• MESO: Mesoscale Discussion 1693

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Sep 4 19:21:21 2021
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    ACUS11 KWNS 041921
    SPC MCD 041920=20

    Mesoscale Discussion 1693
    NWS Storm Prediction Center Norman OK
    0220 PM CDT Sat Sep 04 2021

    Areas affected...Parts of south central into southeastern Missouri

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

    Valid 041920Z - 042115Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Thunderstorms may continue to intensify and develop into a
    small organizing cluster across south central into southeastern
    Missouri this afternoon, possibly accompanied by increasing
    potential for strong to severe wind gusts while approaching the
    Farmington, Poplar Bluff and Cape Girardeau areas through 4-6 PM
    CDT. It not clear that a severe weather watch is needed, but trends
    will continue to be monitored.

    DISCUSSION...There has been some recent intensification of
    convection and initiation of thunderstorms to the south/southeast of
    Lebanon, MO. This appears to be occurring near the intersection of
    a weak southward advancing surface front (enhanced to some degree by
    convective outflow) and a zone of strengthening differential surface
    heating along the southern fringe of remnant early day convective
    cloud cover and rainfall. This also appears immediately ahead of
    weak mid-level troughing migrating across the lower Missouri/middle
    Mississippi Valleys.

    The zone of differential surface heating coincides with a corridor
    of moderate deep-layer vertical shear, beneath 30-50 kt westerly
    flow in the 700-500 mb layer, and extends across southern Missouri,
    toward the Cape Girardeau area. Warm advection along and to the
    immediate cool side of this surface boundary will contribute to
    large-scale ascent, and may support continuing upscale convective
    growth through this afternoon.=20=20

    With modest southerly system-relative low-level wind fields
    contributing to inflow of seasonably moist air boundary-layer air (characterized by CAPE of 1000-2000 J/kg) from along and south of
    the front, the evolution of a small increasingly organized
    convective system appears possible. Although lower/mid tropospheric
    lapse rates are generally modest to weak, precipitation loading
    coupled with downward momentum transfer may gradually contribute to
    the risk for strong surface gusts approaching or briefly exceeding
    severe limits.

    ..Kerr/Bunting.. 09/04/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!tYdbejcQP5ElwgbExCpcZ0doO4N4DCSdveMP8fW9kvemoUKucwSKWkt1djpJuBYwEKlM9YWl$=
    for graphic product...


    LAT...LON 37379214 37979155 37698990 36929093 37009276 37379214=20

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