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FXUS61 KCTP 150655

Area Forecast Discussion
National Weather Service State College PA
155 AM EST Sun Dec 15 2019

Cooler air will wrap through Pennsylvania tonight as low 
pressure lifts north of the region. An area of low pressure 
originating over the southern plains will track northeast into 
the Mid Atlantic region late Monday and early Tuesday.


A tightening gradient will result in increasingly gusty west 
winds across much of the forecast area overnight. Bufkit 
soundings indicate there will be frequent gusts to near 30kts.
The exception to the gusty winds may be over the Lower Susq
Valley, where breaking clouds will lead to less effective mixing
and lighter winds. 

Over the Allegheny Plateau, orographic forcing will keep
scattered snow showers in the forecast. Satellite imagery and
near term models indicate cloud tops will be marginally cold
enough to support snow, so have included the possibility of a
bit of fzdz in addition to scattered snow showers. Any additional
snow accumulations between 06Z-12Z should be generally less than an


Sunday should be a blustery day, as region will remain under the
influence of intense storm system lifting into Quebec. Model
soundings support gusts around 30kts through much of the day. 

Approach of high pressure and lowering inversion heights should
cause lake enhanced, orographic snow showers/flurries over the 
western mountains to gradually diminish today. Any additional 
accumulation will be less than an inch. Subsidence to the lee of
the Appalachians should result in a decent amount of sunshine 
today across the southeast part of the forecast area.

Mixing down model 850 temps between -10C and -5C yields expected 
max temps from around 30F over the high terrain of western Pa, 
to the low 40s across the Susq Valley.


The bulk of medium range guidance tracks surface low associated
with southern stream wave along the Mason Dixon Line late Monday
into early Tuesday. NBM thermal profiles support an initial
period of snow, a period of wintry mix/freezing rain, and a
final change to rain over much of the area. Have trended 
snowfall totals down in favor of freezing rain. Temperatures may
remain cold enough for a wintry mix and no changeover to 
freezing rain along the northern tier even as waa ramps up 
Monday night. Although the surface low is not progged to be very
deep, this system will be drawing copious Gulf of Mexico 
moisture northward. All guidance currently supports potential 
precip totals of around 1 inch across southern Pa, the bulk of 
which should fall as rain, with a stripe of light to moderate 
snow accums across the northern tier. As the low pressure system
moves east, lake effect snow will kick in once again bringing
light accumulations to the NW mountains.

Below average temperatures and generally dry weather will settle
in for the second half of the week, as an upper trough swings 
through the northeast conus.


IFR cigs continue across all the central and western TAF sites.
Vsbys at BFD and JST are MVFR with VFR vsbys elsewhere. The 
Prevailing west- northwesterly flow will persist through Sunday 
afternoon. Gusty surface winds at the south central airports 
may produce LLWS through early Sunday. Mainly at JST and AOO. 
Scattered IFR cigs and scattered snow showers expected at BFD 
through 09Z. IFR cigs will persist at BFD and JSt with gradual 
improvement to MVFR by Sunday afternoon. 

East of the mountains, downsloping subsidence should bring 
partial clearing tonight, with a return to MVFR over the central
mountains and VFR for the SE.


Mon...PM low cigs/wintry mix possible.

Tue...Low cigs NW, improving conditions elsewhere.

Wed...Restrictions likely north/west with snow showers.

Thu...No restrictions expected.





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