Mesoscale Precipitation Discussion 0648
NWS Weather Prediction Center College Park MD
725 AM EDT Mon Aug 13 2018

Areas affected...ERN PA...WRN NJ...NRN DE...SRN NY

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

Valid 131124Z - 131554Z

Summary...

Locally heavy rainfall to continue over eastern Pennsylvania and
parts of western New Jersey this morning. Several inches of rain
are possible.

Discussion...

1100Z RADAR and surface observations show a continuation of
moderate to locally heavy rainfall from northern Delaware
north-northwestward through eastern Pennsylvania. Additional
rainfall was located over southern New Jersey. With an upper low
centered near the WV panhandle, an easterly fetch of moisture off
the Atlantic will continue to supply the area with plenty of
moisture (precipitable water values near of just over 2 inches and
increasing over the past few hours per RAP analyses) in a
diffluent environment. 09Z surface analysis shows low pressure
just east of Atlantic City, NJ and a trough on the south side of
the heavy rainfall area with dew points in the low to mid 70s.
Forecast for the next few hours indicate a slow movement northward
of ongoing rainfall/convection through the upper Susquehanna River
basin to the NY border. HRRR runs have had a good handle on most
of the observed precip trends the past few hours and its QPF of
several inches seems realistic based on RADAR estimates of 3-5"
already over southern PA. With already low FFGs (which will be
lower in the short term) flash flooding threat continue through at
least the late morning.

Fracasso/Burke

ATTN...WFO...BGM...CTP...OKX...PHI...

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

LAT...LON   42147718 42107616 41157542 41027531 40727430
            40357399 39827403 38967489 39617560 39887655
            40307754 41137782