Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 010111
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
811 PM EST Wed Nov 30 2016

.SYNOPSIS...
A large upper trough and pool of colder air will move across the
region over the next 12 to 24 hours. The cold air and westerly
winds may trigger snow showers in northwestern Pennsylvania. A
series of troughs in the west will slowly build a ridge over the
eastern US early next week. It should warm up again ahead of
another 500 mb trough and cold front later next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Large area of showers over central and eastern PA early this
evening in the relatively soupy 1.25"+ PW air mass that covers the
eastern third to half of central PA. Sfc cold front with NCFRB
slowly pushing through western PA evident on regional radar. 50+
kt 850 mb jet lifting through northern VA mnaintaining another
line of shallow convection approaching the DC metro from the west
at this hour. Brief moderate rainfall may impact the lower Susq
River Valley during the mid to late evening hours as this feature
intensifies and lifts northeastward as newly formed triple point
deepens and crosses the Pocono Plateau by 06z Thu. It appears
thunder will stay just south and east of my area..but there could
be a rumble or two near the MD border.

Cold front which will move across the area late this evening and
overnight. Mild air ahead of the front will be displaced quickly
after FROPA with temperatures falling through the 40s and into
the 30s. Rainfall will taper off to showers behind the front as
well. Under NW post frontal flow the showers will tend to favor
the mountains of the north and west.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
Area under trough and NW flow Thursday. This will bring plenty of
cloud cover but limited snow shower activity mainly in the higher
elevations. Where it does snow, accumulations will be light and
mainly confined to higher elevations. Temperatures will be much
cooler and closer to seasonal average.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
The cold air is in placed Thursday night and Friday. The 850 mb
temperatures are not impressive, in the -4 to -6 range. The colder
air and flow over the warm lakes should increase snow shower
activity in northwestern PA. Some guidance implies about -8C at
times. Most areas will be precipitation free Fri-Monday. Except
the northwestern areas where some LES is likely this weekend. The
more westerly flow is not as favorable for southwest mountains.
The GEFS/NAEFS/GFS have no QPF in southwest mountains. Focused
attention to minor LES snows in NW.

Late in the weekend and early next week the heights and 850 mb
temperature rise. Snow in NW should cut-off Saturday eve or early
Sunday. Then a slow and steady warm up is implied. High pressure
should be over us Sunday-Tuesday/Wednesday. Most areas will be
above 0C at 850 mb by Tuesday.

The issue in all the EFS is the potential cold air damming event
as the low moves into the Great Lakes. It may stay cooler in the
boundary layer Tue-Wed due to the surface high. The NAEFSBC and
GEFS imply this in the 2m temps and the 925 mb temps.

The always too wet GEFS biased our grids and has some warm
advection QPF by Monday. Any QPF would be very light. IF and only
IF there is precipitation there could be snow/rain-snow in
northern areas until overnight Monday into Tuesday. Rain farther
south and east. The GEFS and CMCE PWAT is close to normal with the
first two light QPF events. Not favorable for us to get rain.

Some more light QPF in the GEFS Tuesday so had chance rain showers
to slight chance again Tuesday. Not too confident in this still
weak pattern and low PWAT values

Our best chance for rain next week will likely be in the Thursday
timeframe when the cold front moves into the region. As forecast
it pulls about +1 sigma PWAT into our region. Thus, it may be the
best forcing mechanism. Thus the GEFS has the highest PDF based
POPS Wed into Thursday. We have over a week to deal with rain to
snow potential with that potential event.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Most of the steady rainfalls has ended for KBFD...KJST...KAOO and
KUNV. Farther east more rainfall and fog is possible this
afternoon. IFR will dominate most of this region until this
evening. We cannot rule out isolated thunderstorms in the extreme
southwestern Mountains and in the KMDT-KCXY-KLNS air space. Better
chance to the south and east this afternoon and early evening
hours. Be mindful of thunderstorms to the south and east.

The shallow cool air and warm air aloft is producing areas of
strong windshear.

The cold front comes through overnight and the rain moves to our
west. Improving conditions overnight with more MVFR and VFR.
Thursday should be a mostly VFR day. Isolated MVFR in western
mountains.

Outlook...

Thu-Sat...Sct SHSN w/ocnl MVFR/IFR in BFD-JST. Sun...Mainly VFR.
Restrictions still poss NW in the morning.

&&

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

&&

$$
SYNOPSIS...Grumm
NEAR TERM...Ross/DeVoir
SHORT TERM...Ross
LONG TERM...Grumm
AVIATION...Grumm/Ross



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