647
AWUS01 KWNH 302212
FFGMPD
NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-010330-

Mesoscale Precipitation Discussion 0560
NWS Weather Prediction Center College Park MD
612 PM EDT Mon Jun 30 2025

Areas affected...Eastern OH...West Virginia...Northern
MD...Pennsylvania...Southern NY...Parts of NJ

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

Valid 302210Z - 010330Z

SUMMARY...Unstable, very moist rich environment will likely
continue to support hourly rates of 2"+. Storm interactions with
possible repeating may generate spots of 2-3" resulting in widely
scattered incidents of possible flash flooding past nightfall.

DISCUSSION...GOES-E WV suite depicts a broad area of disturbed
weather at the apex of large scale ridging over the southern
Mid-Atlantic and points south.  A digging large scale trough over
the Upper Great Lakes is providing oblique right entrance ascent
across the Lower Great Lakes, helping to drive deeper layer
southwesterly flow and associated anomalous (1.5-2.5 standard
anomalies) deep moisture through the Upper Ohio River Valley into
the northern Mid-Atlantic and Northeast, ranging mainly above 2",
with spots of 2.25" noted.   A slow moving warm front leads the
ushering of enhanced moisture and unstable air across the Hudson
Valley into the Lower Mohawk Valley, though much of the area
upstream remains quiet unstable with pockets of 2000-3000 J/kg
still remaining toward the end of day (greater further east into
the Mid-Atlantic).

Visible and 10.3 EIR loops show numerous clusters of thunderstorms
across the area; though as each has cycled and produced outflow to
support newer downstream generations; the broad southwesterly
steering upstream has brought some increased organization into
some SW to NE linear features through E OH/W PA into WV. Flow is
stronger having limited duration for initial
development/downdrafts, but with the component of alignment to the
mean wind, there are widely scattered incidents of short-term
training increasing duration to support localized 1.5- 2" totals.
Within the complex terrain that still remains fairly well
saturated, these localized totals may induce flash flooding given
hourly FFG over 1-1.5" and less than 2" in 3hrs; but may only
affect one or two watersheds/narrow valleys in the Allegheny
Plateau.

Further east, cell motions are a bit weaker being closer to the
apex of the larger scale ridge, though larger outflow boundaries
are being generated and interacting with Bay/Ocean Breeze or other
outflow boundaries to trigger newer/broader updrafts.  Storm
interaction may further slow forward motions resulting in
increased duration that may last for slightly greater than 1hr. So
spots of 2-3" are possible as 18z HREF suggests with 40-50%
neighborhood probabilities for 2" and 20-30% exist over
east-central PA into N MD.  As such, incidents of widely scattered
flash flooding remain possible through the late evening into early
overnight as instability slowly diminishes with loss of solar
heating.

Gallina

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

ATTN...WFO...BGM...BUF...CLE...CTP...ILN...LWX...PBZ...PHI...
RLX...

ATTN...RFC...RHA...TAR...TIR...NWC...

LAT...LON   42897624 42387504 41017468 40357465 39577591
            39247672 39057733 38647910 38208089 37738173
            37948231 38848362 40588259 41718137 42357991
            42657818