• Flood Risk AL/GA/TN/NC/SC

    From Mike Powell@618:250/10 to All on Fri Jul 24 09:44:20 2026
    AWUS01 KWNH 241335
    FFGMPD
    NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-241930-

    Mesoscale Precipitation Discussion 0838
    NWS Weather Prediction Center College Park MD
    934 AM EDT Fri Jul 24 2026

    Areas affected...Northern AL...Northern GA...Adj Souitheast TN,
    Western NC, Far Upstate SC...

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

    Valid 241335Z - 241930Z

    SUMMARY...Scattered, slow moving thunderstorms capable of intense
    focused heavy rainfall (2-2.5"/hr rates) support widely scattered
    incidents of possible flash flooding.

    DISCUSSION...13z surface analysis shows a weak surface wave along
    the TN/AL/GA intersection just west of Chattanooga which as arched
    the front northeastward across far SE TN before northeasterly CAD
    flow along the eastern lee of the southern Appalachians have
    anchored the front from GVL to LZU to CPP before angling
    northeastward near the Fall-line in central SC near HQU. The
    upstream portion of the front is dropping southward into northern
    AL and is denoted best in the Visible imagery with some weak
    northerly flow to help convergence south of the front.

    Tds along and west remain well into the mid-70s with some
    temperature separation from some weak early morning insolation;
    though with broad weak 10-15kts of westerly low level flow, there
    are some bubbling convective areas where MUCAPE has risen to over
    1000, nearing 1250 J/kg. Orthogonal isentropic ascent to the
    front has been the most effective in stronger and broader ascent
    with a few cells being efficient enough for a localized 2"/hr
    rate/total. However, moving off the front has resulted in
    weakening into SC, though the persistent location of the ascent is
    supportive of redevelopment and therefore increased potential of
    repeating over the next few hours.

    The increasing insolation through the morning coupled with weak
    capping should see both an increase in coverage as well as
    convective vigor, as MLCAPEs reach 1500 J/kg by late morning,
    early afternoon hours. Upstream shortwave energy will provide
    some dPVA and area (especially GA into the Carolinas will remain
    in diffluent flow aloft to support some increased
    divergence/outflow for convection. Total PWat values of 2 will
    slightly increase toward 2.25" and deep layer steering flow will
    remain slightly confluent (increasing to ~20kts) but mostly west
    to east to allow for localized repeating/training especially as
    the CAD erodes and the front lifts but remains fairly parallel to
    the mean flow. Isolated spots of 2-3.5" remain possible, but most
    should fall quickly and be in the range of the 1-3 hr FFG values
    suggestive of widely scattered to scattered incidents of
    focused/localized possible flash flooding. This would only
    increase in potential if cells can intersect the prone urban
    centers, especially Birmingham and Atlanta.

    Gallina

    ATTN...WFO...BMX...FFC...GSP...HUN...MRX...

    ATTN...RFC...ALR...ORN...NWC...

    LAT...LON 35448404 35308326 34808281 34008267 33498285
    33398363 33438491 33208708 33818794 34358802
    34658775 34858644 35398491

    $$
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    * Origin: capitolcityonline.net * KY, USA (618:250/10)