• Heavy Rain/Flooding SE US

    From Mike Powell@618:250/1 to All on Sat Sep 14 08:49:00 2024
    AWUS01 KWNH 141001
    FFGMPD
    GAZ000-TNZ000-ALZ000-MSZ000-141600-

    Mesoscale Precipitation Discussion 1007
    NWS Weather Prediction Center College Park MD
    600 AM EDT Sat Sep 14 2024

    Areas affected...Western and Middle TN...Far Northeast
    MS...Northwest to Southeast AL...Southwest to Central GA

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

    Valid 141000Z - 141600Z

    SUMMARY...Locally slow-moving and occasionally training bands of
    heavy showers and thunderstorms is expected to maintain a threat
    for some areas of flash flooding going through the morning hours.

    DISCUSSION...Generally there has not been much change over the
    last several hours to setup and character of the heavy rainfall
    threat that continues to impact areas of the Mid-South. The latest
    GOES-E IR satellite imagery coupled with dual-pol radar continues
    to show some broken bands of showers and occasionally some
    thunderstorms across portions of western and middle TN down
    through much of northwest and central AL. Some weaker and more
    disorganized convection is seen over parts of southeast AL. This
    is all in association with what is left of Post-T.C. Francine.

    There continues to be an axis of persistent moisture convergence
    and modest instability oriented in a north-northwest to
    south-southeast fashion across the region, with MUCAPE values of
    500 to 1000 J/kg and PWs of 1.75 to 2.0 inches. A very gradual
    cyclonic pivoting of the convection has been occurring over the
    last few hours as the ill-defined center of Post-T.C. Francine and
    its frontal occlusion tends to lose latitude.

    Going through the morning hours, some additional focus for broken
    bands of convection should continue with some additional
    likelihood for some cell-training. This will be favored by a
    persistent fetch of at least modest moisture transport and
    instability around the eastern flank of the weakening frontal
    occlusion. Rainfall rates with the stronger convective cores may
    reach 1 to 1.5 inches/hour this morning and this is consistent
    with the 00Z/06Z HREF guidance. Recent HRRR runs suggest that
    there could be some potential for convection to develop and
    perhaps become locally a bit more concentrated farther down to the
    south and east across areas of southeast AL and into parts of
    southwest to central GA but there is more model spread overall
    with the details of this.

    Some additional spotty rainfall totals this morning of 2 to 4
    inches will be possible where any additional cell-training occurs,
    and given the wet antecedent conditions across most of the region,
    this may foster some additional runoff concerns and possible flash
    flooding.

    Orrison

    ATTN...WFO...BMX...FFC...HUN...JAX...MEG...MOB...OHX...TAE...

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

    LAT...LON 36188789 35748724 34788633 33388506 32428274
    31608259 31058344 31118518 31668619 33158712
    34088787 34928893 35558908 36138869
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