Area Forecast Discussion
Issued by NWS State College, PA

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614
FXUS61 KCTP 220316
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1116 PM EDT Tue Mar 21 2017

.SYNOPSIS...
Look for a relatively short-lived but significant change in the
weather later tonight and Wednesday as a frontal system brings
much colder air back to the region for Wednesday and Thursday.
A period of ice or wintry precipitation is possible immediately
ahead of warm air which will return late in the week. A milder
pattern will persist through the weekend with opportunities for
rain into early next week.

&&

.NEAR TERM /UNTIL 8 AM WEDNESDAY MORNING/...
High clouds from the wave rolling to our south are thinning
already. lower clouds bubbling up across NY and just starting
to sneak into PA. Hardly anything on radar. Thought about just
pulling mentions of a coating in the north and just going to
plain ol` flurries. But, the POPs are very low (30 or less) all
night. Can`t really argue against a dusting, so I`ll leave it
alone. Hill-top wind chills will be near zero. At least most of
the snow has melted away and blowing/drifting snow is not
possible.

Prev...
Dewpoints had crashed into the single digits along the NY
broder but have recovered slightly thanks to some decoupling.
However, the wind will be rather strong all night. Cloud cover
over the south and the development lake-induced clouds in the
north could help to keep temps up just slightly from what we
have running right now.

Prev...
Big temperature changes later this evening as strong cold front
will push across the region. The front will bring gusty winds
but will be mainly dry with just a few mainly light snow
showers over the usual spots in NW PA. A short northerly fetch
and dry air should limit any accumulation to a brief coating
over Northern Alleghenies.

&&

.SHORT TERM /8 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
It will be cold with a good deal of the area not breaking
freezing /15-25 degrees below average/. A strong ridge of
surface high pressure will build into the area with decreasing
winds and clear skies by afternoon. This will set the stage for
strong radiational cooling and very cold temperatures by
Thursday morning.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
WAA pattern quickly follows what could be winter`s last gasp
with moderating temperatures into the second half of the week.
Models indicate risk for snow/ice mix ahead of the warm air as
pcpn spreads into retreating shallow low-level cold layer
(associated with 1035mb high pressure area that briefly pauses
along the coast) Thursday night-AM Friday. Max POPs are over
the NW 1/3 of the area based on a multi-model consensus blend
but ZR risk extends into the interior zones based on WPC
probabilistic winter pcpn guidance.

Risk for mix/ZR continues into mid Friday morning before
temperatures warm above freezing. Models continue to show the
warm front lifting north into NY by Friday night, becoming
quasi-stationary and setting up a west-east oriented baroclinic
zone. Location of this boundary will be key as it will be a
focus for pcpn into the weekend.

Models and ensembles are in decent agreement with the general
synoptic pattern evolution across the CONUS with a series of
upper troughs moving into the Southwest U.S. and losing
amplitude as they eject/dampen out downstream across the Central
Plains and east of the MS River. The lead wave and associated
frontal system is progged to reach the area by Sunday which
coincides with max POPs based on NBM/WPC/ECENS blend.

The first wave will plow the path for a weakening second wave
lifting through and bringing chances for showers early next
week - though by then precip type looks to remain plain rain.

Above average temperatures are expected over the weekend with
the warmest day likely on Saturday with some sites approaching
70F over southern PA. Sunday should also be mild but a bit
cooler due to likelihood of rain. Operational EC/GFS/CMC are
somewhat at odds early next week with EC/CMC more bullish than
GFS with shallow cool air to seeping southward east of the
Appalachians.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
No large changes to the 03Z TAFS.

Earlier discussion below.

Strong cold front to the northwest, weak system over Ohio
moving east, and severe strorms over the south. There could
be a few lower clouds and light snow showers late at BFD and
JST, mainly due to dynamics, but moisture is limited. Not
expecting the 3 systems to combine into anything major
over central PA.

Did cut back on lower clouds late, for 00Z TAF package.

Wed should be mainly VFR after mid morning, as very low
dewpoints work in. Gusty northwest winds.

More in the way of adverse weather for Friday, into next
week, as a cold front remains nearby, and split flow keeps
colder air to the north, and moisture from the south nearby.

Outlook...

Thu...No sig wx expected.

Fri...Showers/reduced CIGS possible, mainly BFD.

Sat-Sun...Showers/reduced CIGS possible.

&&

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

&&

$$
SYNOPSIS...Ross/Dangelo
NEAR TERM...Ross/Dangelo
SHORT TERM...Ross
LONG TERM...RXR/Steinbugl
AVIATION...Martin



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