From Mike Powell@618:250/1 to All on Sat Aug 2 18:20:47 2025
AWUS01 KWNH 021937
FFGMPD
MSZ000-LAZ000-030100-
Mesoscale Precipitation Discussion 0853
NWS Weather Prediction Center College Park MD
336 PM EDT Sat Aug 02 2025
Areas affected...Central Louisiana...
Concerning...Heavy rainfall...Flash flooding possible
Valid 021935Z - 030100Z
SUMMARY...Slow moving, efficient thunderstorms with potential of
favorable propagation for some repeating/training. Rates of
2-2.5"/hr and localized totals of 3-4" may result in localized
rapid inundation flooding.
DISCUSSION...GOES-E WV suite shows a weak/elongated shortwave
feature along the southwest edge of the northern stream troughing
across southwest AR into northeast Texas. This places the feature
in the northeast quadrant of the synoptic ridge over TX and so
flow becomes highly diffluent and weaker across central LA.
Combine this with the mixed/worked over area affected by the
complex across E TX this morning; there is a solid area of
remaining high moisture/unstable air across much of LA into SW MS
with total PWat values of 2.2-2.4 AND SBCAPEs over 2500-3000 J/kg
for stronger, efficient thunderstorm development. This will
support cells capable of intense instantaneous rates with
localized 2-2.5"/hr totals scattered with the most intense cores
to convection (as noted with initial round in north-central LA).
Deep layer flow is weak and convergence is going to be generally
driven by convective outflow propagation. As such, the older
outflow boundary across E TX is also along/parallel to the deeper
layer steering into the col east of the upper-level ridge.
Initial convective development toward the northeast also helps to
corral newer development along the I-49 corridor and should
support slow but repeating environment to add overall totals
toward the generally higher FFG values across the region. Given
upstream weak surface convergence is further expanding convective
initiation along the mean cell motion path... a few spots of 3-4"
are becoming increasingly probable. Intersection with larger
urban centers like Alexandria, Natchitoches and perhaps Layfette
and Lake Charles toward 00z, late evening... will garner the
greatest potential for possible rapid inundation flooding.