• MESO: Mesoscale Discussion 1343

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Jul 24 22:21:46 2021
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    ACUS11 KWNS 242221
    SPC MCD 242221=20

    Mesoscale Discussion 1343
    NWS Storm Prediction Center Norman OK
    0521 PM CDT Sat Jul 24 2021

    Areas affected...portions of central and southern Lower
    MI...northern IN...northern IL...southernmost Lake Michigan...west-central/southwestern Lake Huron.

    Concerning...Severe Thunderstorm Watch 390...391...

    Valid 242221Z - 250015Z

    The severe weather threat for Severe Thunderstorm Watch 390, 391

    SUMMARY...Bands of thunderstorms from northern IL to southern Lower
    MI will continue to offer sporadic damaging gusts and large hail
    through the 02Z and 03Z nominal expiration of WW 390 and 391,

    DISCUSSION...As of 22Z, bands of convection were evident across central/southern Lower MI, with visible satellite imagery and radar
    composited indicating linkage occurring to initially separate
    activity over southern Lake Michigan and northern IL. The resulting
    primary convective band should be the main severe-weather concern
    over the remainder of the watch areas, with less (but nonzero)
    threat from trailing activity southwest of the MBS area.=20

    The modified 18Z DTX sounding and model soundings indicate that
    surface insolation and lower 70s F dew points are supporting MLCAPE
    in the 1000-2000 J/kg range over southern Lower MI, transitioning to
    2000-3000 J/kg over northern IL. Convergence is (and should remain)
    weaker over northwestern IL, reducing convective/severe potential
    there, even with greater buoyancy. Despite veered/southwesterly
    surface winds, favorable deep shear will remain across northeastern
    IL, northern IN and southern MI, with 35-45-kt northwesterly
    effective-shear vectors being common over the region. Though slow
    evening cooling of the preconvective boundary layer is expected, the
    rich moisture will make the process gradual, helping to maintain
    surface-based effective-inflow parcels for several more hours.=20

    Five counties in southeastern Lower MI (including most of the DTW
    area) have been added to WW 390. Potential for severe thunderstorms
    to extend past 02Z will be evaluated in the coming couple hours to
    determine if any new watch(es) will be needed for this evening past
    02Z and/or extending farther southeastward.

    ..Edwards.. 07/24/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!pZr2X4nm0UlO-ANHHJEMMCmB0I2e4cCd90Q3iuCOb5HpwvkAXGxUtgsrLc9JavmkA9VIEAPa$=
    for graphic product...


    LAT...LON 41578981 42078799 42118660 43478601 43978401 44658235
    43338227 41888332 41698480 41068603 40318882 40628982

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