AWUS01 KWNH 111446
FFGMPD
MSZ000-LAZ000-112040-

Mesoscale Precipitation Discussion 0988
NWS Weather Prediction Center College Park MD
1044 AM EDT Wed Sep 11 2024

Areas affected...southern LA/MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 111442Z - 112040Z

Summary...At least localized areas of flash flooding will become
likely through 21Z across southeastern LA into coastal MS.
Repeating and training of cells will produce 1 to 3 in/hr rainfall
rates along with localized 6 hour totals possibly exceeding 4
inches.

Discussion...14Z infrared satellite imagery showed the CDO
associated with Hurricane Francine located ~100 miles south of the
western LA coast along with a secondary area of cold cloud tops
over south-central and southeastern LA. The secondary area of
colder cloud tops was located along and north of a slow moving
warm front analyzed eastward from the southeastern LA coast into
the north-central FL Peninsula. Trends in radar imagery over the
past 1-2 hours have shown an increase in the number of showers and
thunderstorms located from Lake Pontchartrain to ~75 miles south
of Mobile Bay. These showers and thunderstorms were co-located
with an axis of low level convergence near the front where
precipitable water values near 2.5 inches will be capable of
efficient rainfall production. SPC mesoanalysis data showed MLCAPE
of 500 to 1000+ J/kg over southern LA with a notch of higher
instability pointed into the MS River Delta and Chandeleur Sound.

Convergent southeasterly low level flow is forecast to remain in
place near the slow moving warm front over southeastern LA and
just south of the MS coast where mean steering flow will allow for
a repeating nature to cells along with some training from the
south to southeast containing rainfall rates of 1 to 3 in/hr.
Farther west, as Francine continues to approach the south-central
LA coast, increasing steady rainfall will become heavier with
rainfall rates of 1-2 in/hr becoming more likely and frequent
across central LA coastal sections through the mid-afternoon.

While expected to remain localized, at least through 20Z, areas of
flash flooding are expected to become likely into the afternoon.
Wet antecedent ground conditions from heavy rain over the past
week are expected to contribute to an increased flash flood risk.

Otto

ATTN...WFO...LCH...LIX...

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

LAT...LON   30549012 30378872 30188845 29538827 29058843 
            28698925 28669005 28799101 29309160 29509240 
            30289234 30539137 
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