Mesoscale Precipitation Discussion 0220
NWS Weather Prediction Center College Park MD
702 PM EDT Sun May 04 2025

Areas affected...Northeast PA...Central to Southeast NY...Portions
of Southern New England

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

Valid 042302Z - 050502Z

SUMMARY...Concentrations of heavy and slow-moving showers will
continue into the evening hours across portions of northeast PA,
central to southeast NY and parts of southern New England. A
threat for some flash flooding will continue given localized
persistence of some of the heavier showers.

DISCUSSION...Generally no change to the earlier MPD reasoning
across the region. The large scale pattern across the Eastern U.S.
features a deep layer cyclone over the OH Valley with an occluded
surface low structure and a stationary front that extends east
across central to eastern PA and into southern New England. A
rather deep warm/moist conveyor belt continues to only slowly
shift eastward with time along the East Coast, but continues to
channel an axis of 1.25 to 1.5 inch PWs northward up toward areas
of the northern Mid-Atlantic and southern New England.

Radar imagery shows an area of slow-moving but locally heavy
shower activity impacting areas of northeast PA through parts of
central and southeast NY where recently there has been some
rainfall rates reaching upwards of 1 to 1.5 inches/hour based on
MRMS data. Meanwhile, with aid of the broader warm air advection
regime, an axis of locally heavy rainfall is also noted from
eastern NY over into far northwest MA, southern VT and southern
NH. Much of the rainfall in general across the region is being
aided by a combination of frontogenetical forcing and elevated
instability. The best instability is along the front itself with
areas of central and eastern PA seeing MUCAPE values of 500 to
1000 J/kg.

Some persistence of locally heavy shower activity with some
cell-training concerns will continue into the evening hours across
the region with rainfall rates still capable of reaching 1 to 1.5
inches/hour where stronger convective elements near the front
materialize. Some additional rainfall amounts of 2 to 3 inches
will be possible locally. As a result, some additional localized
runoff problems and flash flooding will be possible.

Orrison

ATTN...WFO...ALY...BGM...BOX...BTV...GYX...OKX...PHI...

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

LAT...LON   43517287 43507113 43117078 42667137 42447252
            41417381 41147528 41367594 42057599 43007480