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509
FXUS61 KCTP 251247
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
747 AM EST Sat Jan 25 2025

.SYNOPSIS...
* Temperatures will continue to trend up through the weekend
  with highs back to near- normal by Tuesday (upper 20s to low
  40s).
* Moisture challenged system in the form of a warm front and
  very weak cold front moves across the state today and early
  Sunday respectively to bring a coating to a few inches of of
  snow to the Northwest Mountains and Laurel Highlands by Sunday
  afternoon.
* Blustery conditions return for the early to middle part of
  next week with periods of snow Tuesday and Wednesday and wind
  gusts from the west-southwest exceeding 40 mph on Wednesday,
  especially north of I-80 and west of I-99.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
Nighttime Microphysics Sat imagery shows mainly clear skies
holding on across the eastern half of PA, while a shield of
thick mid level clouds was spreading across the Western half of
the state in advance of a warm front.

Temps across the bulk of the CWA were in the single digits above
zero to around 10F in some spots across the west.

Latest high res model guidance indicates that by noon (and
afternoon a few to several hours of morning sunshine across the
eastern half of PA), practically the entire CWA will be covered
by a dual to multi-layer of clouds that will persist into
tonight and likely Sunday too.

Any light snow from the aforementioned thickening cloud cover
will be limited to the western mtns (particularly the NW Mtns)
from the Mid afternoon on where a layer of lower cloud cover
will support the snowflakes growing within the mid cloud layer
where the thermal ribbon for Dendritic Growth will be centered.
Elsewhere, too much llvl dry air will preclude anything more
than a few snowflakes reaching the sfc, but we should see some
decent virga.

High temps today will vary from the mid to upper 20s across the
Mtns to the low 30s across the valleys of Central and Southern
PA.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...
Forecast for the moisture challenged system to impact NW/NC PA
late today into Sunday is still on track with no sig changes in
this early Sat update.

A period of warm air advection in association with a warm front
extending out ahead of the next northern stream system will be
followed by another moisture starved/weak cold front that will
cross the region tonight and early Sunday.

Weak low-mid level CAA in its wake will help to generate
another period of lake effect and upslope snow showers over
Laurel Highlands NW Mountains.

Northwest PA will be see the best chance for 2 or 3 inches of
snow as they will be under the right entrance region of a
110kt 200 mb jet overhead tonight.

A few spots may could exceed the 3" mark if aforementioned jet
dynamics can overcome the dry boundary layer.

Scattered snow showers/flurries will linger on Sunday across the
Northwest Mountains and Laurel Highlands regions with
additional accumulations generally remaining below 1 inch.

Persistent southwest flow will and building upper level ridging
into Sunday afternoon will support a continued warming trend.
High temps Sunday afternoon will approach 40 degrees in the
southeast.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
A deepening low over northern Canada and building high pressure
over the Central US will generate a tightening pressure
gradient and gusty winds in Pennsylvania by Monday afternoon.
With highs forecast in the upper 30s for much of southeast PA
along with mostly sunny skies, the gusty winds should help erode
away some of the existing snow. Farther northwest, temperatures
will be within a few degrees of the freezing mark.

Medium range guidance supports mainly dry and seasonably cold
weather early next week, as upper level troughing remains over
the region. One notable shortwave is progged to drop south
across the region later in the day on Tuesday, with will
reinforce colder air across the region. An uptick in moisture is
expected, outlined in recent PWAT anomalies, suggesting a round
of snow showers along the associated cold front Tuesday with the
best chances across our northern/western zones. Guidance does
continue to indicate marginal instability across the northern
tier of counties, indicating some snow squall potential later in
the day/early Wednesday morning.

With regards to lake effect snow in the upcoming week, northwest
flow behind the front is likely to produce lake effect snow
showers into Wednesday. Ice cover across Lake Erie will dampen
this potential, with any accumulation across NW PA expected to
be minimal. A second shortwave may also track north of PA on
Wednesday, which will support chances on Wednesday, with lake
effect showers later in the day and into Thursday in the wake of
this shortwave. There still remains some uncertainty on
shortwave progression in this timeframe; however, so have stuck
closer to NBM PoPs in this timeframe.

Given the uncertainty in shortwave progression, this will also
bring about some uncertainty with the temperature forecast in
this timeframe with a wide spread in recent ensemble plumes. The
remaining uncertainty has led towards sticking close to the
most recent NBM into the latter part of the week, as well.

There is a signal for potentially unsettled conditions late next
week, and with a wide spread in aforementioned T profiles, ptype
will be challenging as well. But the general idea of a snow to
mix seems reasonable should the system come to fruition late
Friday and extending into next weekend.

&&

.AVIATION /13Z SATURDAY THROUGH WEDNESDAY/...
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A weak area of low pressure tracking across the N Grt Lks will
first spread increasing mid level clouds, which will lower to
a thick strato cu layer later this afternoon and tonight across
much of the region with generally MVFR conditions from late
evening on (outside of the Lower Susq airfields KMDT and KLNS
where OVC VFR CIGS will be found).

Light snow likely this afternoon/evening over the NW Mtns, and
then gradually spreading SE toward KFIG, KDUJ and KJST late
today and this evening.

Model soundings and ensemble prob charts indicate that
borderline IFR conditions will become possible by early this
evening, roughly north of KFIG.

Increasing west-southwest winds aloft, combined with light
surface winds will lead to LLWS across the board tonight/early
Sunday.

Outlook...

Sun...AM low cigs/light snow possible W Mtns. Early AM LLWS
possible. Westerly wind gusts 25-30kts beginning Sun morning in
the west and likely overspreading the rest of the airfields
Sunday afternoon.

Mon...Gusty southwest winds. Light snow possible by evening NW
Mtns.

Tue...Gusty northwest winds. Evening light snow possible N Mtns.

Wed...Early AM light snow possible N Mtns. PM snow squalls
possible W Mtns. WSW wind gusts in excess of 35 KTS possible
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...Lambert/DeVoir
NEAR TERM...Lambert/DeVoir
SHORT TERM...Lambert/DeVoir
LONG TERM...DeVoir/Fitzgerald/NPB
AVIATION...Lambert/Fitzgerald/Gartner