528
AWUS01 KWNH 120228
FFGMPD
FLZ000-GAZ000-ALZ000-MSZ000-LAZ000-120730-

Mesoscale Precipitation Discussion 0171
NWS Weather Prediction Center College Park MD
1027 PM EDT Mon May 11 2026

Areas affected...central/east-central Gulf Coast

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

Valid 120226Z - 120730Z

Summary...Heavy rain with embedded thunderstorms are expected
along portions of the central to east-central Gulf Coast through
07Z. Isolated flash flooding will remain possible due to hourly
rainfall of 2 to 3+ inches and localized totals of 3 to 5+ inches.

Discussion...Heavy rain remained in a few locations over
southeastern LA as of 02Z with a small cluster of largely
warm-topped showers/thunderstorms southwest of Lake Pontchartrain
with MRMS-derived peak hourly rainfall between 2 and 3 inches. The
00Z LIX sounding showed a moist environment with at PW of 1.9
inches and only 5 kt of 0-6 km mean layer flow, supportive of slow
cell movement. Instability was weak, however, with only 280 J/kg
MLCAPE on the LIX sounding. Over the past hour, there has been
some eastward development of localized heavy rain cores through
southern MS/AL and the western FL Panhandle. These appear to be
focused along a low level axis of convergence, just above the
surface, represented in 925 mb VAD wind plots, extending from near
Lake Pontchartrain into the FL Panhandle. Aloft, a potent mid to
upper-level shortwave was noted on water vapor imagery just east
of the Sabine River. Divergent flow aloft was focused just ahead
of the shortwave and associated jet axis across southeastern LA
into southern MS, aiding lift over the region.

As the shortwave continues to move east tonight, ascent will
translate downstream along the Gulf Coast, with embedded areas of
heavy rain likely following suit. Given the moist environment (PWs
of 1.6 to 1.9 inches), with warm-layer depths of 3500-4000 m,
efficient rainfall will be likely with hourly rainfall of 2 to 3+
inches at times and possibly 3 to 5 inches within a 2-3 hour
period. While weak instability (less than 1000 J/kg) will limit
the coverage of heavy rain, small pockets of flash flood potential
will remain a possibility over at least the next 3-5 hours.
Another consideration is the higher than average rainfall over the
past 1-2 weeks across a good portion of the region which may leave
locations more prone to runoff compared to average.

Otto

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...JAN...LIX...MOB...TAE...

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

LAT...LON   31538685 31348491 30798405 30038420 29538512
            29508610 29818860 29668986 29589045 29829090
            30359093 30979028 31238915