• Heavy Rain/Flooding AL/GA

    From Dumas Walker@21:1/175 to All on Fri Sep 13 08:25:00 2024
    AWUS01 KWNH 131006
    FFGMPD
    GAZ000-ALZ000-131530-

    Mesoscale Precipitation Discussion 1001
    NWS Weather Prediction Center College Park MD
    606 AM EDT Fri Sep 13 2024

    Areas affected...Portions of Eastern AL...Western GA

    Concerning...Heavy rainfall...Flash flooding possible

    Valid 131005Z - 131530Z

    SUMMARY...Broken areas of heavy showers and thunderstorms may
    support an isolated threat of flash flooding this morning.

    DISCUSSION...The latest GOES-E WV satellite imagery in conjunction
    with dual-pol radar shows a broken cluster of heavy showers and
    thunderstorms lifting northeastward up across portions of eastern
    AL which will likely spread into areas of western GA early this
    morning. The convection which is relatively warm-topped in nature
    is being driven by a modest shortwave ejecting across southeast AL
    while interacting with a generally north-northwest to
    south-southeast axis of moisture convergence and modest
    instability near a quasi-stationary front.

    Broad and moist, confluent low-level flow is noted across much of
    the central Gulf Coast region as Post-Tropical Cyclone Francine
    continues to move slowly across areas of eastern AR and bumps up
    against surface high pressure nosing well south into the interior
    of the Southeast. The instability axis is characterized by MUCAPE
    values of 500 to 1000 J/kg across central and southern AL over
    into portions of west-central GA.

    Quite a bit of mid to upper-level dry air is showing up in the WV
    satellite imagery along with CIRA-ALPW data in the 500/300 mb
    layer which is helping to limit/cap the vertical extent of
    convective development, but there is sufficient forcing and
    moisture noted below 500 mb to favor relatively efficient and
    warm-topped convection with rainfall rates of 1 to 2 inches/hour.

    The overnight HREF guidance and recent HRRR runs have a poor
    handling of the ongoing activity, but satellite trends suggest
    some increasing trends toward heavier rainfall rates with some
    cloud-top cooling. This suggests a corridor of stronger forcing
    which is also aligned with the aforementioned moisture convergence
    and instability axis.

    Some occasional backbuilding of the broken complex of convection
    will be possible this morning which may allow for sufficient
    persistence of heavier rainfall rates to support some spotty
    totals of 2 to 4+ inches. This may result in an isolated threat of
    flash flooding which would likely be primarily a threat to the
    more sensitive urban environments.

    Orrison

    ATTN...WFO...BMX...FFC...

    ATTN...RFC...SERFC...NWC...

    LAT...LON 34008543 33428462 32908433 32278429 31988470
    32058531 32738566 33668607
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