• MESO: Mesoscale Discussion 1200

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thu Jul 8 19:16:20 2021
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    ACUS11 KWNS 081916
    SPC MCD 081915=20

    Mesoscale Discussion 1200
    NWS Storm Prediction Center Norman OK
    0215 PM CDT Thu Jul 08 2021

    Areas affected...portions of north-central and eastern Montana

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

    Valid 081915Z - 082015Z

    Probability of Watch Issuance...60 percent

    SUMMARY...A supercell has recently evolved across Montana and severe
    weather appears possible with this storm as it move to the east
    southeast. Additional development and a greater severe risk later in
    the day appears likely. A watch is possible but uncertain in the
    short term, with greater confidence in the need for a watch later
    this afternoon.

    DISCUSSION...A lone supercell in Phillips County, MT has intensified
    over the last half hour as it continues to track into destabilizing
    airmass across central and eastern Montana. Ahead of a progressive
    mid-level vort max, forcing for ascent and insolation will continue
    to remove mixed-layer inhibition over the next several hours,
    setting the stage for additional thunderstorm development. With
    continued destabilization, spc mesoanalysis and RAP forecast
    soundings show 1500-2000 J/kg of MLCAPE developing by late
    afternoon. As this cell, and potentially others, track eastward into
    the instability corridor, additional strengthening appears possible.

    Ahead of the vort max, mid-level shear profiles are robust, with
    45-55 kts of effective shear supporting a supercellular storm mode.
    Mid-level lapse rates near 8 C/km will support large to very large
    hail. Damaging wind gusts also appear to be a significant threat,
    given temperature dewpoint spreads near 30 F. While a tornado cannot
    be ruled out given a favorable storm mode, it does not appear likely
    with higher LCLs and weaker low-level shear profiles.

    Th severe threat posed by the current storm will most likely remain
    isolated over the next several hours given, casting doubt on the
    need for a weather watch in the short term. However, additional
    storm development appears probable later this afternoon/evening as
    the main vort max continues to eject eastward. Hi-res guidance
    signals continue to suggest a more widespread severe weather threat
    developing across the region this evening where a watch would likely
    be needed. Convective trends Will continue to be monitored.

    ..Lyons/Guyer.. 07/08/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!qOm8msJL7_lZXzzuM1SuNFW7uuMVy9BZc-vP7NO_G3Jsd4cZr_Qkcacas2ZQ40vqqu2RfyK7$=
    for graphic product...


    LAT...LON 47410708 47530771 47850853 48620870 49050817 49070759
    49090635 49080571 49020526 48610463 48170426 47460423
    46940444 46630507 47010608 47410708=20

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