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FXUS61 KCTP 121552

Area Forecast Discussion
National Weather Service State College PA
1052 AM EST Thu Dec 12 2019

Fair weather pattern today will turn stormy Friday through the
weekend with risk of ice, heavy rain, and lake effect snow. 
Temperatures will trend milder into Saturday before gusty winds 
direct colder air back into the region by Sunday. Winter weather
threat continues for Monday into Tuesday with the potential for
snow and ice accumulation.


Little to no change to the current forecast through this 
evening. After a cold start with single digit lows in the
northern tier, expect plenty of sunshine this afternoon with 
highs rebounding into the upper 20s to upper 30s (about 5 
degrees below average on the whole). High clouds should thicken 
across western PA by late evening. 


Interesting and challenging system moving in from the south -
and a little from the east - later tonight and Friday. Temps
should cool off into the m-u20s at first tonight. Then there is
a llvl easterly flow develop into the sern counties and 
Poconos with the cold air damming showing up nicely. This
easterly flow brings with it some moisture trapped under the 
inversion. The HREF members and NAM are most bullish on the 
patchy QPF in the east before any more- widespread rain would 
arrive later in the day. This could lead to some patches of 
DZ/FZDZ in the east, esp on the ridges before sunrise. QPF thru 
15Z would be very light (just a couple of hundreths at most) 
there. So, there is the possibility for a little bit of ice to 
form on things. But, this 00Z guidance seems to be the first 
widespread indication of this occurring. A leveling-off or even
a bit of a rise to temps may occur later tonight with mins just
5-6F lower than the maxes from today.

Sub-freezing air takes a while to shrink from the outside in on
Friday during the day. Thanks, topography and high pressure to
our NE.

The arrival of better forcing is later in the day, or even not
until closer to midnight Fri night. Rain may be rather patchy on
Friday, with no sig QPF until after sunset. So, while there is 
still a threat of temps staying below freezing on the ridge tops
of the central and western mountains, I am still not confident 
enough to post an advy at this point. Collaboration with 
neighboring offices resulted in similar thoughts from them.

The main rain will be Fri night and Sat as the sfc low goes
right overhead. It should be mild enough after sunset to keep it
all liquid.


*Heavy rain possible (1-2 inches) in east-central PA Friday
 night into Saturday 
*Period of snow/mixed precipitation likely later Monday into
 Tuesday; potential for winter weather should be monitored

Low pressure system will draw deep moisture/above normal PW 
northward into the area Friday night resulting in widespread 
moderate to briefly heavy rainfall. Storm total rainfall of 1 
to 1.5 inches is forecast across east-central PA. Will need to 
watch for a transition back to snow on the backside of the 
system as the upper low pivots into the Northeast and gusty 
northwest flow ushers cold air back into the region. Lake effect
snow accumulation is likely in the favored upslope high terrain
and snowbelts Sat night into Sunday. Temperatures trend colder 
Saturday to Monday as the active pattern briefly takes a pause.

Winter weather threat will need to be monitored for early next 
week with the potential for snow and ice to impact the area 
later Monday into Tuesday. Updated local winter storm outlook 
graphics on the web and HWO to reflect the latest trends/probs.
Below average temps are forecast into the second half of next


High pressure building into the region will ensure VFR 
conditions and light wind through this evening. 


Fri...Rain/low cigs likely, especially late.

Sat...Rain/low cigs likely, especially early. Windy late.

Sun...Gusty west wind. AM low cigs/snow showers possible W Mtns. 

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





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