• MESO: Mesoscale Discussion 1956

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Nov 18 00:58:07 2022
    ACUS11 KWNS 180058
    SWOMCD
    SPC MCD 180057=20
    NYZ000-180700-

    Mesoscale Discussion 1956
    NWS Storm Prediction Center Norman OK
    0657 PM CST Thu Nov 17 2022

    Areas affected...portions of extreme western New York

    Concerning...Heavy snow=20

    Valid 180057Z - 180700Z

    SUMMARY...2+ inch snowfall rates are expected to accompany a primary
    snowband near or just south of the Buffalo, NY area this evening
    into early tomorrow morning. Reduced visibility and crippling travel
    conditions are possible through the night.

    DISCUSSION...A mid-level impulse embedded within the broader
    cyclonic upper flow is traversing the Lower MI peninsula and is
    approaching Lakes Erie/Ontario and far western NY, with broader
    deep-layer ascent gradually increasing over the Upper Hudson Valley.
    The approach of this impulse is causing surface-700 mb winds to veer
    more southwesterly, paralleling the long axis of Lake Erie. As such,
    a primary snowband (also paralleling Lake Erie) is beginning to
    mature and align in a manner that is favorable for a long-duration
    heavy lake-effect snow event for or immediately south of the
    Buffalo, NY area. Mesoanalysis trends also show surface-700 mb
    cold-air advection over Lake Erie, with the -12C to -17C dendritic
    growth zone deepening and saturating. The cold-air advection atop a
    warmer water surface is also contributing to 7.5 C/km low-level
    lapse rates near the Lake Erie shoreline (per the 00Z BUF observed
    sounding), which may possibly steepen further to near 8.5 C/km
    tonight, increasing SBCAPE over water to near 250 J/kg.=20

    The increase in CAPE and deepening/saturating of the dendritic
    growth zone may support convective snow development within the
    primary snow band, with 2+ inch/hr snowfall rates and near-zero
    visibility possible. The heaviest snowfall is most likely after 03Z
    and may continuing to 12Z Friday morning (based on the latest runs
    of the HRRR and the 12Z HREF ensemble consensus). Should a prolonged
    period of 1-2 inch/hr snowfall rates occur, potentially crippling
    travel conditions may develop.

    ..Squitieri.. 11/18/2022

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_RuSEHOop-N7sfkDH5fw4A77S_BQXwi5HCPgrRLN34-78seJS1y9OW-2RvG0nDgEHJ_J-95wr= n9Q4vn0yOnVjwgZe3k$ for graphic product...

    ATTN...WFO...BUF...

    LAT...LON 42617916 42697906 42757894 42817889 42907892 42937895
    43037898 43087892 43097878 42977862 42747851 42577868
    42527886 42517910 42617916=20


    =3D =3D =3D
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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Aug 12 00:17:35 2023
    ACUS11 KWNS 120017
    SWOMCD
    SPC MCD 120016=20
    MIZ000-120145-

    Mesoscale Discussion 1956
    NWS Storm Prediction Center Norman OK
    0716 PM CDT Fri Aug 11 2023

    Areas affected...portions of eastern Lower MI

    Concerning...Severe potential...Watch unlikely=20

    Valid 120016Z - 120145Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Isolated strong to severe storms may continue for a couple
    more hours with a risk for damaging gusts and a brief tornado.
    Convective trends will be monitored for a weather watch, but
    uncertainty remains high.

    DISCUSSION...Over the last hour, storms have slowly intensified near
    a frontal zone in the wake of previous convection. The air mass has
    slowly modified but remains partially capped with 500-1000 J/kg of
    MLCAPE now evident on SPC mesoanalysis and the 00z DTX sounding.
    Mid-level flow has also increased slightly over the last hour with
    deep-layer shear now reaching 30-35 kt. Sufficient buoyancy and
    vertical shear exist to support a brief uptick in severe risk across
    parts of eastern lower MI. Semi-discrete mode may support transient
    supercells with occasional low-level rotation. The primary hazard
    should remain damaging wind gusts, but backed low-level winds may
    support a risk for a brief tornado with the more organized storms.
    Convection will gradually encounter a more hostile air mass farther
    east where temperatures are cooler and low-level inhibition is
    higher. The loss of diurnal heating also suggests a gradual
    downtrend in intensity is likely soon. Conditions will be monitored,
    but confidence in the longevity of the severe risk is low.

    ..Lyons/Thompson.. 08/12/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!5UbzWMrFQjMyOLel4Fq4xt9hc_JNj76ZjQCd-H37MxseGxIJcGK8jfPeUE7FVLb-JvvJJLIF1= ZaPcS0S5uxEXjUyeTo$ for graphic product...

    ATTN...WFO...DTX...IWX...GRR...

    LAT...LON 42088461 43008413 43418378 43448329 43268271 42948249
    42678255 42438273 42148299 41938315 41828336 41758363
    41788416 41838459 42088461=20


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