• MESO: Mesoscale Discussion 1819

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun Oct 10 17:58:25 2021
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    ACUS11 KWNS 101758
    SPC MCD 101757=20

    Mesoscale Discussion 1819
    NWS Storm Prediction Center Norman OK
    1257 PM CDT Sun Oct 10 2021

    Areas affected...northern Minnesota

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

    Valid 101757Z - 102000Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Isolated to scattered strong storms, including a few
    supercells, may pose a risk for isolated hail, a brief tornado, and
    or strong wind gusts this afternoon. A weather watch is being

    DISCUSSION...As of 1730 UTC, WV satellite imagery showed a
    pronounced upper low moving northeastward across the northern Plains
    and upper Midwest. Strong mid-level height falls have been observed
    near and to the east of the low where a 995 mb surface cyclone was
    analyzed across eastern North Dakota. Near the surface low, visible
    imagery showed towering cumulus and shallow convection developing
    early this afternoon. Breaks in the clouds were allowing surface
    heating and destabilization of a relatively moist boundary layer
    with dewpoints near 60 F. As strong lift from the upper low and
    convergence along the bent back cold/occluded front continue to move
    northward, additional thunderstorm development appears likely across
    northern Minnesota by mid afternoon. Steep mid-level lapse rates
    near 7 C/km exist beneath the cold pocket aloft supporting around
    1000 J/kg of MLCAPE. Strong southwesterly mid-level flow is also
    aiding in strong wind profiles with effective shear upwards of 50
    kts. While buoyancy may limit the threat somewhat, the strong shear
    suggests that organized storms including supercells are likely. The
    steep lapse rates and favorable deep-layer shear will likely support
    a hail risk with the stronger cores that develop. Backed surface
    flow east of the low may also support a brief tornado with the
    stronger supercells.=20

    The severe risk is expected to gradually evolve with initial storms
    developing within cloud breaks close to the surface low early this
    afternoon. Despite cooler surface temperatures, dynamic lift should
    continue to support a severe risk as storms move northward toward
    the Canadian border. Farther east across the Arrowhead, dense cloud
    cover and cooler temperatures have remained in place through much of
    the morning. Model soundings show inhibition remains strong enough
    to limit deep convection, casting doubt on the eastward extent of
    the severe threat. Better clearing and rapid warm advection across
    northwestern Wisconsin behind a warm front is evident on visible
    imagery, hinting that storms may develop farther south later this
    afternoon. Exact convective evolution of these storms is unclear
    given the less favorable environment northward. Nonetheless, a
    severe risk appears likely to evolve this afternoon with a risk for
    hail and tornadoes/damaging wind gusts. A weather watch is possible.

    ..Lyons/Hart.. 10/10/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!t9kxnaA52VFpC15g-4xgN-BRYqli0QJo5uuWiFI1KF89uei7a6O8AwkaAu700kXgUbj2HIEG$=
    for graphic product...


    LAT...LON 47329092 47099127 46919182 46859266 47209373 48299478
    48989508 48849408 48729346 48649258 48539199 48399146
    48279124 48059088 47889081 47629080 47329092=20

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