• MESO: Mesoscale Discussion 1176

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wednesday, June 15, 2022 18:23:16
    ACUS11 KWNS 151823
    SWOMCD
    SPC MCD 151822=20
    WIZ000-ILZ000-IAZ000-MNZ000-152015-

    Mesoscale Discussion 1176
    NWS Storm Prediction Center Norman OK
    0122 PM CDT Wed Jun 15 2022

    Areas affected...northeast IA...extreme southeast MN...portions of southern/central WI and extreme northwest IL

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

    Valid 151822Z - 152015Z

    Probability of Watch Issuance...95 percent

    SUMMARY...Convection is expected to develop across northeast IA and
    spread northeast in the next couple of hours. Tornadoes, damaging
    gusts and hail will all be possible. A tornado watch will likely be
    needed by 20z.

    DISCUSSION...Visible satellite and radar data from KDMX indicate
    deepening cumulus across northeast IA to the northeast of a surface
    low and in the vicinity of a surface warm front. More isolated
    cumulus has also started to develop across southern WI. Latest water
    vapor imagery indicates a shortwave impulse now ejecting across
    eastern NE/southeast SD will lift east/northeast, providing
    increasing ascent across the region within the next couple of hours.
    Some weak inhibition likely remains in the vicinity of the surface
    boundary, though continued heating and increasing ascent should
    rapidly erode any remaining inhibition over the next hour.

    Strong heating south of the surface boundary across IA into central
    WI has allowed temperatures to warm into the mid/upper 80s amid
    upper 60s to low 70s F dewpoints. Relatively warm temperatures
    between 850-700 mb will maintain modestly steep midlevel lapse
    rates, but the very moist boundary layer is still supporting
    moderate instability across the region. Effective shear magnitudes
    greater than 50 kt will further support robust, well-organized
    convection. Some uncertainty remains with regards to convective
    mode, but semi-discrete supercells appear possible at least
    initially in convective evolution. VWP data from KARX already shows
    enlarged, favorably curved low-level hodographs supporting rotation. Additionally, strong low-level instability with enhance vorticity in
    the vicinity of the surface front suggests increased tornado
    potential will accompany any semi-discrete convection.

    With time, convection is expected to grow upscale as a 35+ kt south/southwesterly low-level jet increases by late afternoon/early
    evening. This will result in an increasing risk for more widespread
    damaging gusts, though mesovortex tornadoes also will continue to be
    possible given favorable low-level shear.

    ..Leitman/Guyer.. 06/15/2022

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!4JbnpAdedRKbonPxvfVuUHT-vcgDEZIGTIZ_qpqGQnjBlYi4Z58B4PE3HaDxom7Hwt1n2gjo4= kyqDZeNeqf4hR9hZJs$ for graphic product...

    ATTN...WFO...GRB...LOT...MKX...DVN...ARX...DMX...

    LAT...LON 42379320 42699312 42819308 43229273 43729207 43959172
    44359099 44549056 44709020 44658991 44558962 44348923
    44028883 43758870 43448859 42978862 42668883 42328935
    42009017 41809157 41809233 41919281 42119309 42379320=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tuesday, June 20, 2023 20:14:44
    ACUS11 KWNS 202014
    SWOMCD
    SPC MCD 202014=20
    SDZ000-NDZ000-NEZ000-202145-

    Mesoscale Discussion 1176
    NWS Storm Prediction Center Norman OK
    0314 PM CDT Tue Jun 20 2023

    Areas affected...portions of the western into central Dakotas

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

    Valid 202014Z - 202145Z

    Probability of Watch Issuance...80 percent

    SUMMARY...The severe threat is increasing across western and central
    parts of both North Dakota and South Dakota, with large hail and
    severe gusts the primary hazards. A Severe Thunderstorm Watch
    issuance will likely be needed.

    DISCUSSION...Convective initiation is underway ahead of an
    approaching surface cold front, driven by low-level deep-moisture
    convergence, and gradually increasing upper-level divergence
    associated with the approaching mid-level trough. Mostly clear skies
    ahead of the cold front has allowed for ample destabilization of the
    boundary layer. Surface temperatures have warmed to over 90 F, amid
    mid 60s F dewpoints, yielding over 3000 J/kg MLCAPE (given 7.5+ C/km
    mid-level lapse rates overspreading the Dakotas), with CINH erosion
    noted in the 20Z mesoanalysis. Mid-level flow is roughly parallel
    with the surface cold front, with the stronger speed shear (i.e. 40+
    kts of effective bulk shear) lagging the front to the west.
    Nonetheless, ample buoyancy and modest deep-layer shear attempting
    to precede the cold front will support the development of several
    multicell clusters, short line segments, and perhaps a transient
    supercell, all of which will be capable of producing severe
    hail/winds. Given the number of storms expected ahead of the surface
    cold front, a WW issuance will likely be needed.

    ..Squitieri/Hart.. 06/20/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-roqBmnrR7ZZaJsMGN95QC1hKKikoWQ8lFnDs-WSd3PRTtu4ajrXvKCBRFpwXPAo0LRsq4pyv= CZdcwvzT9hpNMjVR78$ for graphic product...

    ATTN...WFO...ABR...BIS...LBF...UNR...

    LAT...LON 45950224 47710157 48570087 48740030 47800020 45750018
    44540018 42980048 41990064 41550107 41600204 42770240
    43710239 45950224=20


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