AWUS01 KWNH 100854
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-101452-

Mesoscale Precipitation Discussion 1238
NWS Weather Prediction Center College Park MD
453 AM EDT Thu Sep 10 2026

Areas affected...Central Gulf Coast

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

Valid 100852Z - 101452Z

Summary...Showers and thunderstorms are forming near and offshore
the coasts of southeast LA, MS, AL, and the western FL Panhandle. 
Hourly rain amounts to 3" could lead to isolated to widely
scattered flash flooding, primarily in urban areas.

Discussion...An upper level low was spotted on GOES-19 imagery
offshore Galveston TX, while an upper level shear line was
apparent over southernmost AL and southern MS.  A surface
circulation was apparent in the oil rig observations to the
south-southeast of Galliano LA.  CIN has been eroding across the
region over the past several hours.  Precipitable water values are
2-2.2" per GPS data.  The Central Gulf Coast lies in an
instability gradient north of the warm Gulf, with an ML CAPE
bubble of 3000 J/kg offshore southeast LA.  Effective bulk shear
of 25 kts is not far away to the northwest of Lake Pontchartrain.

A zone of 850 hPa confluence is expected to remain near the
Central Gulf Coast over the next six hours.  The mesoscale
guidance signal for heavy rain shifts westward from near
Pensacola, where some thunderstorms recently went inland, along
the AL and MS coasts to Southeast LA by 11z.  Thunderstorms moving
inland should sharpen the instability gradient to the immediate
coast/swamp margin over time.  Hourly rain amounts to 3" are
possible where cells merge or manage to train.  Urban areas would
be most sensitive to the incoming heavy rainfall.  Flash flooding
instances are expected to be isolated to widely scattered.

Roth

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

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

LAT...LON   30958862 30958706 30358630 30098779 30068855 
            29568890 29318895 28878902 28958941 29188970 
            29009032 29169040 29089078 29239121 30109076 
            30539017 

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