• MESO: Mesoscale Discussion 0259

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Mar 8 17:07:39 2023
    ACUS11 KWNS 081707
    SWOMCD
    SPC MCD 081707=20
    TXZ000-081930-

    Mesoscale Discussion 0259
    NWS Storm Prediction Center Norman OK
    1107 AM CST Wed Mar 08 2023

    Areas affected...portions of north central TX

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

    Valid 081707Z - 081930Z

    Probability of Watch Issuance...20 percent

    SUMMARY...A strong elevated thunderstorm is ongoing in north central
    TX. Additional storms are possible in the next couple of hours, but
    a WW is unlikely at this time.

    DISCUSSION...A strong thunderstorm is ongoing in Stephens County at
    1700z. This supercell has persisted in an environment characterized
    by around 1000 J/kg of MUCAPE and effective bulk shear around 50
    kts. The 12z FWD observed sounding and forecast RAP profiles near
    KABI/DYS suggest the most-unstable parcel resides around 1 km AGL
    with an effective inflow layer around 1-2.5 km AGL. Overlaying this
    elevated inflow layer on the current KDYX VWP yields minimal
    effective SRH. Thus, despite deep layer shear supportive of
    sustained updrafts, inflow helicity remains rather marginal.
    Radar-derived, storm-scale trends of a quasi-persistent reflectivity
    structure and more transient mid-level rotation characteristics are
    consistent with this environmental analysis.

    Some additional convective development is anticipated in the western
    portions of this MCD (additional convection initiation attempts are
    currently underway near SNK). The thermodynamic and shear profiles
    across the area are expected to remain somewhat steady for the next
    few hours as the main 500 mb trough pivots slowly over the western
    U.S. Thus, some gradual development of these cells is possible
    during the next few hours, similar to the observed evolution of the
    ongoing storm in Stephens County. Some hail is possible with these
    elevated storms, but the threat is expected to remain marginal and a
    WW is not anticipated in the short term. Some low-level warming
    (e.g., around 700 mb) is possible later in the afternoon and evening
    which may influence downstream severe hazard potential.

    ..Flournoy/Gleason.. 03/08/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!6Jxr3qCjsyilIXlRhyueJlfO5lUf0diL5tBlncclectrZY0pb_UccbQoHaxA0Ze4-kasG713-= 6V8qWZcqUnSVpsoeXo$ for graphic product...

    ATTN...WFO...FWD...OUN...SJT...LUB...MAF...

    LAT...LON 31980054 31960135 32270178 32750155 33230076 33419980
    33519863 33469775 32969744 32609791 32339886 32189970
    31980054=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Mar 15 17:28:33 2024
    ACUS11 KWNS 151728
    SWOMCD
    SPC MCD 151728=20
    TXZ000-152000-

    Mesoscale Discussion 0259
    NWS Storm Prediction Center Norman OK
    1228 PM CDT Fri Mar 15 2024

    Areas affected...Portions of south-central and southeast Texas

    Concerning...Severe potential...Watch likely=20

    Valid 151728Z - 152000Z

    Probability of Watch Issuance...80 percent

    SUMMARY...Severe storms capable of producing very large hail (2+
    inch) and severe winds are expected across portions of south-central
    and southeast Texas this afternoon. A watch will likely be issued in
    the next couple hours for parts of the area.

    DISCUSSION...Latest surface observations and visible satellite
    imagery indicate an east/west-oriented outflow-modified cold front
    gradually stalling across parts of south-central into southeast TX
    this afternoon. Given that much of this area is on the backside of a
    departing shortwave trough moving east-northeastward across east TX,
    overall coverage of storms is a bit uncertain. Nevertheless, as the
    frontal circulation intersects a gradually deepening moist layer
    amid pockets of diurnal heating, at least isolated to widely
    scattered storm development is expected this afternoon -- possibly
    aided by weak low-level warm advection atop the frontal surface/cold
    pool. An additional focus for storm development will be over the
    southern portion of the Edwards Plateau, where the front intersect
    the higher terrain amid upslope flow enhancements.

    The latest ACARS soundings from San Antonio TX sampled steep
    midlevel lapse rates (near 8 C/km) associated with an EML atop a
    gradually deepening moist layer extending through 1 km AGL.
    Continued diurnal heating of this moist layer should contribute to=20 moderate/strong instability (2500-3000 J/kg MLCAPE). In addition, a
    belt of 40-50 kt midlevel west-southwesterly flow above veering
    low-level flow will yield 40-50 kt effective shear. This will
    support the development of initially semi-discrete supercell
    clusters, capable of producing very large hail (some greater than baseball-sized), along with locally severe winds. While a tornado or
    two cannot be entirely ruled out with these storms, low-level shear
    will not be particularly strong, and the development of strong cold
    pools could reduce the risk to an extent. With time, localized
    upscale growth into several organized clusters is possible, with an
    increasing wind risk and continued large hail threat with
    east-southeastward extent.

    ..Weinman/Goss.. 03/15/2024

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!9KIjDdcIvElDc-jRF9a5kTKANV5aXMqpk6DGKqT63Y9NhWwIvu8Q_GI9HQUi1jMdM8Vo2gKCD= MhYGBsJUHgQWv7P6tA$ for graphic product...

    ATTN...WFO...LCH...HGX...CRP...EWX...

    LAT...LON 29110097 29450126 29890135 30100106 30140073 30049826
    30169736 30359635 30449568 30439523 30329461 30039456
    29589492 29139556 28829632 28699705 28639790 28609943
    28720015 28860062 29110097=20


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