• MESO: Mesoscale Discussion 1183

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Jul 7 20:04:11 2021
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    ACUS11 KWNS 072004
    SPC MCD 072003=20

    Mesoscale Discussion 1183
    NWS Storm Prediction Center Norman OK
    0303 PM CDT Wed Jul 07 2021

    Areas affected...south central Montana

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

    Valid 072003Z - 072200Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Severe storms, including a few supercells, are forecast to
    develop north of a warm front with a risk for damaging winds and
    hail into this evening. A weather watch may be needed.

    DISCUSSION...Downstream of a shortwave trough across the Pacific
    Northwest, showers and a few thunderstorms have developed across
    portions of western Montana and eastern Idaho. As additional lift/destabilization develops ahead of the approaching trough,
    convective coverage/intensity should increase late this afternoon
    and early this evening. Warm and moist surface conditions with T/TDs
    in the 80s/50s F respectively are contributing to between 500 and
    1000 J/kg of MLCAPE across much of Montana. While some inhibition
    remains, it should reach diurnal minimum over the next couple of
    hours coincident with increased forcing for ascent from the trough
    aloft. Additional storm development appears increasingly likely by
    21-23z within a moderately sheared airmass (effective shear 40-50
    kts). Supercells and short line segments appear to be the dominant
    storm mode as high-based convection moves out of the mountains into
    deeper moisture and becomes better organized. With steep low and
    mid-level lapse rates in place, damaging wind gusts and severe hail
    will be the primary threats. Later this evening, upscale growth into
    one or two convective clusters/line segments may present an enhanced
    corridor of wind damage potential downstream across portions for
    central and eastern Montana. Here, greater vertical shear may
    support a more organized storm mode capable of strong wind gusts, a
    few of which could be significant.=20

    Convective trends are being monitored for a possible weather watch=20
    around the 22-00z time frame.

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

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!sCAt2iJv4_b3w64zNJPwEbsSNozyfwb8avu-OOFf7ETx5fteF3wrBXAJfwSYwNeO-yWrWVAD$=
    for graphic product...


    LAT...LON 46020538 45490735 45480892 45371062 45401092 46021187
    47021189 47571091 47830964 47980739 47980715 47920674
    47640573 47300534 46640513 46020538=20

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