• MESO: Mesoscale Discussion 1063

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Jun 22 20:42:26 2021
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    ACUS11 KWNS 222042
    SPC MCD 222041=20

    Mesoscale Discussion 1063
    NWS Storm Prediction Center Norman OK
    0341 PM CDT Tue Jun 22 2021

    Areas affected...Northeast Nebraska and western Iowa

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

    Valid 222041Z - 222245Z

    Probability of Watch Issuance...40 percent

    SUMMARY...A couple of strong to severe storms capable of mainly
    large hail and damaging winds possible this evening.

    DISCUSSION...Mid-level showers and occasional thunderstorms have
    been present across western Iowa for much of the day thus far. This
    activity is likely a manifestation of the mid-level moisture and
    steep lapse rates in a region of isentropic ascent. Therefore,
    if/when the MLCIN can erode across this region, surface based storm
    development is anticipated.=20

    A well developed cu field has been advancing eastward across
    Nebraska over the last few hours with its eastward extent closely
    following the -25 J/kg MLCIN contour from SPC mesoanalysis. Linear extrapolation and forecast MLCIN from the RAP would suggest this cu
    field may advance to near the NE/IA border between 21 and 22Z. This
    will be the most likely time for surface based storm development as
    a minimally capped low-level environment spreads beneath the plume
    of better mid-level moisture and isentropic ascent. The window of
    opportunity for storm based storm development is narrow, but the
    timing appears favorable and the HRRR also supports the idea of
    storms developing around 21Z in the region of Sioux City, IA.=20

    Any stronger storms which develop will likely be supercellular in
    nature given 50 to 55 kts of effective shear per OAX VWP. These
    storms will pose a threat for severe hail and damaging winds. Any
    storms which develop are only expected to last a few hours before
    boundary layer cooling and subsequent increasing inhibition will
    likely bring and end to strong storms. While storm intensity is
    expected to be sufficient for a severe thunderstorm watch, storm
    coverage and longevity may be too limited.

    ..Bentley/Hart.. 06/22/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!pMldf_PX9eT2Jvw9c4CTp5lM_jB34NmNT4_2tJdf4_pMvxZ-uFmgMf8GgHfU0lgRBmjl0iki$=
    for graphic product...


    LAT...LON 41229655 41789765 42329784 42789764 43019625 42429347
    41619263 41059274 40679348 40639438 40599545 41229655=20

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