• MESO: Mesoscale Discussion 0688

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed May 19 22:04:23 2021
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    ACUS11 KWNS 192204
    SPC MCD 192203=20

    Mesoscale Discussion 0688
    NWS Storm Prediction Center Norman OK
    0503 PM CDT Wed May 19 2021

    Areas affected...Eastern North Dakota

    Concerning...Severe potential...Watch unlikely=20

    Valid 192203Z - 200000Z

    Probability of Watch Issuance...5 percent

    SUMMARY...Brief landspouts and perhaps isolated instances of severe
    hail and/or damaging wind will remain possible through the early
    evening hours for parts of eastern North Dakota and extreme
    northwest Minnesota.

    DISCUSSION...Thunderstorm development has been ongoing over the past
    hour along a migratory cold front draped from far northwest MN into
    southern ND. Deep-layer flow across the region remains very weak and
    effective bulk shear values are expected to generally remain below
    30 knots, which will limit the overall severe potential. Despite
    this weakness, the environment does exhibit sufficient instability
    and steep 0-3 km lapse rates (near 8 C/km per RAP analyses and
    forecast soundings). These factors will support an isolated
    wind/hail threat with any stronger updrafts. Additionally, ambient environmental vorticity along the cold front, coupled with the steep
    low-level lapse rates, will continue to support the potential for
    brief landspout tornadoes (one such tornado has already been
    reported). It is unclear how long the landspout tornado threat will
    persist given the tendency for most storms to quickly become outflow
    dominant. However, new storm development along the front and/or
    outflow intersections may maintain the threat through sunset when boundary-layer decoupling begins. Given the isolated nature of the
    threat, a watch is not expected.

    ..Moore/Dial.. 05/19/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!oAsatf3ty0gJFmkfGuR6_w8U1qnFgxZLloEwJ3YRSqoL7RW1r2_wgGZkDy7Lo349s7biBzAc$=
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    LAT...LON 46390070 47339977 48169863 48809770 49079695 49049588
    48359631 47859703 47469757 46899831 46409900 46069989
    46060051 46390070=20

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