• MESO: Mesoscale Discussion 0568

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun May 9 17:15:10 2021
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    ACUS11 KWNS 091715
    SPC MCD 091714=20

    Mesoscale Discussion 0568
    NWS Storm Prediction Center Norman OK
    1214 PM CDT Sun May 09 2021

    Areas affected...Northeast TX...Far southeast OK...Much of
    AR...Northern LA/MS...Western TN

    Concerning...Severe potential...Watch likely=20

    Valid 091714Z - 091845Z

    Probability of Watch Issuance...80 percent

    SUMMARY...Severe thunderstorm development is expected this afternoon
    along a cold front. Watch issuance is likely by 18-19Z. Very large
    hail, damaging winds, and a couple of tornadoes will be possible.

    DISCUSSION...At 17Z, a cold front draped from the Ozarks region into
    north TX is moving eastward, with an outflow boundary located across
    northern AR. Elevated thunderstorm activity has been ongoing north
    of the outflow boundary across far northern AR, and also across
    portions of east TX/northwest LA, and separately across northern MS.
    Some threat for marginally severe hail will persist in the short
    term with this elevated activity.=20

    The greater severe threat is expected to evolve later this
    afternoon, near/south of the outflow boundary and along and east of
    the advancing cold front, where moderate-to-strong instability and
    sufficient deep-layer shear will favor the potential for organized
    convection, including a few supercells.=20

    Very steep midlevel lapse rates (noted in 12Z observed soundings)
    will support a threat of hail (potentially significant) with any
    semi-discrete supercells that can develop. Cell mergers and linear
    forcing along the cold front will likely result in some
    upscale-growing clusters later this afternoon, with a corresponding
    risk of damaging winds. Low-level flow/shear will tend to weaken
    with time, especially across the western portion of the threat area,
    but some tornado threat will be present with any stronger supercell
    this afternoon, especially over the Ark-La-Miss vicinity.=20

    Some uncertainty remains regarding the timing of surface-based
    initiation, but issuance of one or more watches is likely by 18-19Z
    as development becomes increasingly likely with time this afternoon.

    ..Dean/Thompson.. 05/09/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!uAJsvE5Is0mW1LQXgmgTKNumDHfBvihdNZiOmL1q78-AgLgeK6G1-QCmG-eq0JUnSLg7t-WJ$=
    for graphic product...


    LAT...LON 34009472 34259437 34489401 34799358 35199304 35489268
    36029208 36159071 36118915 36088809 34598835 33418962
    32799073 32299171 31669285 31229505 31269637 31999677
    32529662 33179591 33529534 34009472=20

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