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  • MESO: Mesoscale Discussion 1712

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Jul 18 23:04:12 2025
    ACUS11 KWNS 182303
    SWOMCD
    SPC MCD 182303=20
    MNZ000-SDZ000-190100-

    Mesoscale Discussion 1712
    NWS Storm Prediction Center Norman OK
    0603 PM CDT Fri Jul 18 2025

    Areas affected...Eastern South Dakota...southwest Minnesota

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

    Valid 182303Z - 190100Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Initial supercells will be capable of large hail, severe
    winds, and perhaps a tornado or two. Timing of widely scattered to
    scattered storm development is not clear, but should occur within
    the next few hours. Eventual upscale growth will lead to a greater
    wind threat with time. A watch is possible as convective trends
    warrant.

    DISCUSSION...Cloud cover has remained across eastern South Dakota
    this afternoon. This has hindered surface heating and several models
    are not handling this very well. Several CAM solutions from earlier
    today depicted storms would already be ongoing. Recent HRRR/RRFS
    runs suggest a more reasonable, later start. With a storm now having
    developed in northeast South Dakota, a gradual increase in storm
    coverage is probable over the next few hours. The 18Z OAX sounding
    showed a capping layer near 800 mb which likely extends northward to
    some extent. A subtle increase in mid-level ascent and a modest
    low-level jet this evening are the likely forcing mechanisms to help
    erode the modest capping.

    Given effective shear of 40-50 kts and MLCAPE of 1500-2000 J/kg,
    initial supercells will be capable of large hail and severe wind
    gusts. The increase in 850 mb flow this evening will enlarge
    low-level hodographs, but the overall tornado threat is less clear
    given the less than ideal low-level thermodyamic profiles.
    Convection is then expected to grow upscale by mid/late evening.
    Severe wind gusts would be the primary hazard after this occurs.

    ..Wendt/Hart.. 07/18/2025

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-HGJHGpSnOHYVf6txUPA1A_unjDne1NQ6c4257U6USOTXbTeCI3a5MnXAk63AY9yq4MYq-8YY= xq1L6MNVo3qE_MotTs$ for graphic product...

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

    LAT...LON 43859803 44189886 44349885 44639833 45309716 45519637
    45219550 44849479 44759469 44599467 44049491 43729546
    43519637 43589736 43859803=20

    MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
    MOST PROBABLE PEAK WIND GUST...55-70 MPH
    MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN


    =3D =3D =3D
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