256
AWUS01 KWNH 132221
FFGMPD
ILZ000-MOZ000-IAZ000-KSZ000-140420-

Mesoscale Precipitation Discussion 0433
NWS Weather Prediction Center College Park MD
620 PM EDT Thu Jun 13 2024

Areas affected...Northern MO...Southeast IA...Central IL

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

Valid 132220Z - 140420Z

SUMMARY...Expanding clusters of heavy showers and thunderstorms
with some periodic cell-training this evening may result in some
scattered instances of flash flooding.

DISCUSSION...The late-day GOES-E Day Cloud Phase RGB satellite
imagery shows multiple expanding supercell convective clusters
across portions of northeast MO and southeast IA which should
continue to grow upscale and extend gradually across central IL
going into the evening hours. The activity is developing just
south of a cold front and in close proximity to a wave of low
pressure advancing east along it. The environment is very unstable
and rather strongly sheared with MLCAPE values of 2500 to 3500
J/kg and 0-6 km effective bulk shear values of 30 to 50 kts.

Stronger low-level convergence and the focused pooling of
instability near and just ahead of the surface low center is
expected to drive a west to east corridor of well-organized
convection over the next several hours which will likely tend to
be maximized by mid to late-evening over areas of central IL.

The 18Z HREF guidance and recent HRRR runs suggest that areas of
northeast MO through especially central IL will tend to have the
heaviest rainfall potential from supercell thunderstorm clusters,
with some periodic instances of cell-training. The PWs in the
pre-convective environment are generally on the order of 1.3 to
1.5 inches, and these values should increase this evening with the
aid of a gradually veering southwest to westerly low-level jet of
30 to 40 kts and overall expansion of deep convection.

Rainfall rates of 1 to 2 inches/hour are likely with the stronger
and more organized cells, and with some considerations of
occasional cell-training, some localized storm totals of 3 to 4
inches will be possible. The 18Z HREF guidance indicates rather
elevated probabilities (40 to 70 percent) of seeing the 3-hour FFG
values exceeded over central IL in the 00Z to 03Z time frame with
lesser probabilities noted farther west over southeast IA and
northern MO.

Scattered instances of flash flooding will be possible going
through the evening hours as a result as these areas of heavy
showers and thunderstorms continue to organize and expand in
coverage.

Orrison

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

ATTN...WFO...DMX...DVN...EAX...ILX...LOT...LSX...

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

LAT...LON   41448874 41208765 40388762 39898840 39479017
            39129302 39209466 39779514 40229456 40709299
            41169100