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  • MESO: Mesoscale Discussion 2054

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Dec 21 16:33:40 2022
    ACUS11 KWNS 211633
    SWOMCD
    SPC MCD 211633=20
    WIZ000-MNZ000-IAZ000-SDZ000-212030-

    Mesoscale Discussion 2054
    NWS Storm Prediction Center Norman OK
    1033 AM CST Wed Dec 21 2022

    Areas affected...Southeast South Dakota...far northwest
    Iowa...southern Minnesota into far northwest Wisconsin

    Concerning...Heavy snow=20

    Valid 211633Z - 212030Z

    SUMMARY...The potential for heavy snowfall rates between 1-2 inches
    per hour is expected to increase through the late morning and early
    afternoon from the mid Missouri River Valley to the upper
    Mississippi River Valley.

    DISCUSSION...Regional radar mosaics from the past 1-3 hours show an
    elongated zone of increasing reflectivity values from eastern SD to
    southern MN. This is likely in response to strengthening isentropic
    ascent in the 925-700 mb layer within a broad warm frontal zone
    draped across the region. This mesoscale ascent is augmenting more
    broad, synoptic lift ahead of an approaching shortwave trough over
    the northern Plains, and is supporting an increase in coverage of
    moderate, to at times heavy, snowfall rates per latest surface
    observations and regional web cams. Latest guidance suggests that
    this trend should continue through at least early afternoon as the
    synoptic low continues east/southeast and saturation of the lowest
    1-2 km continues. Forecast soundings indicate that much of the
    low/mid-level ascent coincides with a ~100 mb deep dendritic growth
    zone, which will favor efficient snow production and the potential
    for heavy snowfall rates around 1 inch per hour.=20

    The current warm advection regime over eastern SD/southern MN will
    likely support periods of broken snow bands through the early
    afternoon (which appears probable based on latest reflectivity
    trends), and this may yield localized higher snowfall rates between
    1-2 inches/hour. The approach of the mid-level cold front later this
    afternoon may maintain the potential for localized banding via
    frontogenetical processes.

    ..Moore.. 12/21/2022

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7woIEW352ifqrMvcUK_isLyWjS4LdDWu0fUkpWZNXdtLYC_hZVdNthxBUJgO8BfzCmFR6zP08= A3e1sXYQ-dRUOVXRiQ$ for graphic product...

    ATTN...WFO...DLH...ARX...MPX...DMX...FSD...ABR...

    LAT...LON 45649472 45919387 45959300 45809240 45299199 44759199
    44179265 43729372 43059523 42879587 42899669 43129722
    43519746 44169712 44959611 45649472=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Aug 26 19:23:41 2023
    ACUS11 KWNS 261923
    SWOMCD
    SPC MCD 261923=20
    KYZ000-TNZ000-ILZ000-MOZ000-ARZ000-262200-

    Mesoscale Discussion 2054
    NWS Storm Prediction Center Norman OK
    0223 PM CDT Sat Aug 26 2023

    Areas affected...Parts of southern MO/IL...northern AR...western
    KY/TN

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

    Valid 261923Z - 262200Z

    Probability of Watch Issuance...40 percent

    SUMMARY...Storms capable of producing isolated to scattered damaging
    winds will become increasingly possible later this afternoon.
    Eventual watch issuance is possible for parts of the region.

    DISCUSSION...At 1915 UTC, thunderstorms are gradually increasing in
    coverage along a surface boundary from southeast MO into western KY,
    within a weakly sheared but strongly unstable environment
    characterized by MLCAPE of 2500-3500 J/kg (per recent mesoanalyses).
    Strong heating and large PW will support a threat of at least
    isolated wet microbursts as these storms sag southward through the afternoon.=20

    Farther northwest, an MCV is moving southeastward across northwest
    MO, with weak convection persisting ahead this feature across
    south-central MO. While convection directly influenced by the MCV is
    north of the surface boundary described above, a zone of clearing
    and diurnal heating/destabilization is noted from
    north-central/northwest AR into extreme south-central MO. Storms may
    intensify or redevelop as the MCV approaches this region of more
    favorable instability. If this occurs, modestly enhanced midlevel
    flow associated with the MCV may allow for somewhat organized
    clustering and upscale growth, with an attendant threat of scattered
    damaging gusts.=20

    Uncertainty remains regarding the magnitude and coverage of the
    severe threat later this afternoon, but watch issuance is possible
    if more organized convection appears imminent.

    ..Dean/Thompson.. 08/26/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!-pSnY7lHJgJP7_nApB19qLDXZ3ZSImfySkkJi1nO4-eRihlRCREcrsLM7gg6uRgMjl9x7soB4= NjH938IQJ9SEHXwpC8$ for graphic product...

    ATTN...WFO...OHX...PAH...MEG...LSX...LZK...SGF...

    LAT...LON 37019272 37709128 37768856 37578790 37328762 36868751
    36008838 35689075 35859198 35909250 36089289 36379308
    36729314 37019272=20


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