Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Jun 11 2023 06:01:50

AWUS01 KWNH 110601
FFGMPD
ILZ000-MOZ000-111200-

Mesoscale Precipitation Discussion 0461
NWS Weather Prediction Center College Park MD
201 AM EDT Sun Jun 11 2023

Areas affected...North-Central MO...Southwestern IL

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

Valid 110600Z - 111200Z

Summary...Localized rainfall rates of 1-2"/hr may result in
isolated totals of 2-3"+ (and possible flash flooding) through
dawn.

Discussion...A slow moving mid-upper level low located over the
Middle MS Valley may help to focus and intensify (so-far) fairly
disorganized convection through dawn across MO/IL. The axis of
greatest concern is from northwest MO eastward into southwest IL,
where the associated surface cyclone and frontal features are
oriented with the best potential for banding/repeating of rainfall
rates locally as high as 1-2"/hr. The mesoscale environment is
currently characterized by relatively weak instability (SB CAPE
generally 250-750 J/kg), rather high PWATs of 1.4-1.8 inches (near
the 90th percentile, per SGF and ILX sounding climatology), and
effective bulk shear of less than 20 kts. Of these parameters, the
PWATs are most impressive with large-scale lift (provided by DPVA
in association with the mid-upper low/shortwave) and focused deep
layer moisture flux convergence along the front possibly making up
for lack of shear (with instability being sufficient enough for
heavy rainfall, given the localized 1-2"/hr rates being realized
already). It would only take a couple hours of these locally high
rates to approach FFGs of ~2.5 inches.

The 00z HREF guidance provided a good starting point for
identifying the area of concern, with 40-km neighborhood
exceedance probabilities indicating a swath of 30-50% odds for 2"
exceedance, and 10-20% odds for 3" exceedance (over a 6-hr period
through 12z). Hourly runs of the HRRR since 23z depict a very
similar QPF amounts, with splotchy isolated totals in that 2-3"+
range (probably amounting to less than 10% of the total area of
the MPD). Given the localized nature of the heavy rainfall and
overall dry antecedent conditions across the region (with much of
north-central MO in particular experiencing drought), isolated
instances of flash flooding are considered possible.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8MgePvmDuXtHQESd8LGylVay1FcilYliH8wbR5SPatQrpfASucZ16rUloTnumQ9VDZpt=
ydMtLZ1f6H7SvsxfVZRR5-4$  for graphic product...

ATTN...WFO...EAX...ILX...LSX...PAH...SGF...

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

LAT...LON   39979282 39969095 39688984 39348899 38868870=20
            38428880 38008915 37788968 37849041 38239157=20
            38549275 38529439 39609434=20

=3D =3D =3D
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