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  • MESO: Mesoscale Discussion 1621

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Jul 18 22:43:00 2023
    ACUS11 KWNS 182242
    SWOMCD
    SPC MCD 182242=20
    NDZ000-SDZ000-190045-

    Mesoscale Discussion 1621
    NWS Storm Prediction Center Norman OK
    0542 PM CDT Tue Jul 18 2023

    Areas affected...portions of central/eastern ND/SD

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

    Valid 182242Z - 190045Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Isolated to widely scattered strong to severe
    thunderstorms are expected by 00z. Large hail will be the main
    hazard with this activity. A watch may be needed in the next couple
    of hours.

    DISCUSSION...Southerly low-level flow ahead of a sharpening and southeastward-advancing cold front has allowed for a corridor of
    mid/upper 60s F dewpoints to overspread much of central ND/SD.
    Dewpoints decrease to the upper 50s/low 60s over the eastern
    Dakotas. Pockets of strong heating and steep midlevel lapse rates
    have allowed for moderate to strong destabilization. Warm advection
    is resulting in some cloudiness on the eastern periphery of stronger instability, and some elevated weak convection is currently ongoing.
    However, further west closer to the cold front and zone of stronger
    low-level convergence, deepening cumulus has been noted in visible
    satellite. As stronger ascent spreads eastward this evening,
    isolated to widely scattered thunderstorm development is expected.

    Low-level flow will remain rather weak, but effective shear
    magnitudes greater than 40 kt will support organized cells.
    Elongated hodographs, in conjunction with steep midlevel lapse rates
    and 30-40 kt westerly flow between 3-6 km suggest large (and
    possibly isolated very large/2+ inch diameter) hail will be possible
    with this activity. Timing of convective development is a little
    uncertain, but the severe risk is expected to increase by 00z, and a
    severe thunderstorm watch may be needed in the next couple of hours.

    ..Leitman/Edwards.. 07/18/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!_5hg6BJf6I0_2ZeKOJ-QO9UdfSvIxkD1B-C05-TukQaZItEEIXvrj6Y4qyIN8G9AGAqzi6YYg= kXJDaQNPGRMqrC1v_I$ for graphic product...

    ATTN...WFO...FGF...FSD...ABR...BIS...UNR...

    LAT...LON 44580116 46370112 47460101 48070080 48419999 48509910
    48329851 47979790 47379761 46629753 45769754 44259824
    43859897 43819958 43810013 43960067 44580116=20


    =3D =3D =3D
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