• MESO: Mesoscale Discussion 1799

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Oct 5 18:19:22 2021
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    ACUS11 KWNS 051819
    SPC MCD 051818=20

    Mesoscale Discussion 1799
    NWS Storm Prediction Center Norman OK
    0118 PM CDT Tue Oct 05 2021

    Areas affected...western/central Arizona

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

    Valid 051818Z - 052015Z

    Probability of Watch Issuance...95 percent

    SUMMARY...Ahead of the upper low, widespread thunderstorms will
    likely organize this afternoon/evening. Damaging winds and large
    hail appear likely though a tornado may also be possible with any
    supercells. While uncertainty on the best temporal window for severe
    remains, a weather watch is likely within the hour.

    DISCUSSION...As of 1800 UTC, regional radar showed scattered to
    widespread thunderstorms ongoing across much of central and western
    AZ into southern NV. Ongoing in broad ascent ahead of an upper low
    ejecting out of southern California, additional storm development
    appears likely over the next couple hours. Visible imagery shows
    breaks in the clouds are supporting modest surface
    heating/destabilization with 500-1000 J/kg of MLCAPE on SPC
    mesoanalysis. Deep southerly flow aloft around 40 kts will be
    sufficient to support organized storms, including a few supercells,
    with bulk shear of 40-50 kts. Low-level shear remains weaker, but
    low-level backing of the flow ahead of the upper low may support a
    brief tornado or two along with the relatively greater threat for
    strong wind gusts and large hail. The steep low and mid-level lapse
    rates may also support a few significant gusts or hail greater than
    2+ in as well.

    Convective trends and hi-res guidance point to the increase severe
    potential across western and central AZ in the next couple of hours
    as the ongoing cluster of storms from southern NV, eastern CA and
    western AZ move northeast. Some uncertainty exists on the convective
    evolution of the northern cluster as it approaches an area of lesser
    buoyancy under more persistent cloud cover across north-central AZ.
    Additional thunderstorms developing within cloud breaks farther to
    the south and west will likely have the greatest severe potential as
    they track into central AZ over the next few hours. Given the
    increasing threat for damaging wind gusts hail and perhaps a
    tornado, a weather watch is likely.

    ..Lyons/Guyer.. 10/05/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!uNU2rtUa6w5ZGT2sDg7IUuUBfdbT4ulo4yXHHrCFUBy82BTFZtkUDM-vHR3C3_ExLWUyS55w$=
    for graphic product...


    LAT...LON 32761218 32661318 32721359 32921385 33251401 33541413
    34131407 34531421 35451475 36011458 36431414 36591339
    36411256 36101177 35671140 34861113 34261092 33691081
    33311076 33041090 32871161 32761218=20

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