• MESO: Mesoscale Discussion 1550

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Aug 18 12:47:16 2021
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    ACUS11 KWNS 181247
    SPC MCD 181246=20

    Mesoscale Discussion 1550
    NWS Storm Prediction Center Norman OK
    0746 AM CDT Wed Aug 18 2021

    Areas affected...Parts of the eastern West Virginia
    Panhandle...northern Virginia...central Maryland and adjacent south
    central Pennsylvania

    Concerning...Severe potential...Watch possible=20

    Valid 181246Z - 181445Z

    Probability of Watch Issuance...40 percent

    SUMMARY...The development of occasional isolated supercell
    structures with the potential to produce tornadoes (generally
    short-lived) may increase through 11 am-1 pm EDT, mainly west
    through northwest of the District of Columbia into the higher
    terrain around Martinsburg, WV and Hagerstown, MD. It is not yet
    certain a watch will be needed, but trends are being monitored for
    this possibility.

    DISCUSSION...The remnant surface low of Fred has migrated northward
    into areas south/southeast of Parkersburg, WV during the past few
    hours. As this has occurred, very moist boundary layer has advected northwestward across the Mid Atlantic region. This includes dew
    points as high as the mid 70s F into the higher terrain centered
    around the Martinsburg, WV vicinity, where low-level convergence is
    becoming focused, and an area of enhanced mid/upper forcing for
    ascent is forecast to overspread through 15-17Z. Beneath a narrow
    belt of 30+ kt southerly flow around 850 mb, this also appears
    likely to coincide with where clockwise-curved low-level hodographs
    will become maximized, with the terrain contributing to the
    maintenance of backed/southeasterly near surface flow. As breaks in
    the overcast allow for insolation to contribute to boundary-layer destabilization, it appears that the environment may become
    increasingly conducive to supercell structures with the potential to
    produce relatively short-lived tornadoes.

    ..Kerr/Edwards.. 08/18/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!vImGjF_GzfDbr1COaknxAQItDQID34TLrbZH7dvQBbcGQMACI5GOvyUQlXd45P267IS-ssbe$=
    for graphic product...


    LAT...LON 39777813 39787740 39007724 38347764 38807819 39777813=20

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