Mesoscale Precipitation Discussion 1006
NWS Weather Prediction Center College Park MD
150 AM EDT Sat Sep 14 2024
Areas affected...Large areas of Northwest to South-Central AL
Concerning...Heavy rainfall...Flash flooding possible
Valid 140550Z - 141045Z
SUMMARY...Slow-moving and locally training bands of heavy showers
and thunderstorms will continue to foster potential areas of flash
flooding overnight.
DISCUSSION...The latest GOES-E IR satellite imagery shows a few
broken linear bands of shower and thunderstorm activity continuing
to impact areas of northwest through south-central AL with the
convection well-aligned with the leading edge of a well-defined,
but very slow-moving frontal occlusion. This is all in association
with Post-Tropical Cyclone Francine which is still impacting the
Mid-South.
The latest RAP analysis shows a well-defined and fairly strong
moisture convergence axis coinciding with modest instability in a
north-northwest to south-southeast fashion across the region.
MUCAPE values are in the order of 500 to 1000 J/kg and PWs across
the region are quite moist with values of 1.7 to 1.9 inches based
on the latest GPS-derived data.
Some cyclonic pivoting of the convective bands are expected going
through dawn as Francine's weakening circulation loses latitude in
response to strong ridging to its north over the OH Valley. This
will favor some of the persistent bands of convection pivoting and
locally training over the same area. However, the convection
should tend to be broken in nature.
Rainfall rates with the stronger convective cores going through
the remainder of the night will still be capable of reaching up to
1 to 2 inches/hour. Given the linearly oriented and locally
training bands of convection and slow cell-motions, some
additional rainfall totals going through the remainder may reach
as high as 2 to 4 inches. This is generally consistent with the
00Z HREF guidance which suggests that areas of north-central to
northwest AL will likely tend to have the heaviest concentrations
of rain over the next several hours.
Additional areas of flash flooding will be possible overnight and
especially with increasingly wet antecedent soil conditions from
rainfall over the last 24 to 36 hours.
Orrison
ATTN...WFO...BMX...HUN...MEG...MOB...OHX...
ATTN...RFC...LMRFC...SERFC...NWC...
LAT...LON 35228734 34558654 32618617 31458630 31208681
31408727 31978757 33118779 34358818 35058812
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