AWUS01 KWNH 120901
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-121500-

Mesoscale Precipitation Discussion 0993
NWS Weather Prediction Center College Park MD
500 AM EDT Thu Sep 12 2024

Areas affected...Much of MS...Western AL

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

Valid 120900Z - 121500Z

SUMMARY...Moderate to heavy rain associated with weakening
Tropical Storm Francine will continue to foster a threat for areas
of flash flooding going through the morning hours.

DISCUSSION...Tropical Storm Francine at 09Z (4AM CDT) is located
60 miles north of New Orleans, LA and is moving northeast at 12
mph. The storm continues to rapidly weaken as it moves farther
inland, and the latest radar and satellite data suggests Francine
is rather quickly acquiring extratropical characteristics as the
storm merges with a frontal zone and an approaching upper-level
trough to its west over the lower MS Valley.

Francine currently has a distinct lack of convection near the
center, with much of the heavy rainfall now north of the center
over central MS, and also in several convective bands well east of
the center involving southwest AL and the western FL Panhandle.
The rainfall over much of central MS is being driven by strong
warm air advection/isentropic ascent given interaction with the
aforementioned frontal zone. A southerly low-level jet of 40 to 60
kts is seen advancing north around the eastern quadrant of
Francine's circulation, and this is a key player in driving
enhanced low-level forcing and moisture transport.

Much of the stronger instability is becoming detached from
Francine's center of circulation, and this has been allowing for
the rainfall rates to come down rather substantially over the last
few hours. However, going through the morning hours, the level of frontogenetical forcing, moisture transport and interaction with
the aforementioned upper-level trough should still yield areas of
heavy rainfall with rates that may still occasionally reach 1 to
1.5 inches/hour.

The 00Z HREF guidance suggests additional rainfall amounts going
through 15Z (10AM CDT) of 2 to 4 inches, with isolated heavier
amounts. The antecedent conditions across especially areas of
central and northern MS and western AL are quite dry, so these
rains will initially be going into moistening the soil conditions.
However, given the localized persistence of heavier rainfall rates
and urban sensitivities, some runoff problems and areas of flash
flooding will be possible this morning.

Orrison

ATTN...WFO...BMX...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34139023 34138949 33908861 33318800 32698774
31998780 31548820 31308908 31459011 32119101
33119123 33839095
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AWUS01 KWNH 090920
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-091500-

Mesoscale Precipitation Discussion 0409
NWS Weather Prediction Center College Park MD
519 AM EDT Mon Jun 09 2025

Areas affected...Central MS...Southwest AL...

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

Valid 090920Z - 091500Z

SUMMARY...Training WAA convective cells with capability of 2"/hr
rates and spots of 2-3"+ may result in possible localized
incident(s) of flash flooding through early morning.

DISCUSSION...Regional RADAR and surface observations show rapidly
decaying MCS continuing to press eastward along the LA/AR border
with outflow boundary starting to reach northeast LA where it
intersects with slowly lifting frontal boundary that has had some
active convection along it earlier this mornign across S MS.
Surface to boundary layer winds are increasing with approach of
the MCS and slightly increased WAA over the boundary breaking out
more numerous updrafts across central MS connecting up to the
lifting older cluster out of south-central MS. From 850-500mb,
winds are fairly flat from west to east to allow for solid
potential for training of these cells. CIRA LPW also denotes the
weak amplifcation of the surface to 850mb moisture up the MS River
Valley but also still pooled along the deeper layer boundary
toward SW AL and active cluster in south-central AL as well. TDs
in the mid-70s with 850-500mb moisture axis continue to support
2-2.25" total PWats and with upstream faster flow associated with
the MCS, propagation vectors have reduced to about 5kts and are
supportive of backbuilding into the approaching outflow boundary.
As such a few hours of efficient rainfall/training should allow
for 2-3"+ totals across central MS.

Slowly the cells will move into more senstive soil conditions from
east-central MS into south-west AL from last evening's heavy
rainfall, this may increase the potential for higher than normal
run-off and incidents of flash flooding, but the air is drier
aloft and more stable, and without very strong WAA to advect
northward it may be more difficult to maintain stronger convection
across this region, but at the same time, will not require as much
rainfall totals (2-2.5" in 3-6hrs) than over the drier conditions
of central MS. Either way, hourly rates and 3hour totals will be
close enough to suggest localized incidents of flash flooding will
be possible through early morning hours.

Gallina

ATTN...WFO...BMX...JAN...MOB...

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

LAT...LON 33649014 33468862 32828762 32548709 32258628
31638628 31168664 31268799 31788932 32029021
32289124 32859149 33449128

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