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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

                            
000
FXUS61 KCTP 250649
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
249 AM EDT Mon Mar 25 2019

.SYNOPSIS...
An upper low over the Miss Valley will weaken as it pushes east
and merges with a shortwave diving southeast across 
Pennsylvania Monday. Canadian high pressure and associated dry
air mass will settle south across the area during midweek. A 
cold front is then likely to push southeast across the region 
next weekend.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
Radar loop at 0630Z shows showers developing over western Pa
in advance of a cold front entering the northwest part of the
state. The front and parent northern stream shortwave will push
southeast across the region early this morning. Moisture return
ahead of front is not that impressive overall, but best across 
southwest Pa. Thus, placed the highest POPs of around 60 pct 
across the Laurel Highlands, where orographic enhancement 
expected, and only around 20 pct POPs across the east of the
mountains and south of I-80. By dawn, expect the front to have
settled south of the forecast area and the showers to have
dissipated due to passage of shortwave.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH 6 AM TUESDAY/...
The remnants of Miss Valley upper low and associated surface 
low are progged to track south of Pa later today. The latest 00Z
operational models and HREFV2 are supporting increasing 
confidence in the southern tier of the state being impacted by a
period of light rain, beginning around midday and lasting until
early evening. An examination of model soundings indicates 
some wet snow is likely over the high terrain of southern Pa, 
mainly at elevations above 2000ft. Surface temperatures appear 
to be the limiting factor for accumulations, but wouldn't be 
completely surprised if an inch or two was reported on the 
highest ridgetops south of the turnpike. 

Surface ridging and much drier air mass over upstate NY should 
result in mostly sunny skies across northern Pa today, while 
overcast conditions look likely in the south.

Clearing skies will advance south tonight, as low pressure 
passes off the coast and high pressure builds south from NY
state. 

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
The axis and SWWD extend of an upper trough over southeastern
Canada and deepening cold air will extend across PA Monday
night. At the same time, the northern extent of light precip 
(from a weak sfc low and southern stream trough) will brush our
southern zones and will transition into a light rain/snow mix 
for a short period prior to ending by 04Z Tuesday. No snow accum
is expected as sfc temps will be in the mid to upper 30s. 

NW flow aloft and dry conditions with below normal temps will
follow for Tuesday, with strongly anticyclonic flow/subsidence 
at llvls. 

The NW flow aloft will abate for midweek as a large area of sfc
high pressure builds across the Commonwealth. Mainly clear 
skies are expected for later Monday night right through 
Wednesday.

A slow-moving frontal boundary, draped to our northwest across 
the Grt Lks, may sink SE into the region Thu night or Friday 
before stalling out as a weak northern stream trough slides 
from the Upr Glakes to the Canadian Maritimes. 

A deepening upper trough and 1000 mb sfc low over the Central 
Plains and Mid Miss Valley respectively late Fri Night/Sat will 
lead to a quickly expanding rain/snow field from the Central 
Plains to Upper Glakes, with a building ridge along the East 
Coast keep us very mild and mainly dry under south-southwest 
flow at the sfc and aloft.

Near to slightly above normal temps are forecast for Wed under
the central of the high. Afterward, temps will rebound to 7-10F
above normal Thursday, and peak at 15-18F above normal Friday
and Saturday. 
 
Will maintain a chance of showers across northwest Pa late in 
the week through Saturday to account for model differences with
regard to the exact location of the quasi-stationary/warm front
that's expected to stretch from Lake Erie NE across the St.
Lawrence Valley.

The greatest prob for rain showers comes for later Sat and
Saturday night, when east coast ridge breaks down and a cold 
front pushes across the state. Above normal temperatures should
hang on Sat before dropping back to near normal for Sunday with
scattered rain/snow showers possible across the Mtns and
isolated-sctd rain showers in the Valleys.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
VFR conditions continue to prevail across the region tonight. A
cold front over central New York will slip southward through 
Pennsylvania during the overnight hours. A shift to northerly 
winds will accompany the frontal passage. While actual 
precipitation will be spotty overnight, increasing low level 
moisture and the upslope flow into the mountains will likely 
generate some MVFR ceilings.

On Monday, a weak wave will ride eastward along the front, which
should be south of Pennsylvania. Models generate limited
moisture with this feature as is is sheared, but threat exists
for some light precipitation and ceiling restrictions across the
southern tier during the day.

High pressure will then prevail through Thursday, with a frontal
system approaching for Friday.

.Outlook...

Mon...AM rain/snow. Restrictions possible, mainly northern and
western mountains.

Tue-Thu...No sig wx expected.

Fri.....VFR, but with some scattered showers possible northwest.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...Fitzgerald/La Corte
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Fitzgerald/Lambert
AVIATION...Jung