• MESO: Mesoscale Discussion 1762

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Sep 17 00:16:25 2021
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    ACUS11 KWNS 170016
    SPC MCD 170015=20

    Mesoscale Discussion 1762
    NWS Storm Prediction Center Norman OK
    0715 PM CDT Thu Sep 16 2021

    Areas affected...Northern Nebraska and southeast South Dakota

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

    Valid 170015Z - 170215Z

    Probability of Watch Issuance...40 percent

    SUMMARY...Strong to severe thunderstorms remain likely this evening
    and into the overnight hours across northern Nebraska into southeast
    South Dakota. Damaging winds and hail will be possible, and a watch
    may be needed in the coming hours.

    DISCUSSION...Latest GOES visible and IR imagery show some hints at
    increasing lift in the vicinity of a surface low in western NE and
    along a cold front draped across northern NE - mainly in the form of
    cooling cloud tops within the stratus deck and increasing cloud
    cover along the frontal zone. A few convective towers with transient
    lightning have also been noted near Alliance, NE. Although sunset in
    the coming hour will result in an increase in surface-based
    inhibition through the evening, a strengthening low-level jet (the
    onset of which is noted in recent KGLD VWP obs) impinging on the
    frontal zone will maintain lift over the region and likely support
    MU parcels reaching their LFCs. 1000-2000 J/kg MUCAPE and 35-45
    knots of effective bulk shear will support the potential for
    organized convection. Deep-layer shear vectors and initial storm
    motions along and slightly behind the cold front will likely support semi-discrete to linear storm modes. A severe hail/wind threat
    appears likely, and may be augmented if 1) effective bulk shear
    increases to near 60 knots - as suggested by some recent model runs,
    or 2) if a storm can become rooted within the boundary layer on the
    warm side of the front where weaker near-surface thermal inversions
    may support a higher wind threat. A watch may be needed in the
    coming hours to address this scenario as confidence in sustained
    convective initiation increases.

    ..Moore/Edwards.. 09/17/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!oqTiyPhJ6xcNpj9zvaRNcmD3vlX0ZA5FRYI83eOyvlQ_p8tKPuUEJzlNAAwl6fPAaQWWekbQ$=
    for graphic product...


    LAT...LON 41710041 41620137 41580227 41650307 42490319 42890268
    42910128 42980012 43269898 43619820 43309732 42619752
    42319822 42129883 41889960 41710041=20

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