Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Jul 04 2023 23:01:39

AWUS01 KWNH 042301
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-050049-

Mesoscale Precipitation Discussion 0637...Corrected
NWS Weather Prediction Center College Park MD
700 PM EDT Tue Jul 04 2023

Corrected for "Likely" tag and inclusion of Maryland in geographic
header

Areas affected...Philadelphia Metro and nearby areas of
Pennsylvania, New Jersey, Delaware, and Maryland

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

Valid 042249Z - 050049Z

Summary...A localized, slow-moving cluster of storms near
Philadelphia was producing 1.5-3 inch/hr rain rates, prompting
local impacts from flash flooding.  The flash flood risk should
continue through sunset.

Discussion...A persistent thunderstorm cluster has slowed to
nearly stationary over southwestern New Jersey while backbuilding
across the Philadelphia Metro area.  These cells are forming along
and just northeast of the leading edge of a mature cold pool from
prior convection, which continues to propagate southwestward and
force ascent within a pre-convective airmass characterized by 2000
J/kg MLCAPE and 1.8 inch PW values.  Light, low-level
west-southwesterly flow was also helping to maintain convergence
at the leading edge of the cold pool, while weak/negligible
inhibition and convergence was fostering additional
shower/thunderstorm activity to develop and deepen in the general
vicinity.  Slow movement of these cells and local cell mergers
were resulting in areas of 1.5-3 inch/hr rain rates, resulting in
moderate to high MRMS Flash responses and at least one instance of
water rescues due to intense runoff.

Slow storm motions (partially in tandem with slow southwestward
movement of the cold pool) will allow for localized heavy rainfall
rates to continue along the Philadelphia/Wilmington DE corridor
and surrounding areas for the next couple hours.  Models/CAMs
suggest that the complex will remain strongly tied to the diurnal
cycle, with some lessening of intensity/rain rates expected
toward/after 00Z or so.  Until then, spots of 1.5+ inch/hr rain
rates will continue to cause localized flash flooding especially
in/near urbanized areas.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!72ays621siBHFW3Eg5PQgRUu6qBaq5Ro0vyev_Scxh3vJbWo2UXqGWqbZTj738FGTeDw=
m3wvJ5x-I8V3NvxNFvNrVL8$  for graphic product...

ATTN...WFO...CTP...LWX...PHI...

ATTN...RFC...MARFC...NWC...

LAT...LON   40117552 40067503 39867474 39537474 39317539=20
            39427618 39807621 40077577=20

=3D =3D =3D
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