583
FXUS61 KCTP 230159
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
859 PM EST Wed Jan 22 2025

.SYNOPSIS...
*A weak clipper tracking north of PA will bring increasing
 cloud cover to the Commonwealth this evening and into Thursday.
*Lake effect and upslope snow showers possible beginning late
 Thursday and into Friday, brining generally light accumulations
 topping out across northwestern Pennsylvania.
*Temperatures trend towards average this weekend and into the
 beginning of next week.

&&

.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
Surface ridging along the Mid Atlantic coast will provide
Central PA with fair and cold conditions tonight. Expect varying
amounts of mid level cloudiness associated warm advection
preceding a pair of mid level vort maxes lifting through an
upstream trough.

Mostly clear skies, light wind and fresh snow cover will result
in the most efficient radiational cooling across Southeast PA,
where we have nudged min temps a bit below NBM guidance. More
persistent cloudiness and a more active southerly breeze should
hold readings up a bit across the N Mtns. Expect min temps in
the lower single digits across much of the forecast area, but
the coldest rural valleys of South-Central PA are likely to dip
into the 5-10 below zero range.

&&

.SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
A marked warmup is anticipated Thursday, as a southwest flow
develops between the surface ridge off of the East Coast and an
upstream cold front over the Grt Lks. See no reason to deviate
from NBM max temps, which are in the 20s.

The bulk of model guidance points to mostly sunny skies for much
of Central PA Thursday, as the strongest mid level warm
advection lifts north of the PA/NY border. RH timesections
then indicate clouds arriving from west to east late in the day
ahead of the approaching cold front. Model soundings indicate
the return moisture ahead of the front will be shallow, but
could support a bit of very light snow where the WSW flow is
forced to ascend the Allegheny Plateau Thursday evening.

Large scale subsidence behind the exiting cold front should
result in mainly dry conditions Friday. However, veering
boundary layer flow should result in scattered lake effect snow
showers over the NW Mtns. Low inversion heights and a mainly
frozen Lk Erie should keep accumulations minimal. Model qpf
supports total snowfall Thursday PM through Friday ranging from
a dusting over most of the Allegheny Plateau, to perhaps 2
inches in the snowbelt of Northwest Warren County. Any snow
showers should end Friday night, as surface ridging builds into
the state and boundary layer flow shifts to the southwest.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Large scale flow pattern supports clippers dropping southeast
across the Great Lakes next week. The warm waters of the Great
Lakes will likely result in high centers splitting into two
sections, with the coldest air staying north of the lakes. Thus
we will see temperatures closer to normal. With the overall
pattern and snow cover, will be hard to see any extended mild
snaps.

Upper level troughs and wind shift lines will support some snow
showers from time to time into late Sunday, mainly across the
far northwest.

A clipper dropping southeast by mid week may support more snow
a bit further east and south.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
Scattered to broken clouds are continuing to stream in from the
west as of 0Z. VFR conditions are expected to continue for the
rest of tonight and through the day tomorrow. Mid and high
clouds will increase in coverage during the evening as warm
advection increases ahead of a moisture- starved disturbance
approaching from the west. Model soundings suggest that much of
this cloud cover will dissipate during the day on Thursday and
partly cloudy to mainly clear skies are expected after 12Z.

Winds will shift to the west-southwest Thursday afternoon which
will lead to clouds developing at BFD and JST. Moisture will be
very limited, at least initially, so not expecting any snow
showers prior to 18Z. Model RH profiles do suggest that lower
ceilings develop during the late afternoon and a few lake effect
and upslope snow showers could lead to visibility restrictions
at BFD and JST into the evening. A mention of PROB30 snow
showers has been included for BFD between 19Z and 21Z with
light snow and lower ceilings likely towards the end of this
forecast period.

Outlook...

Thu Night...Restrictions possible at BFD and JST with -SHSN.

Fri...MVFR/IFR conditions possible with -shsn in northern &
western PA mainly during the day.

Sat...VFR/no sig wx.

Sun-Mon...MVFR in -shsn possible in northern & western PA.

&&

.CLIMATE...
A record low temperature of -11 degrees was set at Altoona, PA
last night. The old record was -5 degrees set in 1984.

A record low temperature of -11 degrees was set at Johnstown,
PA last night. The old record was -9 degrees set in 1984.

A record low temperature of -18 degrees was tied at Bradford,
PA last night. The previous record low temperature date was
2022.

Record low maximum temperatures for January 22:

Harrisburg    14F in 2014
Williamsport  14F in 1961
Altoona       10F in 2014
Bradford       6F in 2014
State College  7F in 1936

&&

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

&&

$$

SYNOPSIS...NPB
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/NPB
LONG TERM...Martin
AVIATION...Bauco/Bowen
CLIMATE...Steinbugl