567
AWUS01 KWNH 301745
FFGMPD
MAZ000-RIZ000-CTZ000-NYZ000-NJZ000-PAZ000-302344-

Mesoscale Precipitation Discussion 0521
NWS Weather Prediction Center College Park MD
145 PM EDT Sun Jun 30 2024

Areas affected...southern New England, southern New York State,
eastern Pennsylvania, northern New Jersey

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

Valid 301744Z - 302344Z

Summary...Bands of scattered thunderstorm activity were moving
quickly to the east, but also merging/training locally to produce
spots of 1+ inch/hr rain rates at times.  These rates could cause
flash flood potential to increase through the early evening.

Discussion...Storms have deepened and expanded in coverage within
a strongly unstable airmass across the discussion area over the
past hour.  The storms are aligned along and just ahead of a
surface cold front across central PA/southern New York and were
embedded in deep westerly flow, promoting 30-40 kt storm motions.
Of particular concern, however, is the alignment of convection
across Connecticut and southern New York favoring training, which
has boosted rain rates into the 1-1.5 inch/hr range, threatening
local FFG thresholds.

Models/observations are in general agreement that storms will
continue to train/expand eastward while propagating
southward/eastward toward more populated locales (including New
York/northern New Jersey, Providence RI, and Boston).  Not only
are FFGs locally lower in some of these areas, but
urban/hydrophobic surface may promote a local flash flood risk
especially where rain rates exceed 1 inch/hr.  Flash flooding is
possible given the aforementioned scenario.

Cook

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

ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...

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

LAT...LON   42537089 41527023 40757201 40067396 40017598
            40717693 41537625 41837532 42327351 42467238