Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Jul 30 2024 00:42:30

AWUS01 KWNH 300042
FFGMPD
OHZ000-KYZ000-INZ000-ILZ000-MOZ000-300700-

Mesoscale Precipitation Discussion 0756
NWS Weather Prediction Center College Park MD
839 PM EDT Mon Jul 29 2024

Areas affected...southern IN

Concerning...Heavy rainfall...Flash flooding likely

Valid 300100Z - 300700Z

Summary...A favorable environment for organized convection should
yield thunderstorms capable of 1-3"/hr rainfall rates. Localized
totals of 3-5" are expected. Scattered instances of flash flooding
are likely (with some locally significant over potions of southern
IN and surroundings).

Discussion...Convection is beginning to manifest over portions of
the Midwest/Ohio Valley, in the vicinity of a warm front with an
attendant weak surface low pressure located near Chicago. An
upper-level trough (at 500 mb) trails just upstream (near a
corresponding surface cold front), which should provide the
trigger for deeper convective initiation. Ample instability
(2000-4000 J/kg) and effective bulk shear (30-40 kts) should act
to quickly organize convection, which should eventually allow for
upwind propagation towards the south (likely as an MCS). In the
meantime, single cell and multi-cell clusters will favor a more
west-to-east motion (following the deep layer mean wind), which
could favor localized training/repeating initially. With PWATs of
1.7-2.0 inches (between the 90th percentile and max moving
average, per ILN sounding climatology), storms will be capable of
very heavy rainfall (1-3"/hr rainfall rates).

Hi-res model guidance has consistently depicted an organized heavy
rainfall signal since the 12z HREF suite, though the 18z NAM-nest
and more recent HRRR runs have backed off on the magnitude of the
signal some (as indicated by a downward trend in the 40-km
neighborhood exceedance probabilities of the 18z HREF). Even
still, the probabilities for 5" exceedance are impressive, peaking
between 15-25% over southern IN and adjacent portions of KY. This
corresponds with high odds of 10-yr ARI exceedance (30-60%) and
appreciable odds for 100-yr ARI exceedance (10-20%). While the
HRRR has consistently depicted a less intense solution (with
localized totals of only 2-3", and overall less organized), other
HREF members depict a more realistic depiction of organized
convection, suggesting localized totals of 3-5". Given the
impressive environment, scattered instances of flash flooding are
considered likely (and may be locally significant over southern IN
and surroundings, especially if 5"+ totals occur).

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!6M02UoCeX8DLb5hn8eVcDBR-iXT9gpalAubtoX7H6YjYvHTGOgQSofUH-Ch7hxqnHjHD=
BnvdsBUKllIBcZ4Wof-5p8U$  for graphic product...

ATTN...WFO...ILN...ILX...IND...IWX...JKL...LMK...LOT...LSX...
PAH...

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

LAT...LON   40838753 40548572 39738402 38738381 37688423=20
            37138526 37348715 38068938 39709113 40079111=20
            40068996 40338884=20

=3D =3D =3D
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