AWUS01 KWNH 181721
FFGMPD
OHZ000-KYZ000-INZ000-ILZ000-182320-

Mesoscale Precipitation Discussion 0184
NWS Weather Prediction Center College Park MD
120 PM EDT Mon May 18 2026

Areas affected...portions of Indiana, far southeast Illinois, and
far southwest Ohio

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

Valid 181720Z - 182320Z

Summary...Flash flood potential is increasing especially across
central and southern Indiana.

Discussion...A mature convective complex was making steady
eastward progress into western and central Indiana over the past
hour per radar mosaic imagery.  The southern flank of this MCS was
oriented more of a WSW-ENE fashion over southern Illinois, leading
to areas of training.  Furthermore, a shortwave trough evident in
satellite/objective analyses over northern Arkansas was helping to
initiate convection along and south of the leading edge of the
MCS, with several areas of mergers and 2-2.5 inch/hr rain rates
(per MRMS) estimated southwest of Terra Haute (just south of
Effingham).

The overall scenario for flash flooding will translate eastward
through the afternoon, with occasional spots of 1-2.5 inch/hr rain
rates where training/merging is most pronounced.  The rates will
fall on areas of wet soils from prior rainfall, with FFG
thresholds of 1.5 inch/hr at risk of being exceeded on at least an
isolated basis.  Low-level flow drops off considerably with
eastward extent into Ohio, which lends some doubt/uncertainty on
eastward persistence of convection.  Should the convective complex
remain organized, slightly lower FFGs over Ohio would suggest a
continued, yet isolated flash flood threat there.

Cook

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

ATTN...WFO...ILN...ILX...IND...IWX...LMK...PAH...

ATTN...RFC...TIR...NWC...

LAT...LON   40438600 40438459 40228421 39648397 39128462 
            38388651 38438819 39668793 40078728