• MESO: Mesoscale Discussion 0652

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wednesday, June 06, 2018 19:23:10
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    ACUS11 KWNS 061923
    SWOMCD
    SPC MCD 061922
    IAZ000-MOZ000-NEZ000-SDZ000-062115-

    Mesoscale Discussion 0652
    NWS Storm Prediction Center Norman OK
    0222 PM CDT Wed Jun 06 2018

    Areas affected...Portions of the mid Missouri Valley

    Concerning...Severe potential...Watch possible

    Valid 061922Z - 062115Z

    Probability of Watch Issuance...60 percent

    SUMMARY...Scattered thunderstorms are expected to develop by late
    afternoon, with an attendant threat of damaging winds and large
    hail. A watch may be needed within the next 1-2 hours.

    DISCUSSION...Visible satellite and surface analysis data indicate a
    somewhat complex pattern across the region this afternoon. A
    well-defined surface trough stretches from northeastern Colorado to
    a weak low over northeastern Nebraska, and then onward to northern
    Iowa. To the south of this trough, observations indicate a prior
    outflow boundary has mixed out across Iowa, yielding a quickly
    destabilizing boundary layer from western Iowa into south-central
    and eastern Nebraska. Along with temperatures rising into the lower
    90s, dew points in the upper 60s/lower 70s are yielding MLCAPE
    values upwards of 4000 J/kg (based on meso-analysis data) south of
    the trough. The 12Z OAX sounding, adjusted for current surface
    conditions, confirms this level of strong instability.

    Although forcing for ascent aloft remains nebulous, radar/satellite
    data highlight an MCV over north-central Kansas, and this could
    support convective initiation across parts of southern Nebraska, as
    it continues to slide east/northeast. More probable, however, is the development of organized convection over eastern Nebraska into Iowa,
    as weak mid-level ascent northeast of the MCV overspreads a
    low-level theta-e/instability maximum near the Missouri Valley.

    Although effective shear and flow through 500mb remain modest at
    best (i.e., no more than 20-25 kt), very unstable profiles will
    favor strong downdraft momentum and a damaging wind threat. Large
    hail will also be possible, but aforementioned modest flow may
    temper the threat for very large hail growth. Into early evening,
    cells will likely propagate southward into the instability axis,
    with some upscale growth maintaining a damaging wind threat. To
    account for this threat, a watch may be needed within the next 1-2
    hours.

    ..Picca/Weiss.. 06/06/2018

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

    ATTN...WFO...DMX...EAX...FSD...OAX...GID...LBF...

    LAT...LON 40399837 40849857 41349855 42039817 42549686 42769598
    42749506 42119364 41609264 41349251 40819271 40399441
    40169542 40099618 40129775 40219809 40399837



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