• MESO: Mesoscale Discussion 1621

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Monday, November 05, 2018 22:39:15
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    ACUS11 KWNS 052139
    SWOMCD
    SPC MCD 052138
    MSZ000-TNZ000-ARZ000-LAZ000-052345-

    Mesoscale Discussion 1621
    NWS Storm Prediction Center Norman OK
    0338 PM CST Mon Nov 05 2018

    Areas affected...northern Louisiana...eastern Arkansas...northern
    Mississippi and western Tennessee

    Concerning...Severe potential...Watch likely

    Valid 052138Z - 052345Z

    Probability of Watch Issuance...80 percent

    SUMMARY...Storms are expected to increase in coverage mainly after
    23-00Z across northern Louisiana and eastern Arkansas, and will gain
    strength as they develop eastward into northern Mississippi and
    Tennessee during the evening. Damaging winds and tornadoes will be
    possible.

    DISCUSSION...The air mass across east TX and the lower MS Valley
    continues to destabilize via both low-level theta-e advection
    associated with a warm front, and mixing of the boundary layer aided
    by pockets of heating. As of 21Z, the most unstable air was located
    over southeast TX, where 70s F dewpoints and strong heating exist.

    18Z soundings indicate a substantial midlevel inversion which is
    limiting instability. This inversion will weaken somewhat this
    evening as a strong jet max noses into AR, northern MS and western
    TN, providing cooling aloft.

    Currently, scattered convective showers exist near the instability
    axis over east TX and northwest LA, but they are shallow with no
    lightning due to the warm midlevel temperatures. However, they are
    already rotating. Farther north, a band of ascent was evident on
    radar from the ArkLaTex into central AR, with gradually warming
    temperatures south of that area.

    Over the next several hours, both these areas will likely
    consolidate into thunderstorms across northern LA and southern AR,
    and may mature into northern MS and western TN this evening. Shear
    profiles will continue to increase as the low-level jet intensifies
    to over 50 kt. Hodographs will strongly favor supercells,
    potentially tornadic, but storms may eventually transition to a
    QLCS. Therefore, both damaging winds and tornadoes will be possible.
    The greatest threat is likely to exist east of the MS river and
    after 03Z, when lift, shear, and low-level moisture are maximized.

    ..Jewell/Thompson.. 11/05/2018

    ...Please see www.spc.noaa.gov for graphic product...

    ATTN...WFO...MEG...JAN...LZK...SHV...

    LAT...LON 32719056 32259196 31919297 31779346 31789375 32059397
    32339384 34239146 34999072 35349027 35538956 35448887
    35128851 34618835 34378839 33368946 32719056



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