612
AWUS01 KWNH 261938
FFGMPD
NYZ000-PAZ000-OHZ000-270000-

Mesoscale Precipitation Discussion 0503
NWS Weather Prediction Center College Park MD
336 PM EDT Wed Jun 26 2024

Areas affected...Northern Pennsylvania

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

Valid 261936Z - 270000Z

SUMMARY...Backbuilding convection running into a slow-moving warm
front that is near the PA/NY State Line may cause flash flooding
into this evening.

DISCUSSION...A strong front draped along the PA/NY state line is
causing strong lift along and south of the boundary this
afternoon. Numerous backbuilding thunderstorms have developed,
being fed by plentiful moisture and instability in the air mass
south of the front. SPC mesoananalysis shows SBCAPE values of up
to 3,000 J/kg across north central PA, being advected into the
front on southwesterly winds. PWATs in the air mass south of the
front are as high as 1.7 inches in northeast Ohio, whereas just
north of the front in the Finger Lakes region, PWATs drop to
around 1.1 inches. This tight gradient highlights the strength of
the front. FFGs going into this rainfall event across northern
Pennsylvania are between 2-2.5 inches/hr and 2.5-3 inches/3-hours.
These will drop with multiple rounds of heavy rain due to the
storms, so exceedance appears probable.

CAMs guidance going forward suggests the storms running into the
front will become a bit more progressive in their movement towards
the east, but also train along the front as they do so. This will
support a continued threat for flash flooding. There is good
agreement on this convective evolution playing out across
north-central Pennsylvania. By around 00Z this evening, the storms
across northeast Pennsylvania should consolidate more into a
north-south oriented line that tracks east into the Hudson Valley
as the trailing cold front over Canada (not shown) sweeps the
convection off to the east. By this point there should be minimal
training, so the flood threat should diminish into the evening.

Wegman

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

ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...

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

LAT...LON   42268002 42197934 42227946 42037905 42027773
            41937667 41757613 41087629 40917685 41147886
            41278049 41578089 41988091