Everglades. KAMX base velocities have picked up
on an outflow boundary tracking north towards the Miami metro area
with convection beginning to flare up along this boundary, as well
as along the sea breeze positioned several miles farther inland.
The atmosphere remains primed to produce torrential rainfall
rates. Mesoanalysis shows the area has up to 3,000 J/kg worth of
MLCAPE at these storms disposal and PWs of 2.0-2.3". Area averaged
soundings at 20Z today from the latest HRRR show mean cloud layer
vertical wind shear between 30-35 knots, which is largely driven
by the faster 500-250mb winds aloft. This has likely aided in the
better organized convection so far just south of the mainland.
Mean cloud layer winds are also quite weak, generally not topping
any higher than 10 knots. This is a recipe for building areas of
convection that can be maintained slightly longer than typical
pulse storms, and slow storm motions would give storms a little
longer residency time.
The upper trough will continue to provide some effective mid-layer
shear given the presence of the upper trough to the west, as well
as some diffluent flow aloft. The 12Z HREF did indicate a >40%
probability area for 3-hr QPF exceeding 3-hr flash flood guidance
between 18-21Z near and just west of the Miami metro. As the
outflow boundary advances north, convection will continue to
ignite additional convection as far north as Lake Okeechobee,
which will continue into the early evening hours. As daytime
heating concludes, areas of convection will eventually dissipate.
South Florida still contains lingering saturated soil throughout
the region with FLASH CREST soil saturation ranging between 50-75%
in spots. Along with the urban corridor near Miami and points
north, it is in these areas with higher soil saturation and in
more urbanized locations that are most at risk for possible flash
flooding this afternoon.
Mullinax
ATTN...WFO...KEY...MFL...
ATTN...RFC...SERFC...NWC...
LAT...LON 26978130 26918065 26537982 25747990 25398020
25148055 25168105 25408146 25878176 26398157
= = =
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