Mesoscale Precipitation Discussion 158
NWS Weather Prediction Center College Park MD
621 PM EDT Tue Apr 22 2025

Areas affected...Southern LA...Southern MS...West central AL

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

Valid 222221Z - 230300Z

Summary...Scattered to numerous slow moving thunderstorms, some
with rainfall rates exceeding two inches per hour, are likely to
continue through the evening hours. Some instances of flash
flooding will be possible where cells become most persistent.

Discussion...Convection continues to develop and persist south of
a weak, stalling surface front and wave of low pressure. Regional
Doppler radars are indicating multi-cellular clusters with some
back-building convection, with the most impressive radar
signatures just north of the Interstate 10 corridor in
south-central Louisiana, and a second area slow dropping south
near the MS/AL border. Enhanced-V signatures on GOES visible and
infrared satellite is also apparent, and thus evidence that these
cells are becoming anchored in place for an hour or more in some
cases. MRMS rainfall estimates of 2+ inches per hour have been
observed, and although flash flood guidance values are generally
high across most of the outlook area, this could be enough to
cause some flooding issues in poor drainage and urban areas.

The latest CAM guidance suite generally agrees on the idea of
scattered QPF maxima of 2-4 inches through 10 pm local time, with
most of this falling within a two-hour time period in any given
location. HREF exceedance probabilities of flash flood guidance
are relatively low, but probably higher in reality given what is
currently happening. Once these multi-cell clusters become more
outflow dominant later this evening, the flooding threat with
these cells should diminish.

Hamrick

ATTN...WFO...BMX...JAN...LCH...LIX...MOB...SHV...

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

LAT...LON   33228908 33228842 32648804 31418847 30768898
            30518954 30469060 30209165 30189221 30369306
            30969371 31529342 31779267 31849210 31879112
            32239035 32718970