Mesoscale Precipitation Discussion 0978
NWS Weather Prediction Center College Park MD
121 PM EDT Thu Sep 05 2024
Areas affected...southern Louisiana, coastal areas of Mississippi
Concerning...Heavy rainfall...Flash flooding likely
Valid 051720Z - 052320Z
Summary...Flash flood potential continues especially across
southern Louisiana, where scattered thunderstorms continue to
migrate slowly northwestward ahead of a low over the Gulf of
Mexico.
Discussion...Scattered to widespread convection has organized into
a 1) dominant banded structure extending from near Baton Rouge
east-southeastward through Slidell to the Chandeleur Islands east
of New Orleans, and 2) scattered, but more widespread convection
extending from a low centered south of Galveston eastward to the
mouth of the Mississippi River. Many areas of 1-2.5 inch/hr rain
rates have been observed beneath the heavier bands - all supported
by slow movement and abundant moisture/buoyancy especially nearer
the coastal areas.
Much of the stronger/deeper convection has been focused in areas
of closer access to stronger instability (1000+ J/kg MLCAPE).
These areas are also closer to the warmer Gulf of Mexico, with
warm SSTs aiding in maintenance of 76-80F dewpoints that are
supporting that instability. These trends are likely to continue
through the evening, with slow-moving convection continuing to
drift northward across southern Louisiana (including areas near
Lake Pontchartrain) and adjacent areas of coastal Mississippi.
1-2.5 inch/hr rain rates and three-hourly rates exceeding 3 inches
are both supportive of flash flooding - especially in typical
sensitive/urbanized locales. Models suggest that convection will
likely persist beyond 23Z/6p CST - especially near coastal areas
where greater instability will persist. Scattered instances of
flash flooding are expected, and significant impacts might occur
especially if heavier rain rates can occur in populated areas
in/near Baton Rouge and New Orleans.
Cook
ATTN...WFO...LCH...LIX...MOB...
ATTN...RFC...LMRFC...WGRFC...NWC...
LAT...LON 30999074 30918987 30768908 30578849 30238842
29578870 29108901 28858956 29019121 29399260
29619366 30249357 30459283 30579180 30789125
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