000
FXUS61 KCTP 231405
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
905 AM EST Sun Jan 23 2022

.SYNOPSIS...
A milder westerly flow of air returns to the region tonight as
high pressure slides off of the eastern seaboard tonight. The
first of a pair of Alberta Clippers approaches the area on
Sunday, spreading clouds and some light snow to parts of central
Pennsylvania later Sunday and again late Monday and Tuesday.
Temperatures will moderate a bit more on Tuesday, before
another cool down Tuesday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
Much of central PA in a dry slot early at mid morning as mid to
high clouds peal off to the east into NJ and NY, and upstream
clouds lower and thicken heading into the NW Mountains as WAA
increases ahead of approaching clipper low. Expect thickening
clouds from W to E through the remainder of this morning, with a
good deal of sun before that happens across the central and
southeast counties. Focus for later on remains on the
approaching Alberta Clipper, which is progged to track east
along the Mason Dixon Line between 22Z- 04Z. Typical of
clippers, this system lacks significant moisture, and we
anticipate only a light snowfall overall. Studying model time
cross sections of omega/DGZ juxtaposition indicates close to
cross hair signature for several hours this evening in the max
warm advection period, which may maximize snow accumulation
efficiency of the meager QPF that does manage to fall out.
Fairly high snow/water ratios, with maximum lift occurring
within or twoards the top of the dendritic growth zone, supports
greater than 15:1 snow:water ratios; the latest mean WPC
snow/water ratios are near 18/1.

High resolution model 850-700mb fgen fields, correlating well
with the heaviest snow currently falling over the midwest into
the Ohio Valley, indicate the corridor of steadiest snow will
reach the I-80 corridor late this afternoon and early evening.
Latest HREF mean qpf in this region is around 0.1 inches,
supporting a band of around 2 inches of snow along I-80.
Orographic enhancement is likely to result in amounts around 3
inches along the spine of the Appalachians, but coverage still
does not support an advisory.

Elsewhere, weaker forcing is indicated over the Lower Susq
Valley, where POPs are significantly lower and any snow accums
will likely be limited to a dusting. As for timing, near term
model guidance indicates the light snow will develop first
across the northwest mountains during the late morning hours,
then rapidly overspread much of central Pa during the early
afternoon.

High pressure building in behind departing clipper should
result in clearing skies and a diminishing breeze late tonight.
The fresh coating of snow should result in close to ideal
conditions for radiational cooling across the northwest
mountains, where position of ridge early Monday morning supports
calm winds. Have therefore undercut NBM min temps across the
northwest half of the forecast area. Latest RAP indicates lows
of 5-10 below over the northwest mountains, but not confident
enough to go that far below guidance at this time.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
Model RH profiles support a bright start to Monday under surface
ridge. However, increasing clouds are expected by afternoon ahead
of next clipper lifting across the Grt Lks. The surface low and
best forcing is progged to track north of Pa Monday evening.
However, passage of low level jet and associated warm advection
should support a period of light snow, focused mainly across
the northwest mountains, where ensemble mean qpf supports a
couple inches of accumulation.

Light, lake-enhanced, orographic snow showers are likely to
linger into Tuesday morning across the Alleghenies, as cold
northwest flow pours across the Grt Lks behind trailing cold
front. However, some very dry air crossing the lakes and low
inversion heights suggest any accums will be very light.

In contrast to recent days, GEFS 2m temp anomalies suggest
highs Tuesday will be near seasonable, ranging from the mid 20s
over the northwest mountains, to the upper 30s in the Lower Susq
Valley.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A reinforcing shot of arctic air will filter into the area
Tuesday night into Wed behind the departing front. Northwesterly
flow should generate the usual lake-effect and upslope snow
showers across the north and west. Temperatures will bottom out
Wed night, as clear skies and diminishing winds set the stage
for ideal radiational cooling conditions. Lows could dip below
zero once again across northern and western PA, perhaps rivaling
the cold we experienced Saturday morning.

After a cold Thursday, temperatures should begin to moderate by
week`s end ahead of an approaching clipper system. Global models
continue to hint at the potential for a coastal storm next
weekend in January, but considerable uncertainty and run-to-run
variability remains. Regardless, cold air will likely stick
around into the beginning of February.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR and borderline MVFR conditions over western and central
airfields with VFR in the Susq Valley at the 12Z update. These
will be the best conditions of the day, as things will slowly
deteriorate as the snow system pushes in from the west.

Light snow will overspread the area from west to east on
Sunday, accompanied by reductions to MVFR/IFR conditions. This
will occur between 14Z and 18Z in the western and central
airfields, and between 20Z and 22Z in the southeastern
airfields. Snow should be ending at all airfields between 01Z
and 03Z Monday. After that, expect conditions to return to MVFR
and gradually increase to VFR, roughly by daybreak on Monday.

Outlook...

Mon...VFR early, with light snow and restrictions developing
across the N/W late.

Mon night-Wed...Restrictions likely in light snow/snow showers,
especially N/W.

Thu...Generally VFR.

&&

.CLIMATE...
A new record low of -18F was set at Bradford (Airport) this
morning. This broke the old record of -14F set in 1984.

As a reference, this is not close to the
PA state record of -42F set in Smethport (not far away) in
January (5th) of 1904.

&&

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

&&

$$
SYNOPSIS...Lambert/DeVoir/Dangelo
NEAR TERM...DeVoir/Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Evanego/Banghoff
AVIATION...Evanego/Gutierrez
CLIMATE...