• MESO: Mesoscale Discussion 1452

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Aug 9 19:57:23 2021
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    ACUS11 KWNS 091957
    SPC MCD 091956=20

    Mesoscale Discussion 1452
    NWS Storm Prediction Center Norman OK
    0256 PM CDT Mon Aug 09 2021

    Areas affected...Portions of central and eastern North Dakota.

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

    Valid 091956Z - 092200Z

    Probability of Watch Issuance...80 percent

    SUMMARY...Severe thunderstorm development is expected within the
    next 1 to 2 hours. Large hail, damaging winds, and perhaps a tornado
    are all possible.

    DISCUSSION...19Z surface analysis shows a ~1006mb surface low near
    Sheridan, North Dakota. Extending east front this surface low is a
    stationary front which extends into northwest Minnesota. This
    boundary has been reinforced by precipitation for much of the
    morning, but now that convection is waning, may begin to lift north
    as a warm front through the afternoon and evening. In addition, a
    cold front extends from near this surface low southward to central
    South Dakota.=20

    Deep-layer ascent has started to spread eastward ahead of an
    approaching upper-level low with expanding cloud cover and some
    elevated convection across northwest North Dakota. In the last 30
    minutes, some low-level cumulus has started to develop near the
    low-pressure center and extending southward along the cold front.
    Vertical development currently appears limited, and SPC mesoanalysis
    still shows inhibition across the region. However, expect this
    inhibition to erode over the next 1 to 2 hours as stronger ascent
    arrives. The environment is favorable for supercells given around
    1500 J/kg MLCAPE (forecast to increase above 2000 J/kg) and
    effective shear around 40 to 50 knots per SPC mesoanalysis.=20

    Large hail will likely be the primary threat given the storm mode,
    steep mid-level lapse rates, and storm motion which will likely
    cause storms to move to the cool side of the stationary front and
    perhaps become elevated. However, there will also be a threat for
    severe wind and perhaps a tornado or two. The best tornado potential
    would likely be along or maybe slightly on the northern side of the
    stationary front where enough warming has occurred for surface based
    storm development in a region with significantly backed surface
    winds. Weak winds (<20 knots) in the lowest 2km per regional RAOBs
    will also be a limiting factor to a greater tornado threat.=20

    A watch is likely within the hour.

    ..Bentley/Thompson.. 08/09/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!te2q3vlG_aLqOJzJkTN87cR5YRx2yAELyFUTRo3v6iEpEFgMjZ6PS2gPR7bsnztzPqjJarRl$=
    for graphic product...


    LAT...LON 48110124 49020053 49089718 48499716 47079698 46599706
    46319920 46650051 48110124=20

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