707
AWUS01 KWNH 010329
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-WVZ000-010727-

Mesoscale Precipitation Discussion 0564
NWS Weather Prediction Center College Park MD
1128 PM EDT Mon Jun 30 2025

Areas affected...southern/southeastern Pennsylvania and vicinity

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

Valid 010327Z - 010727Z

Summary...Additional flash flood impacts are possible as deep,
moist convection migrates from west-southwest to east-northeast
across the region.  Over time, nocturnal low-level stabilization
should result in lesser coverage of storms through 07Z.

Discussion...Flash flood potential continues across the discussion
area, with significant impacts noted in/near Lancaster County, PA
recently.  The region remains under the influence of weak
mid-level shortwave troughs passing over the region.  These
troughs were interacting with a very moist, unstable airmass (2+
inch PW values and 1000+ J/kg MLCAPE) to promote scattered to
widespread thunderstorm development.  Some of these storms were
training, with 1-2 inch/hr rain rates falling near Lancaster,
Reading, and surrounding locales on top of saturated grounds that
have already experienced 2-6 inches of rainfall today.  Locally
significant flash flood impacts are expected to continue in the
short term (through 05-06Z).

Over time, nocturnal boundary layer stabilization should result in
a decrease in convective coverage across the discussion area.
However, low-level flow into the discussion area remains strong
(25-30 kts at 850mb) and a pool of 2000+ J/kg MLCAPE resides over
Maryland just south of ongoing, strong convection.  Mid/upper
level fields also aren`t necessarily prohibitive of any
redevelopment of convection through the night.  Although
convective coverage is expected to decrease some over the next 2-4
hours, sensitive areas of southeastern Pennsylvania (especially
those that are already experiencing significant flash flood
impacts) will need to be monitored carefully for additional heavy
rainfall episodes through 07Z/3a EDT.

Cook

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

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

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

LAT...LON   41417691 41187566 40497462 39847443 39317530
            39267695 39767837 40417905 41237832