• MESO: Mesoscale Discussion 0023

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Jan 3 00:20:04 2022
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    ACUS11 KWNS 030020
    SWOMCD
    SPC MCD 030019=20
    VAZ000-TNZ000-NCZ000-KYZ000-GAZ000-ALZ000-030515-

    Mesoscale Discussion 0023
    NWS Storm Prediction Center Norman OK
    0619 PM CST Sun Jan 02 2022

    Areas affected...parts of the southern Appalachians and Southeast

    Concerning...Heavy snow=20

    Valid 030019Z - 030515Z

    SUMMARY...Periods of moderate to heavy snow will likely develop
    through this evening as temperatures begin to drop and forcing for
    ascent strengthens markedly. Snow rates of 0.5-1 in/hour will be
    possible with the strongest bands. Brief periods of mixed
    precipitation including sleet and freezing rain may also develop.

    DISCUSSION...As of 0015 UTC, a potent mid-level shortwave trough was
    analyzed via WV imagery across the eastern ARKLATEX. To the south, a
    90-100 kt jet streak was beginning to round the base of the
    positively tilted trough moving onshore across southwestern LA. A
    broad area of low pressure at the surface was centered across
    western GA with an expanding precipitation shield noted to the
    northwest of the low and ongoing convection.=20

    Recent surface observations across southwestern TN and northern MS
    have shown an increase in the occurrence of snow and mixed
    precipitation types over the last few hours with diurnal cooling
    taking place. Strong height falls from the approaching trough are
    forecast to advect eastward over the next few hours as the trough
    becomes negatively tilted, augmenting surface mass response and
    deepening the aforementioned surface low. Low-level cold advection
    should follow suit, accelerating the change over, first to mixed precipitation, and then quickly to snow of parts of the expanding
    precipitation field. While temperatures remain mild, the rain/snow
    line should move eastward with time concurrent with increasing
    precipitation rates from strengthening 850-700 frontogenesis and the development of convective bands owing to subtle buoyancy aloft.=20

    Regional soundings show favorable profiles for periods of moderate
    and occasional heavy snow expanding northeastward with time from
    northern AL into eastern/central TN along the western slopes of the
    southern Appalachians. Snow rates of 0.5 to 0.75 in/hr will be
    possible for several hours resulting in reduced visibility and
    potential travel issues. Localized 1+ in/hr rates may also be
    possible beneath the heavier convective elements or near local
    topography favorable for orographic enhancement. Snow may linger for
    a few hours overnight before forcing and dry air to the west shift precipitation northeastward.

    ..Lyons/Guyer.. 01/03/2022

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!pDf52QUVu85pb1arNbAXP7bwZ7mbvSOpWIsSoMBM34eoMpa1P6AOidgERMwzeZjzWcTX594I$=
    for graphic product...

    ATTN...WFO...GSP...MRX...JKL...FFC...OHX...BMX...HUN...

    LAT...LON 36988294 36938250 36848214 36398195 36138206 35448303
    34568481 34348622 34328700 34378746 34628792 34938800
    35328770 35628707 36328547 36988294=20



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