Mesoscale Precipitation Discussion 1202
NWS Weather Prediction Center College Park MD
1101 PM EDT Sat Oct 18 2025

Areas affected...northern LA/MS border into north-central MS and
western AL

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

Valid 190259Z - 190800Z

Summary...Training of heavy rain is expected to result in 1 to 2
inches of rain in an hour and localized totals of 2 to 4 inches
through 08Z from the LA/MS border into western AL. These higher
rain rates may result in isolated flash flooding.

Discussion...Radar mosaic imagery from 0230Z showed a NE to SW
axis of thunderstorms extending from western TN into northern and
western MS and far northeastern LA, co-located with an elongated
outflow boundary. A few linear clusters of thunderstorms were also
observed upstream, across southern AR into northwestern LA,
located ahead of the base of an upper trough tracking east through
OK and northern TX. The environment across the Lower Mississippi
Valley was characterized by MLCAPE of 500-1000 J/kg and PWATs
between 1.7 and 2.1 inches per 02Z SPC mesoanalysis data and the
00Z sounding from JAN. Southerly to southwesterly 850 mb winds of
30-40 kt were present from LA into MS, allowing low level moisture
transport and lift atop rain-cooled air with mean storm motions
oriented from the southwest in MS but veering toward the west
across northwestern LA. Flow aloft was diffluent, out ahead of the
base of the larger scale upper trough located over the central U.S.

Given the available instability and source region emanating from
the south, continued forcing via synoptic scale and mesoscale
processes, some filling in of convection between the leading
outflow in MS and trailing activity in northern LA is expected
over the next couple of hours. The potential for training is high
from the MS River eastward, but the duration of training is
questionable. However, even a 30-60 minute window of SW to NE
training should be able to produce 1 to 2 inches of rain with
potential for 2-4 inches if training is able to set up for a bit
longer duration. These rainfall values may result in flash
flooding.

Dry antecedent conditions should limit flash flood potential, but
these locally higher rain rates could focus an isolated threat
across urban locations or other locations of poor drainage. The
flash flood threat is expected to move east out of the area after
08Z.

Otto

ATTN...WFO...BMX...JAN...MEG...SHV...

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

LAT...LON   34128834 33358769 32428824 31579042 31779220
            32609218 33249096 34018968