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Area Forecast Discussion (AFD)

Issued by State College, PA (CTP)

FXUS61 KCTP 251451

Area Forecast Discussion
National Weather Service State College PA
1051 AM EDT Mon Mar 25 2019

Low pressure over southern Indiana will track south of
Pennsylvania late today. 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.


Radar loop at 1440Z shows weak showers beginning to clip the 
Laurels as the parent shortwave and best forcing shifts east of 
the state. The large upper level low continues to open up into a
deep trough. That trough will move from the Tennessee valley 
eastward. The boundary extending from that will bring showers to
the Laurel highlands this afternoon and evening. Latest 06Z GFS
brings 0.5-0.75 inches to the Southeast corner of the region 
with the heaviest amounts expected This afternoon into the early
evening hours. Due to the warm air advection out ahead, the 
P-type should be rain though can't rule out snow in the higher 
elevations. Have increased snow for the mountains in Somerset 
and Cambria counties, mainly at elevations above 2000ft. Surface
temperatures appear to be the limiting factor for any 
accumulations, but wouldn't be completely surprised if an inch 
or so was reported on the highest ridgetops south of the 

After a cloudy start, surface ridging and much drier air mass 
building in from upstate NY should result in mostly sunny skies
across northern Pa today, while model RH profiles indicate overcast
conditions all day in the south.


Light showers could linger through the southeast through the 
early evening hours. Clearing skies will advance south tonight,
as low pressure passes off the coast and high pressure builds 
south from NY state.

Canadian high pressure will build into the region Tuesday,
accompanied by abundant sunshine and a light northerly breeze.
Mixing down model 850mb temps yields expected max temps ranging
from the upper 30s over the northern mountains, to the mid 40s
across the Susq Valley.


Med range guidance continues to support a high confidence of
fair weather through midweek, as Canadian high pressure drifts 
southeast over the area. Nearly ideal conditions for radiational
cooling Tuesday night with high directly over the area, so have
leaned toward the colder Eco and MAV MOS over the NBM min temp

Med range guidance all indicating a dying cold front will either
approach or push into northwest Pa late Thursday into Friday,
accompanied by a chance of showers. Both the 00Z ECENS and
operational EC/GFS suggest the front lifts north of the region
late Friday and Saturday, as wave of low pressure forms over 
the Miss Valley and tracks northeast through the eastern Grt 
Lks. All guidance continues to suggest the best chance of 
showers comes next weekend, when east coast ridge breaks down 
and cold front pushes across the state. 

Above normal temperatures appear very likely Thu-Sat in the 
deep southwest flow between east coast ridge and approaching 
front. A transition to drier and colder conditions appears 
likely Sunday, as the front pushes east of the state.


VFR conditions continue to prevail across the region this
morning, save for KJST where low level moisture and the upslope
flow into the mountains is producing MVFR ceilings. Latest radar
imagery shows spotty light precipitation moving east.

Later this morning, a weak wave will slide south of the airspace
bringing light rain into the southern half of the region. 
Models generate limited moisture with this feature as it 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.


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.


A weak weather system will move south of the state today through 
tonight producing light precipitation, mainly over the southern 
half of the district. Behind this system, a large area of high 
pressure will build across the eastern third of the country 
through mid week. 

***This area of high pressure contains very dry air, with
 dewpoints in the single digits expected today, Tuesday and
 Wednesday across the northern half of the district. Dewpoints in
 the teens are forecast across the southern half on Tuesday and
 Wednesday. This will result in afternoon relative humidity below
 30 percent all three days. Given sufficient mixing, quick drops
 to below 20 percent are possible in some locations.

Winds are expected to remain on the light side /less than 10mph/ during
this period.




NEAR TERM...Fitzgerald/Ceru
SHORT TERM...Fitzgerald/Ceru
LONG TERM...Fitzgerald