AWUS01 KWNH 201139
FFGMPD
PAZ000-MDZ000-WVZ000-OHZ000-201700-

Mesoscale Precipitation Discussion 1097
NWS Weather Prediction Center College Park MD
738 AM EDT Thu Aug 20 2026

Areas affected...Eastern Ohio...Northern West Virginia...Western Maryland...Southwest to Central Pennsylvania...

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

Valid 201140Z - 201700Z

SUMMARY...Solid speed, directional and upslope moist flow along a
training warm advection wing of MCV proving to be efficient rain
producer at 1-1.5"/hr. Low FFG and relatively saturated upper
soils through rough terrain support possible incidents of flash
flooding this morning.

DISCUSSION...Regional RADAR and surface observations continues to
show a core of enhanced efficient rainfall just downstream of a
tight compact deep layer cyclone near ZZV moving east. VWP and
RAP analysis shows broad 15-20kt SSW flow through the Ohio Valley
quickly turning south along a well defined west to east
convergence axis downstream of the cyclone to south-central PA.
This is aligned with enhanced .66-.75" surface to 850mb LPW per
CIRA. Though moisture and flux convergence is solid, much of the
mid-level instability has been limited to about 250-500 J/kg.
However, with a fairly high elevated freezing level/WBZ level, any
shallow convection has been efficient in low warm cloud processes
allowing for 1-1.5" hourly rates near the core.

Also with upslope flow and cyclonic curvature and downstream
convergence along the effective warm front has been producing
scattered warm advective showers pre-cursory to the wave. As
such, these showers may allow for additional .5" prior to arrival
of heavier rains. Spots of 1.5-2" are probable through the
morning. The concern is the area has seen prolific rainfall over
the last few weeks and soil conditions are about 55-70% saturated
per NASA SPoRT 0-40cm LIS product which is about the 80-90th
percentile. FFG values about 1"/hr and 1.5-2"/3hrs have good
possibility to be exceeded along the potential repeating
convergence axis suggesting incidents of flash flooding are
possible through the remainder of the morning into early afternoon.

Gallina

ATTN...WFO...CTP...LWX...PBZ...RLX...

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

LAT...LON 41207837 40787761 40097778 39777837 39527920
39208064 39438182 40208194 41067989

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