• MESO: Mesoscale Discussion 1272

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Jul 13 20:22:07 2021
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    ACUS11 KWNS 132021
    SPC MCD 132021=20

    Mesoscale Discussion 1272
    NWS Storm Prediction Center Norman OK
    0321 PM CDT Tue Jul 13 2021

    Areas affected...Southern MT...Northeast WY...Western SD...Northwest

    Concerning...Severe potential...Severe Thunderstorm Watch likely=20

    Valid 132021Z - 132145Z

    Probability of Watch Issuance...95 percent

    SUMMARY...The severe thunderstorm threat will gradually increase
    this afternoon, with isolated severe wind and hail possible. A more
    substantial threat for damaging wind is expected to develop by early
    evening. Watch issuance is likely for parts of the area by 21-22Z.

    DISCUSSION...A well-defined midlevel shortwave trough is noted
    across northwest MT at 20Z, with increasing cumulus and lightning
    activity in advance of the shortwave across south-central MT and
    north-central WY. Convection is expected to increase in coverage and
    intensity this afternoon as it moves east-southeastward into an
    increasingly unstable environment. Effective shear of 40+ kt will
    support organized storm structures as convection matures, with
    organized clusters and perhaps a supercell or two possible by late
    afternoon, posing a threat of locally severe wind and hail.=20

    With time, convection is expected to evolve into a large cluster and
    perhaps a well-organized MCS by early evening, as outflows
    consolidate within an environment characterized by steep
    low/midlevel lapse rates. As this occurs, the threat for more
    widespread damaging wind will increase from northeast WY into the
    Black Hills region of SD and Sand Hills region of NE, with some
    gusts in excess of 65 kt possible. Severe Thunderstorm Watch
    issuance for portions of the area is likely by 21-22Z.

    ..Dean/Dial.. 07/13/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!o1pvhtAwujeT8nrytOR1FL2pnJZu3ihQmHMmBkkQ1P4flJ4lE4eqp-9UFZdiRDe0fux6pXRj$=
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    LAT...LON 46200904 45760657 45430530 45140429 44420280 43750228
    42720191 42240190 41910220 42010306 42080366 42220457
    42700589 43310718 44950934 45470918 45790913 46200904=20

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