Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 220155

Area Forecast Discussion
National Weather Service State College PA
955 PM EDT Mon Aug 21 2017

High pressure moving off the Mid Atlantic coast will bring a
warm and increasingly humid southerly flow to the region into
Tuesday. A strong cold front will move through the region late
Tuesday and Tuesday night. Cooler and drier conditions will
return for the second half of the week.


Flat upper ridge in zonal flow with several weak shortwaves
aloft working on increasing deep layer moisture and moderate
instability to produce scattered coverage of showers and storms
through late this evening. Activity continues to weaken overall
but still some local heavy rainers over the lower Susq River
Valley early tonight.

Holding onto slight chc pops in most areas for the overnight
with additional disturbances working eastward from eastern OH
and deep layer moisture continuing to increase in weak boundary
layer convergence. Patchy fog expected especially over portions
of the Lower Susq. which have had persistent rainfall this
evening. Mins will range from the lower 60s north to the lower
70s southeast.


Warm humid day Tuesday. Some issues with the timing of the
showers in CAM verse none convective allowing models. Most
guidance suggest rain likely and some strong to severe storms
possible in the late afternoon/evening.

Timing in some CAMS implies earlier convection than non-
convective models.

The front should bring in much cooler weather Tuesday
night. But ahead of it Tuesday will be a warm humid day with a
good chance of showers and thunderstorms.


A strong cold frontal passage late Tuesday (NW PA)/Tuesday
night (SE PA) will be followed by a extended period of early
autumn-like weather for Wednesday into the upcoming weekend as
an anomalously deep sfc low/upper trough slides east across
southeastern Canada.

Daytime high temps will be about 5-7 Deg F below normal across
the Western Mtns on Wednesday, though still just slightly below
normal across the SE zones prior to the arrival of the
deeper/colder air for the latter part of the week.

GEFS mean 850 mb temps will dip about 2-3 deg C in all locations
for Thursday-Sunday, leading to max temps averaging 5-10 F
below normal (with min temp departures about 10-13F below
normal Friday-Sunday) as a large Canadian High Pressure area
pushes SE across the Glakes Region and becomes centered over the
NE states.

Lows Fri/Sat/Sun mornings with high centered overhead, will be
dipping into the l-m 40s over the Northern Mountains (and
deeper valleys of the Central Mountains) and solidly into the
50s elsewhere. Some of the perennial cold spots near and to the
east of KBFD could see readings of 38 or 39F.


Scattered to isolated showers and thunderstorms across Central
Pennsylvania at 22z. Most are exiting the Middle and Lower
Susquehanna Valley areas at this time, with a few more north of

Mainly VFR conditions for the rest of the day, except for
isolated restrictions in TSRA through about 01z.

Overnight, expect areas of MVFR fog to develop, with isolated
spots of IFR visibilities and ceilings.

Morning fog gives way to VFR conditions Tuesday, but widespread
TSRA expected during the afternoon and evening.


Tue...Patchy AM fog. Afternoon/evening TSRA impacts possible.
Wed...AM low cigs BFD/JST, otherwise VFR.
Thu-Sat...No sig wx expected.




NEAR TERM...Grumm/DeVoir
SHORT TERM...Grumm/La Corte
LONG TERM...La Corte/Lambert
AVIATION...Grumm/Jung is the U.S. government's official web portal to all federal, state and local government web resources and services.