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  • MESO: Mesoscale Discussion 1389

    From COD Weather Processor@1:2320/127 to wx-storm@lists.illinois.edu on Tue Jun 30 01:59:59 2026
    ACUS11 KWNS 300159
    SWOMCD
    SPC MCD 300159=20
    MNZ000-IAZ000-SDZ000-NEZ000-300330-

    Mesoscale Discussion 1389
    NWS Storm Prediction Center Norman OK
    0859 PM CDT Mon Jun 29 2026

    Areas affected...portions of southeastern South Dakota into
    northwestern Iowa and southwestern Minnesota

    Concerning...Severe Thunderstorm Watch 417...

    Valid 300159Z - 300330Z

    The severe weather threat for Severe Thunderstorm Watch 417
    continues.

    SUMMARY...Developing thunderstorms will continue to grow upscale
    over the next 1-2 hours with a transition towards severe wind gusts
    of 60-80 mph as the primary threat. Large hail also remains
    possible.

    DISCUSSION...Thunderstorm coverage has gradually increased along an eastward-progressing cold front across portions of eastern South
    Dakota and western Minnesota over the past hour. As this development
    continues, rapid upscale growth into one or more bowing complexes is anticipated over the next 1-2 hours. Aided by strong to extreme
    instability and steep mid-level lapse rates (5000-6000 J/kg MLCAPE
    and 9+ C/km, respectively, indicated by latest objective analysis
    and sampled by regional 00z observed soundings), rich boundary layer
    moisture, and strong effective shear of 50-60 kts, this transition
    to a more linear mode will favor an increase in the risk for severe
    wind gusts of 60-80 mph as convection evolves eastward. Large to
    very large hail to 2" in diameter also remains possible,
    particularly with any supercells that can remain semi-discrete.

    ..Chalmers.. 06/30/2026

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-Ze1DDYgl2DHoEBDrDfIImF5t_st1eJn8a5XBLIaDhRurVDS71ThunnUsgtnCbWwhuIeXudqN= AOPtE145ldZWfqUCSE$ for graphic product...

    ATTN...WFO...MPX...DMX...FSD...ABR...

    LAT...LON 42769694 43249668 44119608 44759607 44829606 45249610
    45529607 45709604 45759575 45839533 45799485 45709457
    45549430 45269418 44719415 44069430 43549458 42999518
    42829564 42599685 42769694=20

    MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
    MOST PROBABLE PEAK WIND GUST...65-80 MPH
    MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN


    =3D =3D =3D
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    * Origin: Capitol City Weather Station (1:2320/127)