Flash Flooding and Flood in Mississippi, April 10, 2024

Area Forecast Discussion
National Weather Service Memphis TN
620 AM CDT Wed Apr 10 2024

...New AVIATION...

.SYNOPSIS...
Issued at 254 AM CDT Wed Apr 10 2024

Wet and unsettled weather will continue for the next 24-36 hours
as a cold front and deep low pressure system traverse the area.
An additional 2-3 inches of rain is possible today, especially
across north Mississippi. A low confidence severe weather threat
also exists across the area this afternoon. After the front moves
through tomorrow, expect gusty winds on the back side of the
system. Dry weather and mild temperatures return Friday through
this weekend.

&&

.DISCUSSION...
(Today through Tuesday)
Issued at 254 AM CDT Wed Apr 10 2024

A surface low is forecast to materialize over SE TX later this
morning, deepening as it ejects across the ArkLaTex up through
the TN Valley. An associated warm front will also begin lifting
north throughout the day as the surface low occludes. While much
of the ongoing stronger convection will remain confined to
central and south MS in the open warm sector, the latest CAMs
suggest another wave of showers and thunderstorms will surge up
along the warm front later this morning. Expect a broad swath of
heavy rain with the occasional embedded strong thunderstorm to
follow the evolution of the occluded surface low.

Forecast soundings for today depict a classic high shear, low CAPE
environment. The column is extremely saturated across most of the
area, which has further limited instability given the last 24
hours of steady rain. HREF probabilities of CAPE > 500 J/kg colocated
with higher dBZ are quite low overall (average 20%), but are
maximized across the MS Delta into West Tennessee in the 12PM-4PM
time frame today. Storm mode will likely be quite messy and
disorganized across the Mid-South today on the northern flank of
the warm front. The more organized convection and/or linear storm
modes will stay along the cold front as it treks across central
and south MS/AL. Still, a low confidence conditional severe threat
exists for much of the area today, especially south of I-40. All
hazards will be on the table.

The more noteworthy impact of this deep low pressure system will
be the additional rainfall and flooding potential it will bring
this afternoon. Forecast PWATs exceed 1.6 inches south of the
TN/MS state line, which is nearing the maximum of NAEFS
climatology for this time of year. Additional QPF today is
expected to be around 2-3 inches for some parts of north
Mississippi and even eastern AR. On top of the 3-4 inches of rain
that has already fallen over the last 24 hours, this will elicit a
very quick flooding response in urban and low-lying areas. As
such, the Flood Watch remains in effect until 7AM tomorrow.

The deeply occluded surface low's trajectory crosses right over
west Tennessee overnight tonight. It's a very progressive system
aided by an anomalously strong meridional jet. As a result, the
pressure gradient will tighten very quickly over the Mid-South
tonight, subsequently increasing winds. A Wind Advisory was
debated for the overnight period, but the strongest winds look to
be too short-lived to warrant an Advisory and mostly confined to
north Alabama. However, high res models are indicating the
potential for a wake low to develop across west TN on the back
side of the system tomorrow morning. Tomorrow (Thursday) may be
more likely to meet Wind Advisory criteria for long enough to
warrant a headline, but confidence was still too low for issuance
this morning.

Showers should taper off from west to east tomorrow as the front
pulls away. Expect a very pleasant and much needed dry period
Friday through Sunday under the influence of upper level ridging.
Afternoon highs should be slightly above normal in the upper 70s
this weekend, warming further to the lower 80s by Monday as
return flow sets back up over the Lower MS River Valley. PoPs are
generally in the 20-30% range early to mid week as a slow moving
cold front approaches from the central Plains.

CAD

&&

.AVIATION...
(12Z TAFS)
Issued at 616 AM CDT Wed Apr 10 2024

A developing surface low over north Mississippi will result in
strengthening, gusty and variable wind today, but the prevailing
direction should be from the south before an occluded front moves
across the region late tonight. Showers and thunderstorms are
likely today and tonight resulting in brief gusty wind and periods
of IFR visibility. Winds should shift northerly before sunrise.
Borderline LLWS conditions early this morning should diminish
after sunrise.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...Flood Watch through Thursday morning for ARZ049-058.

MO...None.
MS...Flood Watch through Thursday morning for MSZ001>017-020>024.

TN...None.
&&

PUBLIC FORECAST...CAD
AVIATION...JDS