• MESO: Mesoscale Discussion 1658

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sunday, November 25, 2018 10:55:23
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    ACUS11 KWNS 250955
    SWOMCD
    SPC MCD 250954
    IAZ000-MOZ000-KSZ000-NEZ000-251600-

    Mesoscale Discussion 1658
    NWS Storm Prediction Center Norman OK
    0354 AM CST Sun Nov 25 2018

    Areas affected...Central...north-central and northeast
    KS...southeast NE...southwest IA...and northwest MO

    Concerning...Heavy snow

    Valid 250954Z - 251600Z

    SUMMARY...Snowfall rates up to 1-2 inches per hour will increase
    from west to east during the late overnight through this morning.
    In addition to heavy snow, strengthening northerly winds through the
    morning will produce a blizzard with reduced visibilities in
    whiteout conditions.

    DISCUSSION...Short-term guidance remains consistent with the
    forecast for a vigorous shortwave trough, now located over eastern
    CO, to emerge eastward across KS overnight, with deepening of this
    system between 12-18Z as it reaches eastern KS/western MO by late
    morning. Trends in mosaic radar imagery showed a band of
    precipitation had developed from north-central KS to southeast NE.
    This corridor in the northern part of the discussion area is
    expected to be the first southwest-northeast oriented zone to change
    to snow and increase in rates as surface temperatures fall through
    the lower 30s to upper 20s F by 11-12Z. This same trend with snow
    developing across the rest of the discussion area after daybreak
    from central to northeast KS and far northwest MO to southwest IA
    will occur as the surface low shifts east-northeast into MO. This
    will allow low-level winds on its north-northwest periphery to back
    to northerly and strengthen, ushering in colder temperatures, and
    supporting a high likelihood for reduced visibilities in whiteout
    conditions.

    Meanwhile, an increase in upward vertical motion through the
    dendritic-growth zone per forecast soundings is expected as, 1) the
    shortwave trough deepens with eastward progression and 2) within the
    exit region of a strengthening 500-mb 100-kt jet spreading across
    northeast KS/northwest MO this morning. This factor which is
    expected to become stronger by 15-18Z suggests snowfall rates could
    be up to 2 inches per hour, generally north of a line from KSLN to
    KSTJ to 25 S KLWD, while the initial aforementioned band of snow
    could have rates up to 1 inch per hour. Forecast soundings also
    indicated weak elevated instability rooted around 600 mb, given the
    likelihood of steepening midlevel lapse rates (around 8 C/km) in the
    exit region of the midlevel jet. This could enhance snowfall rates.

    ..Peters.. 11/25/2018

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

    ATTN...WFO...DMX...EAX...OAX...TOP...ICT...GID...DDC...GLD...

    LAT...LON 41259537 41359315 41159252 40309380 39249539 38409689
    38239774 38379854 38699916 38909976 39289995 39479979
    40099877 40489775 40979632 41259537



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