• MESO: Mesoscale Discussion 1418

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Aug 3 20:26:46 2021
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    ACUS11 KWNS 032026
    SWOMCD
    SPC MCD 032026=20
    IDZ000-ORZ000-WAZ000-032300-

    Mesoscale Discussion 1418
    NWS Storm Prediction Center Norman OK
    0326 PM CDT Tue Aug 03 2021

    Areas affected...portions of eastern Oregon into far west-southwest
    Idaho

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

    Valid 032026Z - 032300Z

    Probability of Watch Issuance...5 percent

    SUMMARY...A damaging gust or brief instance of marginally severe
    hail is possible over the next few hours as storms increase in
    coverage and intensity. The severe threat is expected to be sparse,
    and a WW issuance is not expected.

    DISCUSSION...High-based, pulse-cellular storms have recently
    initiated across far southeast OR (per latest MRMS mosaic radar
    data), with visible satellite imagery showing a developing CU field
    across northeast OR. With continued heating/boundary-layer mixing,
    storms are expected to increase somewhat in coverage and intensity
    across eastern OR into western ID through the afternoon. Latest
    METAR observations show temperatures exceeding 90F across eastern
    OR, with dewpoints in the upper 40s, yielding a 40+ F
    temperature/dewpoint spread in a few spots, indicative of a
    well-mixed boundary layer already in place. 18Z RAP forecast
    soundings for the 20-22Z period suggest that the boundary layer
    extends above 600 mb, with 0-3km lapse rates reaching 10 C/km.=20

    The very steep low-level lapse rates and deep, dry boundary layer
    will foster the potential for a couple damaging gusts with the
    heavier storm cores. In addition, with 8+ C/km mid-level lapse rates
    in place, a severe hailstone or two cannot be ruled out with the
    strongest updrafts, especially if a transient supercell structure
    develops. However, marginal instability (500-1000 J/kg MLCAPE) amid
    poor deep-layer shear suggests that any severe wind/hail threat that
    develops will be quite sparse and short-lived, and the issuance of a
    Severe Thunderstorm Watch appears unlikely.

    ..Squitieri/Grams.. 08/03/2021

    ...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!vU6LRbBe-99WppYdyS832b_VWkcdYhDcHf5osf_zQZvCLF31kQ7eE6gcS_y4fVPt3TpIjoiN$=
    for graphic product...

    ATTN...WFO...MSO...BOI...OTX...PDT...MFR...

    LAT...LON 42041926 42531961 43381983 44241956 45171907 46051829
    45971720 45581664 44711627 44031615 43691613 42921616
    42481638 42021690 42041926=20



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