AWUS01 KWNH 261945

FFGMPD

NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-270145-



Mesoscale Precipitation Discussion 0520

NWS Weather Prediction Center College Park MD

344 PM EDT Thu Jun 26 2025



Areas affected...Mid-Atlantic



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



Valid 261945Z - 270145Z



SUMMARY...Increasing number of thunderstorms will producing

downpours containing hourly rainfall rates >2"/hr in some cases.

Flash flooding is possible in impacted areas, especially areas

with saturated soils and within more urbanized communities.



DISCUSSION...The Mid-Atlantic is caught between a series of

converging surface boundaries. A back-door cold front is

approaching from the east, marching through the Delaware Valley

and slowly making its way towards the northern neck of the

Chesapeake Bay. To the north and west, a stationary front and the

added help of a lake breeze off Lake Erie has triggered

thunderstorms over northeast Ohio that are tracking southeast into

western PA. Plus, strong surface based heating has been unfolding

across the region that is causing a burgeoning field of

cumulonimbus clouds along the Central Appalachians. The 12Z IAD

RAOB showed a convective temp of 93F, which most areas from

southeast PA on south through MD and into northern VA have all

reached as of 19Z. Storms are initiating within an environment

that is likely to have anywhere from 1,000-2,000 J/kg of MLCAPE

and PWs that range between 1.75" from western and central PA to

>2.0" from the DC/Baltimore area on east to the northern DelMarVa

Peninsula. Vertical wind shear soundings show generally weak shear

aloft, making storm modes largely pulse-like in nature. However,

outflow boundaries emanating from these first batch of storms will

fire additional thunderstorms that congeal into larger clusters in

parts of the Mid-Atlantic this evening.



The 12Z HREF's probabilistic guidance is keying in on the greater

DC/Baltimore metro area on north into the Lower Susquehanna Valley

with the low-to-moderate chances (30-60%, highest probs in the DC

metro area on east to the MD Eastern Shore) for >3" of rainfall

between 21-03Z this evening. Farther west, thunderstorms

propagating southeast from western OH will be a focus for

additional thunderstorm development, as will areas along and north

of I-80 where differential heating is becoming more pronounced.

Some thunderstorms will be capable of producing >2"/hr rainfall

rates given the available instability and moisture parameters,

making places with sensitive soils (>80% 0-40cm soil saturation in

northern WV, western and central PA) and heavier urbanized

environments particularly susceptible to flash flooding this

evening. Thunderstorm coverage should begin to fade after 03Z

given the marginal vertical wind shear aloft and loss of daytime

heating.



Mullinax



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



ATTN...WFO...AKQ...BGM...CTP...LWX...PBZ...PHI...RLX...



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



LAT...LON   41827623 41367525 40217554 39507507 38347547 

            37847628 37867748 37917902 38597966 40078014 

            40907993 41327907 41587753 

