894
AWUS01 KWNH 232314
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-240510-

Mesoscale Precipitation Discussion 1045
NWS Weather Prediction Center College Park MD
714 PM EDT Mon Sep 23 2024

Areas affected...southeastern MO/northeastern AR into Mid-MS
Valley

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

Valid 232312Z - 240510Z

SUMMARY... The potential for SW to NE training of heavy rain will
increase overnight from the eastern AR/MO border region into the
and across the MS River. Rainfall rates of 1-2 in/hr are expected
with totals of 2 to 4 possible on a localized basis.

DISCUSSION...Fading visible satellite imagery at 23Z and regional
radar imagery showed a recent increase in the intensity of
thunderstorms over northern AR into MO, especially with a small
line segment located between STL and UNO. Additionally, a
northeastward tracking mesolow was observed in northern AR,
co-located with a small area of showers to its north. The regional
uptick in convection was occurring ahead of an upper level
vorticity max over western MO seen on water vapor imagery,
tracking ENE. At the surface, a low was located about 75 miles
southwest of STL with a stationary front extending eastward into
southern KY and cold front extending southward from the low into
west-central AR. Earlier clearing on visible imagery ahead of the
cold front from northeastern AR into southeastern MO had allowed
for greater coverage of 500-1500 J/kg MLCAPE located in the warm
sector over southeastern MO via SPC mesoanalysis data. Moisture
via area GPS observations and mesoanalysis data revealed values of
1.5 to 1.8 inches throughout the Mid-MS Valley.

As the upstream vorticity max/trough axis continue to move east
overnight, thunderstorm coverage is expected to expand across
southeastern MO/northeastern AR into southern IL, especially for
locations near/north of the stationary front. Some modest increase
in 850 mb flow is expected beyond 00Z ahead of the trough with
greater coverage of 20-25 kt southwesterlies forecast through 04Z
by the latest RAP which should lead to greater isentropic ascent
from the MO/IL border into southern IL and western portions of KY.
Due to unidirectional southwesterly flow ahead of the cold front,
instances of southwest to northeast training will be favored as
the general precipitation axis advances toward the east, ahead of
the upstream upper vort/trough axis. Rainfall rates of 1-2 in/hr
and localized maxima of 2 to 4 inches will be possible

Otto

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

ATTN...WFO...ILX...LSX...LZK...MEG...PAH...SGF...

ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON   39338855 38468784 36748875 36378912 35798979
            35479042 35419117 35679184 36149221 37119221
            38239099 38998989