Area Forecast Discussion
Issued by NWS State College, PA

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509
FXUS61 KCTP 021147
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
647 AM EST Fri Dec 2 2016

.SYNOPSIS...
A large and deep storm system will move slowly through Quebec over
the next couple of days keeping a prolonged period of cool
northwest flow over the local area. High pressure will build in
for a brief time Sunday before the next frontal system approaches
early next week.

&&

.NEAR TERM /UNTIL 7 PM THIS EVENING/...
Temps will rise little over much of the area due to extensive
cloud cover, neutral temp advection, and good mixing in lower
layer of atmosphere. With the temps at or above freezing everywhere,
the light and quick-moving precip across the north is likely to
not stick much at all. The little heating we do get today and the
downslope flow will be enough to push the temps in the SE into the
m40s. However, the NW half of the area will stay below 40F. Most
likely precip type is snow/snow grains/snow pellets judging by the
cloud and sub-cloud temp profile. Despite light precip falling for
much of the day in the NW third of the CWA the surface temps
should allow for little if any accums through the daylight. Have
continued with a bare mention of snow accums in the NW.

&&

.SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SATURDAY/...
The stacked low pressure over Quebec gradually moves into the
Canadian Maritimes. The flow off the lakes will be highly
persistent with lake effect precip expected to last into Sat
Night. A weak/subtle feature will slide across the lower lakes
this evening/early tonight, and could briefly enhance the snow
rates and push snow bands into the central mountains. Tonight is
the most likely time for any kind of accums to occur. However,
only about half of the area goes below freezing. The wind does not
slacken and the clouds will be pesky. Thus, the temps will not get
more than 6 to 10F colder than daytime temps. Saturday looks like
much of the same. Second verse same as the first. Have inched the
temps up a little higher than guidance in the SE where the
downslope could help them out. Still, these numbers are within a
few degs of normals for the first part of Dec.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Sunday brings a brief respite as high pressure moves over the
state. Sunday evening and night, a period of light snow is
looking likely as a northern stream shortwave races through the
region with a burst of warm advection. QPF looks to be on the
order of a tenth of an inch or less, but occurring overnight many
places could see their first coating of snow of the young season
by Mon morning. Snow is more likely in the NW than SE.

Another ridge moves through on Monday as progressive weather
pattern becomes more active. On Tues there is decent agreement in
bringing the SW US upper low up through the Ohio Valley as a
shearing out shortwave and diffuse surface low. Unless cold air
damming traps enough chilly air in the low levels to make for some
freezing rain, the precip type with this midwest system looks to
be mainly rain.

The end of the week brings some model disagreement with the
GFS/GEFS being faster than the ECMWF with the next large upper
trof and frontal system. Either way, precip looks like a good bet
around the Thu/fri period as all solutions eventually bring this
trough through. So predictability is increasing, but timing issues
remain. Best bet for precip at this point is mainly rain over the
SE as decent push of warm air lifts ahead of the system, with a
rain/snow mix further north where warm air will not infiltrate as
much.

Behind the trough, looks like a chilly weekend in store with a
potential sharp dropoff in temps.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
Early AM satellite loop shows stratocu covering most of Central
Pa associated with slow moving low pressure over Southern Quebec.
Cold air flowing over Lk Erie is producing lake effect snow
showers across Northwest Pa. Upstream radar imagery and latest
GLMP MELD supports predominantly IFR conditions at KBFD for the
balance of the morning. Elsewhere, model soundings indicate
falling CIGs this morning, as a slight wind shift from WSW to WNW
causes moisture from the Great Lakes to spread south. GLMP MELD
suggests IFR CIGs and snow showers are possible later this
morning at KJST. Downsloping flow east of the mountains should
result in progressively better conditions further east, with tempo
MVFR possible at KAOO/KUNV and VFR at KIPT/KMDT/KLNS.

Weak diurnal heating/mixing should result in a modest increase in
CIGS by this afternoon, likely resulting in CIGS between 1-2KFT at
KBFD/KJST and VFR elsewhere. However, passing snow showers will
still occasionally drop vsbys below 3SM at KBFD/KJST through
evening.

The entire region will continue to see breezy conditions last
through the next 24 hours. Clearing skies have resulted in lighter
winds at KMDT/KLNS early this morning. However, Bukfit soundings
support winds between 10-20kts across the entire region later
today and evening, with occasional gusts near 25kts.

Outlook...

Sat...SHSN with ocnl IFR vsby at KBFD/KJST, mainly in the morning.

Sun...Light snow/reduced vis possible at night, mainly NW Mtns.

Mon...No sig wx expected.

Tue...Mixed precip/low CIGs possible.

&&

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

&&

$$
SYNOPSIS...Dangelo/Gartner
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...La Corte/RXR
AVIATION...Fitzgerald



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