• MESO: Mesoscale Discussion 0212

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Mar 1 09:34:42 2023
    ACUS11 KWNS 010934
    SWOMCD
    SPC MCD 010934=20
    CAZ000-011330-

    Mesoscale Discussion 0212
    NWS Storm Prediction Center Norman OK
    0334 AM CST Wed Mar 01 2023

    Areas affected...the San Gabriel...San Bernardino and San Jacinto
    Mountains vicinity

    Concerning...Heavy snow=20

    Valid 010934Z - 011330Z

    SUMMARY...Heavy snow is expected to continue developing across the
    higher terrain through daybreak, with rates peaking up to 2-4 inches
    per hour across parts of the San Bernardino into San Jacinto
    Mountains around 4-7 AM PST.

    DISCUSSION...Deepening mid-level troughing, with a developing
    embedded low, continues to dig inland of the Pacific coast, with the
    exit region of an intense jet streak (in excess of 110 kt around 500
    mb) still offshore of the coast nosing toward the LA Basin through
    daybreak. Aided by increasing forcing for ascent, likely largely
    still due to low-level warm advection, moderate to locally heavy
    precipitation has already been overspreading much of southern
    California coastal areas into the western slopes of the adjacent
    mountains.

    Forecast soundings suggest that the dendritic growth layer, which is
    roughly centered near or below the 600 mb level, remains
    unsaturated. However, with continuing mid-level height falls and
    strengthening divergence aloft this is forecast to change during the
    next few hours. As west-southwesterly flow in the 4000-8000+ foot
    layer strengthens to 40-50+ kt, increasing orographic forcing for
    ascent on the windward-facing mountain slopes is expected to
    contribute to intensify snow rates, in the presence of precipitable
    water increasing in excess of .60 inches. Rapid Refresh forecast
    soundings and High Resolution Ensemble output suggest snow rates may
    maximize on the order of 2-4 inches per hour in the 12-15Z time
    frame across the San Bernardino into San Jacinto Mountains. During
    this time, freezing levels across lower elevations may slowly rise
    toward 5000 ft, before falling again later this morning. However,
    due to the heavy snow rates, and cooling due to melting, snow levels
    might be maintained at 3500-4000 feet.

    ..Kerr.. 03/01/2023

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!8CcvjlDMjiRQEPFeYExvWjELVvkLIIBb7NjUh-fXN7pqUAaENmRWevtndlLSBGIjKsidT4YVw= tRwtMvGP-TrrUDzKnI$ for graphic product...

    ATTN...WFO...PSR...VEF...SGX...LOX...

    LAT...LON 34371772 34191642 33381625 33161651 33421680 33991699
    34371772=20


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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Mar 9 18:53:32 2024
    ACUS11 KWNS 091853
    SWOMCD
    SPC MCD 091852=20
    GAZ000-FLZ000-092015-

    Mesoscale Discussion 0212
    NWS Storm Prediction Center Norman OK
    1252 PM CST Sat Mar 09 2024

    Areas affected...North FL into southeast GA

    Concerning...Tornado Watch 34...

    Valid 091852Z - 092015Z

    The severe weather threat for Tornado Watch 34 continues.

    SUMMARY...Some threat for locally damaging gusts and a tornado or
    two may continue through the afternoon. Local extension of WW 34 may
    be needed.

    DISCUSSION...A broken line of storms with embedded supercell
    structures is ongoing at 1845 UTC from southeast GA into north FL.
    While some gradual veering of low-level flow has been noted with
    time, moderate buoyancy (MLCAPE of 1000-1500 J/kg) and rather strong
    low-level (with 0-1 km SRH of 150-250 m2/s2) and deep-layer shear
    continue to be supportive of organized convection. Occasional
    embedded supercell structures continue to be noted, and some threat
    for a tornado or two may persist through much of the afternoon,
    especially with the supercell currently over Brantley County, GA.
    Otherwise, locally damaging gusts will remain possible with the
    strongest storms, especially in areas where stronger heating and
    steepening of low-level lapse rates have been observed.=20

    While an eventual weakening trend is expected as stronger
    large-scale ascent moves away from the region, some severe threat
    will persist beyond the 2 PM EST expiration time of WW 34. As a
    result, local watch extension may be needed to address the threat
    through late afternoon.

    ..Dean/Smith.. 03/09/2024

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!7d5J7Jj9e0NKcARXYuseWUAC4SYBEUSrol__QTFK_i0JIhI3miND1lBKMrMz17o6tUOgGiviy= s19OHFpNcXuy4r9VFY$ for graphic product...

    ATTN...WFO...CHS...JAX...TAE...

    LAT...LON 30128145 29828355 30028400 30408380 30538369 31468191
    31778134 31698121 31108123 30608129 30128145=20


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