Mesoscale Precipitation Discussion 0895
NWS Weather Prediction Center College Park MD
546 PM EDT Tue Sep 25 2018

Areas affected...Eastern PA...Central/Northern NJ...NYC metro...CT
River Valley

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

Valid 252145Z - 260130Z

Summary...Ongoing flooding and flash flooding due to steady
moderate to locally heavy rain will continue for a more hours
across the CT River Valley to the NYC metro southwest into the PHL
metro areas.

Discussion...Surface analysis late this afternoon showed a
stationary boundary draped along the coast from RI into NJ. Strong
convergence and isentropic lift over this boundary combined with
enhanced lift from a departing shortwave has kept a large shield
of moderate to locally heavy rain in place from near the PHL metro
through NYC into CT and southern MA since late this morning.
Recent totals range from 3 to locally 5 inches with 1-hr rates of
2-3 in/hr across southern CT.

Recent runs of the HRRR and RAP show pockets of heavy rainfall
likely to continue through early evening, especially across
portions of CT into western RI and southern MA. While forcing and
convergence will wane some, there should be persistent training
and redevelopment over the area to support additional rainfall
totals of 1-3 inches. HREF probabilities show strong signals for
exceeding 1 to 2 inches in the next few hours from near NYC into
CT.

Given the sensitive urban corridors and modestly low FFG values,
the threat of flash flooding will continue for a few more hours.

Further southwest across NJ/PA including the PHL metro, ongoing
flash flood threat should be peaking now and will begin to lessen
in the next 1-2 hours as forcing departs and flow becomes less
convergent.

Taylor

ATTN...WFO...ALY...BOX...OKX...PHI...

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

LAT...LON   42657237 42547152 42207113 41577130 41127194
            41057254 40797327 40267429 39947481 39817534
            40187565 40527546 40917512 41267472 41547391
            41897340 42307285