• MESO: Mesoscale Discussion 1876

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Oct 19 17:23:06 2021
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    ACUS11 KWNS 191723
    SPC MCD 191722=20

    Mesoscale Discussion 1876
    NWS Storm Prediction Center Norman OK
    1222 PM CDT Tue Oct 19 2021

    Areas affected...portions of eastern/central Wyoming

    Concerning...Heavy snow=20

    Valid 191722Z - 192115Z

    SUMMARY...Ongoing moderate to heavy precipitation will gradually
    transition to snow this afternoon across central and eastern WY
    impacting travel conditions. Snow rates above 1 inch per hour with
    occasional reductions in visibility due to heavy and blowing snow
    are possible.

    DISCUSSION...As of 1700 UTC, WV imagery showed the core of a
    well-defined upper low was located near the western CO, UT and WY
    borders. To the north and east of the upper low, large-scale forced
    ascent was supporting the development of widespread stratiform
    precipitation across much of western and central Wyoming.=20

    Over the last hour, regional radar imagery showed additional banded precipitation developing ahead of the low from the vicinity of KRIW
    to KLAR. Likely in response to increasing lift near a region of
    strong 700 mb frontogenesis, as well as orographic ascent,
    additional precipitation development/intensification within this
    band appears likely over the next several hours. Surface
    temperatures across much of Wyoming remain just above freezing
    suggesting initial precip type will be rain below 7k feet. However,
    as column saturation takes place, dynamic cooling and increasing
    low-level cold advection from surface pressure falls ahead of the
    upper low should result in a transition to snow by early afternoon.=20

    As the upper low continues eastward along the CO/WY border, strong
    height falls (60-90 DM/12 hr) should support moderate to heavy snow
    within the developing frontogenetic band as it wraps
    north/northwestward around the low. Hi-res guidance and regional
    model soundings show support for snow rates near or exceeding 1 inch
    per hour through the afternoon driven in part by steep mid-level
    lapse rates near the cold core of the upper low. Additionally, weak
    convective buoyancy as well as negative EPV (indicative of
    slant-wise instability) suggest some potential for convective
    elements/banding favorable for locally higher snow rates through the
    afternoon. While the transition from rain to snow is likely to be
    gradual, moderate to heavy snow appears likely across much of
    central and eastern Wyoming through the afternoon. The potential for
    heavy snow and gusty north winds may result in occasional blowing
    snow/low visibility disruptive to travel. Weakening ascent and
    increasingly dry mid-level air should end the heavy snow threat as
    the upper low shifts to the northeast this evening.

    ..Lyons/Bunting.. 10/19/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!sJ7uJWczCX5UYne0G8ApJWmMXJTvPMgsLn5cSFqWEKo6cbaA-s514T1icxQXztOGkD4aDBlg$=
    for graphic product...


    LAT...LON 43590504 43330483 42870478 42530471 42240473 41850484
    41670516 41580560 41700621 42100671 42460760 42580804
    42860833 43260838 43730775 43820720 43810640 43790598

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