780
FXUS61 KCTP 221945
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
245 PM EST Fri Nov 22 2024

.SYNOPSIS...
* Snow shifts into the Laurel Highlands this evening; otherwise
  cloudy and breezy with a spotty rain or snow shower tonight
* Breezy with showers over the western Alleghenies to start the
  weekend, followed by improving conditions on Sunday
* Windy with rain and snow showers Monday night into Tuesday;
  another potential bout of winter weather possible for
  Thanksgiving Day

&&

.NEAR TERM /THROUGH TONIGHT/...
18-20Z radar trends show precip band weakening over northeast
PA across the western Poconos and Endless Mountains. Warmer air
wrapping around trowal feature associated with stacked deep low
is advecting warmer air into the region from the north - which
ia bit unusual but to be expected in this pattern. Steady to
slowly rising sfc temps expected through tonight favors a
transition to rain/snow mix or plain rain ptype in most
locations. The highest terrain >2500ft in the Laurel Highlands
should keep snow ptype the longest, with peak snow rates of 1-2
in/hr expected through at least 23Z/6PM coinciding with the
strongest WNW upslope flow 45-50kt. We added near blizzard
conditions into the WSW which remains in effect until 12Z
Saturday; however there are some indications that this timing may
be a bit long in the tooth given increasingly marginal sfc
temps reducing snow accumulation. All other winter headlines set
to expire on time at 21Z/4PM. Cloudy and breezy conditions
expected elsewhere overnight with a fairly tight minimum temp
spread in the low-mid 30s.

&&

.SHORT TERM /SATURDAY/...
WNW flow on the backside of departing upper low will allow rain
and snow showers to linger for the start of the weekend downwind
of Lake Erie and over the Allegheny Plateau. Gusty winds 25-35
mph continue adding a wind chill to an otherwise mostly cloudy
and raw late November day in central PA. Max temps will be near
to ~5F below the historical average (it`s been a while) with
highs 40-50F - but it will feel more like 35-45F when factoring
in the brisk WNW wind.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
* Winter Weather may impact travel on Thanksgiving Day across
  Central PA

Sct-nmrs SHSN linger over the Alleghenies Sat night with only
minor addtnl accums. Then the temp advection turns positive on
Sunday and should lift any remaining SHSN up into NY. High
pressure doesn`t last long with a progressive storm affecting
the state late mon into Tues morning. Milder conditions (+5F vs
Sun) look likely for Monday in advance of the storm. Temps
should stay mild enough to be only rain for all of the area.
Latest guidance supports minT in the 40s area-wide Mon night.
CFROPA in the late night/early morning time-frame will probably
keep the chc for thunder low, but would not be surprised to hear
a rumble or two since the front is potent and 8H temps drop 15C
over 12 hrs at UNV. Could be a gusty passage, too (potential
NCFRB) due to 8H winds from 240deg at >=50kt per GFS. Tues looks
mainly dry under high pressure. Perhaps a SHSN NW.

Wed now looks fairly good for travel across PA with most models
converging on a Thursday/Thanksgiving Day arrival for the next
precip event. However, they are not in lock-step. Cold llvl air
residing north of the Mason/Dixon line combined with a zonal
WSW jet aloft across the ern 2/3rds of the CONUS will likely
lead to a fast, progressive flow.

The front that pushes S of the commonwealth Tues will stretch
out West to East to the south of our latitude, and moisture
should start to return and pool up along it on return flow from
the GOMEX. How far south will it be on Thursday is the tricky
part to the forecast. 00Z ECMWF generates a widespread QPF of
0.5" across most of the CWA. 12Z operational GFS has the sfc
ridge stronger and farther south on Wed. The result is that it
would take most of the precip from a much weaker and quicker
wave to the south of PA. Thus, the confidence level has not
increased all that much over the past 24hrs. Continuing with
PoPs maxed at about 70pct on Thanksgiving Day.

That said...The thermal profile for the start of any precip
late Wed or Thurs would likely be cold enough over some (nrn)
portion of the CWA to make frozen or freezing precip. Temps in
the lower elevations may be warm enough for only rain there.
But, arrival timing (before/after sunrise) and depth of cold air
in llvls will have a big influence on p-types. At this point,
the prudent answer to the question about Thanksgiving`s weather
reads:
"The probability for measurable snow is highest in the northern
tier and lowest in the lower elevations of the southern tier.
There is also a non-zero chance of freezing rain across Central
PA, but something less than 20pct at this point. Continue to
monitor the forecast as confidence is expected to increase over
the next 2 to 3 days. Be prepared for slippery/poor travel
during this upcoming long holiday travel time."

Current timing and placement of mass features should allow for
gusty winds and drying on Friday except in the northern
Alleghenies where the cold air and WNW flow will generate
lake effect SHSN which may linger thru much of next weekend
(days 7-9). A shot of even colder air comes along late in the
weekend, and looks like a pattern favorable for snow squalls.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Conditions (mainly low cigs) will slowly improve from IFR
toward MVFR/low VFR at terminals to the east of the Allegheny
Plateau tonight with rain/snow ending. KJST will continue to
hold at or below airfield minimums with moderate to heavy snow
through at least 06Z followed by marginal/gradual improvement
into Saturday. Gusty winds 20-30kt from 280-320 degrees will
continue through Saturday.

Outlook...

Sun...MVFR cigs NW 1/2 impacting KBFD and KJST. VFR elsewhere.

Mon-Tue...Strong CFROPA Monday night with rain and potential
LLWS followed by strong winds and snow showers.

Wed...Not as windy with MVFR to VFR cigs; mixed precip could
reach the southwest airspace by 12Z Thu.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 4 PM EST this afternoon for
PAZ004-005-010>012-017>019-025-034-045-046-049-051-052.
Winter Storm Warning until 4 PM EST this afternoon for PAZ006-
037-041-042-053-058.
Winter Storm Warning until 7 AM EST Saturday for PAZ024-033.

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Lambert/Dangelo
AVIATION...Steinbugl