Mesoscale Precipitation Discussion 0627
NWS Weather Prediction Center College Park MD
1120 AM EDT Wed Jul 09 2025

Areas affected...Upper OH Valley...Central Appalachians/Blue Ridge

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

Valid 091520Z - 092120Z

SUMMARY...Developing showers and thunderstorms will be expanding
in coverage going through the afternoon hours. High rainfall rates
are expected to drive a likelihood for at least scattered areas of
flash flooding.

DISCUSSION...The late-morning GOES-E satellite imagery shows an
elongated shortwave trough gradually transiting the OH Valley
which will be interacting with a moist and increasingly unstable
airmass pooled across the region, and this will set the stage for
developing and expanding clusters of heavy showers and
thunderstorms going through the early to mid-afternoon hours.
Already the latest radar imagery shows a few small-scale clusters
of showers and thunderstorms developing over eastern KY, southeast
OH and central WV.

MLCAPE values have already increased to 1000 to 1500 J/kg with the
aid of morning solar insolation, and PWs of 1.5 to 1.75+ are in
place which are about 1.5 to 2 standard deviations above normal.
Some gradually increasing mid-level west-southwesterly flow will
promote some uptick in shear parameters over the next several
hours with effective bulk shear rising to about 25 to 35+ kts.

These environmental trends should be conducive for seeing bands of
multi-cell convection which will tend to be expanding in coverage
with the aid of differential heating boundaries and orographics,
with cell-motions gradually off to the east that will include far
eastern KY, southeast OH, and much of WV initially. By
mid-afternoon, this activity should then advance or develop across
adjacent areas of the MD/WV Panhandles, western VA and also
northwest NC involving the Blue Ridge and portions of the
Mid-Atlantic Piedmont.

The anomalous PW environment alone will favor high rainfall rates
that may reach as high as 1 to 2 inches/hour which is strongly
favored by the 12Z HREF guidance, but there will potentially be
some orographic/terrain-induced forcing that may elevate these
rates a bit further. This will especially be the case by
mid-afternoon for areas over the central Appalachians and adjacent
areas of the Blue Ridge involving MD/WV/VA.

The 12Z HREF and 06Z REFS guidance collectively suggest some
rainfall total potential by late-afternoon of 2 to 4+ inches.
These rainfall amounts are likely to result in at least scattered
areas of flash flooding.

Orrison

ATTN...WFO...AKQ...CTP...GSP...ILN...JKL...LWX...MRX...PBZ...
RAH...RLX...RNK...

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

LAT...LON   39927742 39767683 38867716 37537862 36607948
            35728092 35488223 35658290 36288278 36728273
            37718283 38878310 39578238 39778093 39757863