AWUS01 KWNH 221450
FFGMPD
DEZ000-MDZ000-VAZ000-222030-

Mesoscale Precipitation Discussion 1111
NWS Weather Prediction Center College Park MD
1049 AM EDT Sat Aug 22 2026

Areas affected...Middle to Lower Chesapeake Bay Region...

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

Valid 221450Z - 222030Z

SUMMARY...Slow moving/training warm-cloud efficient rainfall
production to 2.5"/hr pose localized flash flooding with 2-4"
totals in 1-3hrs.

DISCUSSION...GOES-E WV and Regional RADAR shows a shortwave
feature moving northeast in the warm conveyor belt southeast of
the tip of the Delmarva Peninsula; while the expanding right
entrance region of a 80-90kt 300mb jet remains directly overhead. 
This direct circulation is tightening (FGEN) a SW to NE
convergence/deformation zone across South-central MD into southern
DE.  An axis of modest but sufficient low level unstable air
existed through the lower Chesapeake Bay with a wedge of 1000 J/kg
of MUCAPE residing along this axis of deep layer moisture
convergence.  As such, shallow thunderstorms developed across
Charles to N Calvert county and extend through the Bay toward
Talbot county.  The shallow nature though with solid moisture flux
through channeling up the Bay supports efficient
tropical/warm-cloud rainfall production to support 2-2.5"/hr
rates.   In addition, localized frictional convergence along the
edges/inlets of the Bay has resulted in more scattered/isolated
but equally efficient heavy rainfall producing cells.   Deep layer
steering and fairly stationary right entrance region suggest slow
forward propagation through the Bay toward the Eastern Shore over
the next few hours.

Observations so far of 1.5 to 3" in about 60-90 minutes and while
the area is fairly sandy in soil type, MRMS Flash response is
reaching 200-300 cfs/sqmi suggestive of localized flash flooding
may be starting soon.   Hi-Res CAMs all generally show a core of
2-4" additional totals through 21z, mainly focused directly over
the Bay and nearby coastal areas, though some solutions hint of
higher localized totals of 5"+ as well, suggesting flash flooding
will remain possible into the afternoon hours across the Delmarva
Peninsula, Southern Maryland and the northern Neck of VA. 

Gallina

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

ATTN...WFO...AKQ...LWX...PHI...

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

LAT...LON   38917573 38667525 38287505 37747541 37497564 
            37467600 37797669 38177699 38567702 38907660