Area Forecast Discussion
Issued by NWS State College, PA

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863
FXUS61 KCTP 201607
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1107 AM EST Fri Jan 20 2017

.SYNOPSIS...
A weakening warm front will push across the state today.
Relatively mild but cloudy and unsettled conditions will
persist through the weekend before cooler air makes a return
next week.

A complex storm system is expected to move off the Mid Atlantic
coast Monday and Tuesday and could bring a return of wintry
weather.

&&

.NEAR TERM /THROUGH TONIGHT/...
11 am update...
Everybody is above freezing except one AWS ob in Mifflinburg.
The constant rain is now of of Somerset Co and moving steadily
NE. The band of rain seems just slightly ahead of schedule.
Behind it the clouds are lowering as the dewpoints push the
temps up. With only a light southerly wind this aftn, expect the
dank wx to continue into the night as well. Temps should
therefore move little overnight.

9 am update...
Have cancelled the advy as temps are warming as the rain moves
in. Only very isolated pockets of zr are possible, but trend is
exactly on track with prev fcsts.

Prev...
A weakening warm front extends from northern KY eastward
through southern Va. Milder air is making progress northeastward
bringing a shield of rain along with it.

Guidance suggests the rain will overspread the region around or
shortly after sunrise. The biggest issue with the advance of
the rain is whether surface temps rebound enough to prevent a
period of freezing rain. Latest HRRR is colder and shows spotty
Freezing rain along the leading edge as the rain progresses
northeast. Being the hours of the morning commute, we have
issued an Advisory for a few hour period of freezing rain to
cover the possibility of some light icing.

The precip will continue off to the northeast with improving
conditions expected for the afternoon as the steady rain turns
to just scattered showers.

As we have seen so many times this season, the low level cold
air will be stubborn to dislodge, so while it will be quite mild
over SWRN Pa today, the ridge-valley area of central Pa will
stay locked in with temps only in the upper 30s to mid 40s.

With just some scattered showers early tonight, the overnight
temperatures will stay steady or only fall back slowly as we
become ensconced in a mild SW flow between high pressure over
the Mid Atlantic and a stronger low moving through the upper
Midwest. Lows in the 30s and 40s will be some 15-25 deg above
normal for the dead of winter.

&&

.SHORT TERM /SATURDAY/...
Saturday will be mild with a fair amount of cloudiness, but
mostly rain free. I cannot rule out a stray shower, especially
over the NW, but the chances are very low and I chose the more
optimistic forecast not mentioning rain.

Highs will average in the 40s and 50s, well above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The upper ridge is forecast to re-establish itself over the
eastern U.S. early in the period, as a very complex storm
system gathers over the southern Rockies by Saturday evening.
This southern stream low is tracked through the southern states
before turning northeast over the eastern US early next week.
Meanwhile the models build high pressure over eastern Canada and
gradually ooze colder air south into the NERN US.

By late Monday into Tuesday morning, the parent upper low is
made to track into the Mid Atlantic states. The deterministic
GFS has the southernmost track, through eastern NC then up just
off the coast. The GEFS has a slightly more northern track
through VA.

The ECMWF and its ensemble partner are more north taking the
storm up through eastern PA. The ECMWF tracks its sub 990mb
surface low through the Del Marva up along the NJ coast is what
we look for as a "sweet spot" for snowstorms locally.
Temperatures are marginally cold so it`s still questionable what
the precip type will be. But it`s the most interesting pattern
we have seen this winter for the snow-birds among us.

After our early week storm system, the eastern ridge is made to
make a rapid rebound, even if for just a short time around
midweek. A fast moving shortwave quickly chews the top off the
ridge we are made to evolve into a cyclonic westerly flow by
week`s end. It will turn cooler, but not especially so as there
really is no truly cold air over North America at the current
time.

&&

.AVIATION /16Z FRIDAY THROUGH TUESDAY/...
The steady rain now covers all the terminals except KJST where
it has pushed to the NE already. However, the light srly wind
and increasing dewpoints will lower the cloud deck in most
places after the constant rain ends. The only clearing might be
in the SE, but the L/IFR clouds, fog, and dz look to be rather
widespread.

Some improvement should occur on Saturday - mainly in the SE -
with meager mixing, but wind still very light. The next big
thing will be working up over the MS and TN valleys over the
weekend and start to throw a surge of moisture north into the
Mid-Atlantic. Some rain is expected to move in later Sunday,
mainly across the south.

Looks like Monday and Tuesday will be wet days.

Outlook...

Sat...L/IFR CIGs and fog likely, mainly in the morning.

Sun...IFR/MVFR CIGs likely. Rain advances fm S-N.

Mon...Rain/low CIGs likely with snow possible central Mtns.

Tue...AM rain/snow and low CIGs possible.

&&

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

&&

$$
SYNOPSIS...Dangelo/La Corte
NEAR TERM...Dangelo/La Corte
SHORT TERM...La Corte
LONG TERM...La Corte
AVIATION...Dangelo/Martin



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