193
AWUS01 KWNH 171705
FFGMPD
PAZ000-MDZ000-VAZ000-WVZ000-OHZ000-172303-

Mesoscale Precipitation Discussion 0468
NWS Weather Prediction Center College Park MD
104 PM EDT Tue Jun 17 2025

Areas affected...Eastern OH Valley...Central Appalachians

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

Valid 171703Z - 172303Z

Summary...Repeating rounds of showers and thunderstorms containing
rainfall rates exceeding 2"/hr at times are expected to produce
scattered to numerous instances of flash flooding this afternoon
-- some significant.

Discussion...Recent trends in Day Cloud Phase RGB and
LightningCast data suggest convection is developing over the Ohio
River Valley and and Central Appalachians as steady moistening and
insolation occur ahead of an approaching vort max in the
Mid-South. A recent cluster of cells near Pittsburgh produced
radar estimated rainfall rates of 1-2"/hr, prompting two Flash
Flood Warnings.

While this activity remains fairly scattered as of now,
mesoanalysis, GPS, and earlier regional soundings show an
increasingly unstable and saturated airmass available for these
maturing cells to tap into, with 1000 J/kg of MLCAPE (with no
CIN), 1.9-2" PWATs (above the daily max for many sites), and
13,000-14,000 foot warm cloud depths. Individual cell motions will
likely be somewhat progressive owing to 25-30 kts of effective
shear across the region, but should assist with overall cell
longevity.

Going forward, the expectation is for coverage and intensity of
cells to increase as the moistening and heating continues while
the upstream vort-max slowly lifts into the Ohio Valley this
afternoon. The overall setup should favor repeating rounds of
thunderstorms along a SSW to NNE axis, with the HREF highlighting
increasing probabilities of 1-2"/hour rainfall rates beginning
around 17-19z. As these rates are realized, both the HREF and REFS
neighborhood probabilities show a high likelihood (above 50%) of
1-3 HR FFG exceedance  through 22-23Z. However, even outside of
the area of most intense rates, the combination of repeat rounds
of thunderstorms and low FFGs (at or below 1") suggests scattered
to numerous instances of flash flooding are likely -- some
significant.

Asherman

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

ATTN...WFO...AKQ...CLE...CTP...LWX...PBZ...RLX...RNK...

ATTN...RFC...ALR...RHA...TIR...NWC...

LAT...LON   41417891 40977746 39777721 38537752 37537917
            37268015 37648091 38698109 39728184 40428174
            41168042