• MESO: Mesoscale Discussion 1787

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Sep 28 20:17:19 2021
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    ACUS11 KWNS 282017
    SPC MCD 282016=20

    Mesoscale Discussion 1787
    NWS Storm Prediction Center Norman OK
    0316 PM CDT Tue Sep 28 2021

    Areas affected...Parts of northwestern/northern Virginia

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

    Valid 282016Z - 282215Z

    Probability of Watch Issuance...5 percent

    SUMMARY...Widely scattered strong storms may develop through 5-7 PM
    EDT, and pose at least some risk for severe hail and locally strong
    wind gusts, particularly near and east/south of the Charlottesville

    DISCUSSION...To the north of a weakening mid-level speed maximum
    (around 40 kt near the 500 mb level) propagating across the Roanoke
    vicinity, the latest Rapid Refresh suggests that boundary-layer
    destabilization may become maximized during the next few hours along
    and to the lee of the Blue Ridge. Beneath an elongated mid-level
    cold pocket aligned along this corridor, lower/mid tropospheric
    lapse rates are becoming rather steep, with sufficient low-level
    moisture to contribute to mixed-layer CAPE in excess of 1000 J/kg,
    and perhaps locally as large as 2000 J/kg.

    Mid/upper forcing for ascent to support thunderstorm initiation is
    unclear, but widely scattered areas of deepening convective
    development are becoming evident along the higher terrain. This
    includes one area to the northwest of Charlottesville (near
    Staunton), where 2-3 mb 2-hourly surface pressure falls were
    apparent in 19Z observational data. In the presence of deep-layer
    shear at least marginally supportive of organized thunderstorm
    development, the environment appears conducive to widely scattered
    storms, perhaps including an isolated supercell structure or two,
    capable of producing severe hail. Locally strong surface gusts also
    appear possible, before activity weakens this evening with the loss
    of daytime heating.

    ..Kerr/Thompson.. 09/28/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!qyg7dkRd4TNBy-i9v9mLm06jwQ5fjKJ3ZNfpzwOgYPU8UQ1vlnl6_2wudmT2dmUKTGPoqdR3$=
    for graphic product...


    LAT...LON 38837776 38617741 38287738 38077755 37917782 37547860
    37817922 38367894 38757823 38837776=20

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