• MESO: Mesoscale Discussion 2089

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Dec 31 18:48:47 2021
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    ACUS11 KWNS 311848
    SWOMCD
    SPC MCD 311848=20
    GAZ000-ALZ000-311945-

    Mesoscale Discussion 2089
    NWS Storm Prediction Center Norman OK
    1248 PM CST Fri Dec 31 2021

    Areas affected...portions of northern Alabama

    Concerning...Severe potential...Watch unlikely=20

    Valid 311848Z - 311945Z

    Probability of Watch Issuance...20 percent

    SUMMARY...Some increase in potential for a couple of severe storms
    appears to be underway, though still a conditional/uncertain
    scenario. WW remains unlikely at this point, but evolving trends
    warrant continued examination.

    DISCUSSION...Latest visible satellite imagery shows a subtle
    increase in convective activity across parts of north-central
    Alabama at this time. Though radar reflectivity remains weak,
    lightning has now been observed, and this muted convective increase
    aligns areally and temporally with persistent depiction in
    successive HRRR runs of eventual, isolated supercell development
    later this afternoon. However, the HRRR is a bit of an outlier in
    terms of coverage/intensity of afternoon convection, with only the
    hi-res ARW window even remotely supportive of the plausibility of
    the HRRR scenario.

    =46rom a synoptic perspective, weak warm advection is ongoing, near
    and north of a somewhat washed-out warm front lying across northern
    Alabama, which is supporting ongoing/weak showers across the
    southern Appalachians. Background short-wave ridging is apparent,
    which seems likely to hinder -- or at least temper -- potential for
    robust afternoon storms.=20=20

    With that said, deep-layer flow -- though a bit veered in the
    boundary layer and fairly unidirectional with height -- is
    contributing to 0-6km shear supportive of updraft rotation. As
    such, despite a larger-scale pattern that is somewhat inhibitive, we
    will continue to monitor convective evolution for signs that the
    more aggressive HRRR scenario could come to fruition -- which would
    heighten prospects for WW consideration.

    ..Goss/Grams.. 12/31/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!vnXKqz7IP2lmkDmf6vQO7yta30U1Qf4TqIjg8S9_gs44R6fln-jqtY1CTddWap2W1ORX1-FH$=
    for graphic product...

    ATTN...WFO...FFC...BMX...HUN...

    LAT...LON 33328806 33838773 34368612 34118519 33678482 33078565
    32988679 33328806=20



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