024
AWUS01 KWNH 270450
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-270915-

Mesoscale Precipitation Discussion 0857
NWS Weather Prediction Center College Park MD
1250 AM EDT Mon Jul 27 2026

Areas affected...central IL into Lower OH Valley and western TN

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

Valid 270449Z - 270915Z

SUMMARY...At least localized flash flooding will be likely across
portions of the Midwest from central IL into the lower OH Valley
and western TN through 09Z. Training of thunderstorms will allow
for 1 to 2 inches of rain in an hour with isolated higher hourly
totals possible. Additional storm total rainfall through 09Z of 2
to 4+ inches will be possible.

DISCUSSION...Area radar imagery across southwestern IN into
portions of northern KY at 0430Z showed a compact cluster of
thunderstorms with some recent expansion in coverage. Training of
cells was coincident with MRMS-derived hourly rainfall just over 1
inch in a few locations in and around the western IN/KY border.
These cells were elevated on the cool side of an outflow
reinforced frontal boundary that draped from west-central IL into
western TN. 925-850 mb layer winds were from the WNW along the MS
River, veering to more of a NNW direction along the southern IL/IN
border. Overrunning of the relatively colder airmass and
directional low level convergence was supporting the convection
beneath diffluent flow aloft. The airmass across the Midwest was
strongly unstable with 2000-4000 J/kg MUCAPE and very moist with
PWs of about 2.0 to 2.4 inches via the 04Z SPC mesoanalysis.

While the persistence of convection across the region is a bit
uncertain due to poor hires model handling of the current
activity, the same larger scale forcing mechanisms will generally
remain in place over the next 3-5 hours. This should allow
training potential to linger for at least another few hours with
hourly rainfall of 1 to 2 inches at times (locally higher) due to
training of cells following the mean steering flow from NNW to
SSE. Some upstream convective development will be possible farther
north into central IL later tonight due to the presence of
uninhibited elevated instability and subtle upstream vorticity
maxima within the northwesterly flow aloft. At least isolated
flash flooding appears likely with 3-hr flash flood guidance
values of 2 to 3 inches across a majority of central IL into Lower
OH Valley and western TN.

Otto

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

ATTN...WFO...ILX...IND...LMK...LOT...LSX...MEG...OHX...PAH...

ATTN...RFC...MSR...ORN...TIR...NWC...

LAT...LON   40478839 39478717 37828671 36598690 35988766
            35968855 36558930 37638956 39968955