293
AWUS01 KWNH 290701
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-TXZ000-OKZ000-291300-

Mesoscale Precipitation Discussion 1022
NWS Weather Prediction Center College Park MD
300 AM EDT Fri Aug 29 2025

Areas affected...Northeast TX...Far Southern AR...Northern and
Central LA...Central and Southern MS

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

Valid 290700Z - 291300Z

SUMMARY...Expanding bands of heavy showers and thunderstorms with
cell-training concerns are expected going through mid-morning.
This will gradually pose a concern for areas of flash flooding.

DISCUSSION...The latest GOES-E IR satellite imagery is gradually
showing an uptick in cooling convective tops near the Arklatex
region, and with additional broken bands of elevated convection
extending off to the southeast across northern LA and through
central MS.

A gradual increase in warm air advection/isentropic ascent is
noted on the poleward side of a quasi-stationary front and within
a very moist and moderately unstable airmass. MUCAPE values are as
high as 1000 to 2000 J/kg along the front involving eastern TX
through central LA, however, much of the elevated convection is
rooted within the instability gradient farther north along the
AR/LA border along with adjacent areas to the west and east. This
is also where there is some modest frontogenesis and related
forcing seen in the 925/850 mb layer. Meanwhile, the PWs are on
the order of 2.0 to 2.25 inches and suggestive of a very tropical
environment.

The flow aloft is becoming increasingly divergent as an
upper-level jet streak rounds into the base of the deeper layer
trough over the Mid-South/OH Valley region, and this should drive
a low-level response this morning with an additional increase and
gradual veering of the low-level flow across eastern TX and
central LA. This will interact with the aforementioned frontal
zone and promote stronger isentropic ascent and frontogenetical
forcing.

This along with the pool of instability that is available will
favor additional development and expansion of heavy showers and
thunderstorms with at least some loose organization given
proximity of 30 to 40 kts of effective bulk shear. Propagation
vectors are relatively weak which suggests there may be some
attempt at some backbuilding cells, and given the linear nature of
some of these elevated bands of convection, there will be concerns
for cell-training.

Rainfall rates will be very high and capable of reaching 2.5
inches/hour given the level of moisture and instability, and with
the backbuilding/cell-training concerns, some rainfall totals
going through mid-morning may reach 3 to 5+ inches.

A gradual southward advance of the overall convective footprint is
expected over the next several hours, but with these rains, there
may be areas of flash flooding that materialize and especially for
the more sensitive urban environments.

Orrison

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...FWD...JAN...LCH...LIX...LZK...MOB...OUN...SHV...
TSA...

ATTN...RFC...ALR...FWR...ORN...TUA...NWC...

LAT...LON   33989551 33699411 33259262 32829060 32558959
            32318886 31518832 30338870 30189014 30679292
            31249453 32199614 33229668 33879630