• MESO: Mesoscale Discussion 0424

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Apr 24 18:23:05 2021
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    ACUS11 KWNS 241823
    SPC MCD 241822=20

    Mesoscale Discussion 0424
    NWS Storm Prediction Center Norman OK
    0122 PM CDT Sat Apr 24 2021

    Areas affected...portions of central and northern Alabama into far
    southern Middle Tennessee and extreme northwest Georgia

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

    Valid 241822Z - 242015Z

    Probability of Watch Issuance...40 percent

    SUMMARY...A gradual increase in storm coverage is expected over the
    next few hours. A couple of the stronger storms may produce
    marginally severe hail and perhaps a damaging gust or two. Severe
    coverage however, is expected to be somewhat limited by relatively
    marginal instability, though convective coverage will be monitored
    for the need of a Severe Thunderstorm Watch.

    DISCUSSION...The eastward progression of a surface low, along with
    continued heating, are expected to contribute enough low-level lift
    to support increasing convective coverage over the next few hours
    across portions of central and northern AL into far southern middle
    TN. Clearing skies are allowing for some modification of the
    boundary-layer, while the westward approach of a 7-7.5 C/km
    mid-level lapse rate plume will encourage some airmass
    destabilization while overspreading the modifying boundary layer.
    However, given the amount of overturning from earlier convection,
    the atmosphere is expected to only become marginally unstable, with
    500-1000 J/kg MLCAPE being common (with perhaps localized areas of
    1000-1500 J/kg possible). Nonetheless, 50-70 kts of effective bulk
    shear and the near 7.5 C/km mid-level lapse rates will promote at
    least marginally severe hail with the more intense storms. A couple
    damaging gusts may also occur with the stronger downdrafts.

    While convective coverage is expected to increase through the
    afternoon, severe coverage may be on the more sparse end, though a
    localized cluster of hail/damaging gust instances cannot be
    completely ruled out. As such, conditions will be monitored for the
    need of a Severe Thunderstorm Watch should a localized swath of
    severe hail/winds become evident in future observations/guidance

    ..Squitieri/Hart.. 04/24/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!rGHuX91MA6ABXQNkwr2fk75nyY_QokeM37WMFOhr3T4WON6BLkPu1ecanDDDHjywFm0DAb-D$=
    for graphic product...


    LAT...LON 33248565 33028705 33208819 33528833 34438821 34688806
    35288760 35498711 35528656 35478613 35368569 35118542
    34758513 34408508 34028520 33618543 33248565=20

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