124
FXUS61 KCTP 100059
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
759 PM EST Sun Nov 9 2025

.SYNOPSIS...
* Low pressure overhead will slide east this evening and wrap
  cold air into PA tonight, with precipitation gradually
  changing over to snow showers across the northern and western
  highlands.
* Lake-effect and upslope snow showers continue Mon into Tues,
  along with the coldest temperatures of the season thus far.
* Temperatures should begin to moderate by late week.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Quite a complicated sfc map early this evening for the Mid
Atlantic/Lower Glakes region as at least 4, distinct approx 1005
mb sfc lows extend from near KBGM, south to KDCA and just SE of
KISP.

A narrow wedge of weak sfc-based CAPE (associated with TDs in
the mid to upper 50s F) nosed into far SE PA (to near KLNS)
where residents to the south likely heard some rumbles of
thunder from the northern edge of a line of storms that
recently rolled across far southern Lancaster County. Lower
dewpoint air will push into the Susq Valley overnight in the
wake of the Lee Trough, and later on across the entire CWA
after the passage of a southward mvg cold front as the several
aforementioned sfc lows consolidate near KLGA as the larger
scale uvvel associated with a 130+ KT upper level jet across the
Alleghenies of PA/WVA shifts east to the Mid Atl Coast.

Previous Disc with some augmented/updated details...

The air temps in swrn NY are already down into the 30-32F range
with the SFC cold front (trailing WSW from one sfc low near
KBGM) pushing south to near I-80 in wrn PA at 0030Z Mon.

Thus, the expected turn to snow showers from rain showers looks
on track for sometime through this evening across the far NW
and around midnight over the Laurels.

No significant snowfall is expected overnight. Some melting may
take place at first as the ground (esp the roads) are warm.
However, air temps dip to the 20s around midnight in Warren Co.
That could make already- wet roads icy, if not treated, tonight.
Accums could be 1-2" for Warren and western McKean Co overnight
and less than an inch along the rest of the western highlands.

A relative min in precip will occur between the I-99 corridor
and RT 15 in the Lower and Middle Susq Valley.

The valleys will stay milder, and most places SE of a AOO-UNV-
IPT line will likely not hit freezing before sunrise. But, the
higher elevations in the central mtns probably will. So, there
could be a dusting there above ~1700ft. The flow around the
departing low will kick up with gusts into the 20s, bringing
wind chills into the teens in the NW and 20s elsewhere.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
The cloud-layer flow moving across the lakes on Monday will be
light and directionally-sheared at first, then settle into a
more-stacked NW direction. Lake induced CAPE (51F lake water at
ERI) could reach into the 1000J range with clouds tops in the
5-10kft range. However, the cross-fetch is short at that angle
and would likely keep all but NWrn Warren Co from getting much
accum, esp as temps get close to freezing (and the sun makes
the ground/sfc slightly warmer). However, it`s still wise to
keep a half inch or so in for the NW mtns with this flow. The
rest of the Alleghenies and Laurels will lack snow on the whole
as clouds lose their moisture moving too far away from the lake,
and the deeper plume of moisture from OH (what used to be
connected to/from LM) slide south into WV. That should keep even
the Laurels mainly dry (just a dusting) thru the daylight hrs.

As the sun lowers, the flow will back to west a little and get
an significant addition of LH moisture. This two-lake fetch and
a llJet of 40-45KT will be pointed right into Warren/McKean Cos
for much of Mon night (and into Tues). The SLRs thru the period
will lower to about 17:1 in the nrn mtns. So, it`s not out of
the question for the healthy band/bands to drop >6" in Warren Co
as the moisture rolls uphill. Not so sure about McKean and
Potter Cos, as they are farther from the lakes and the moisture
might not last that long/far into the CWA. At the same time, the
upslope flow into the highest hills of Somerset CO (and all of
PA, really) moistens up again as the flow backs there, too, and
brings the best moisture back N from WV/MD. The residence time
of the (combined) best moisture and uplift over the Laurels
looks short, though. Thus, additional snowfall Mon night and
early Tues is very much in question. Also, the lower 2/3rds
(elevation-wise) of the county will likely get (way) less than
3" for the whole stretch. So, we`ll hold off on any WWA flags
(advy) for Somerset Co at this point in time. We`d like to see
another cycle or two of guidance for that area. A watch has been
posted for Warren Co, and McKean Co (maybe Potter/Elk) might
also need an advy for late Mon into Tues. But, certainty in 3+"
accums are much lower there than in Warren Co. Will hold off on
that, too.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Upper-level troughing will remain in place through the end of
the week, keeping the chance for rain and snow showers in the
forecast each day through Friday, especially over northwest PA.
A tight pressure gradient will allow for winds gusts in the 30
to 35 mph range Wednesday, with some guidance suggesting the
potential for gusts over the Laurel Highlands to approach 40 to
45 mph.

The December- like cold airmass is forecast to retreat later in
the week, with temperatures returning closer to seasonal
averages. High pressure attempts to briefly build in from the
west which should keep us mainly dry into the beginning of the
weekend, but uncertainty increases by Sunday regarding the
timing of an approaching frontal system.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
A big dry slot/occlusion is moving thru the CWA at 19Z. The sun
will raise CAPE and convective depth of the clouds moving
quickly in from the west (over JST now). That convection will be
capable of making TSRA, but mainly isold, and the better chance
for that is over IPT, and MDT/LNS (where they already had an
isold TSRA nearby earlier this morning). Will not go too
heavy/long with TSRA mentions, rather confining the mentions to
the couple of hrs most likely per HRRR guidance (generally
21-01Z).

As the bigger shield of rain/showers over the N has already
gone, and the big patch of RA over CLE is right under the best
vort max. Therefore, we do expect rain to move in from the west
again late this aftn and evening. As it gets colder (JHW down
into the 30s already) on the N/NW flow across the lakes from
Canada, we`ll see the p-type turn to SN over the west (BFD first
around 02Z and JST a little later, like 05Z). The flow will
keep low clouds a certainty for the NW half to two-thirds of
the CWA. Lake effect clouds and precip will keep things IFR in
the NW and MVFR to lower VFR for the middle 3 terminals (AOO-
UNV- IPT). But, little to no vsby restrictions will be had for
anyone but BFD and JST. It`s always tough to remember just how
fast the vsby comes down when snow is falling. It`s tough not to
be IFR if there is snow falling. Quite a difference from summer
when it`s tough to be IFR unless thunder occurs with rain (or
foggy/low clouds are there, too).

The lake effect and upslope snows will continue into Tues.
There are a couple periods that should be quieter (less
snow/reduced flight conditions) as a good plume of moisture
that points at the Laurels Sun night and early Mon morning
slides decidedly to the S of PA. Thus, the daylight hours on Mon
will be least likely to have snow falling.

Outlook...

Wed-Thur...Slightly milder, but blustery with MVFR/IFR
conditions in lake effect/upslope snow (rain mid-day) at
KBFD/KJST. MVFR to low VFR cigs elsewhere. Sfc wind gusts
20-30kts from 260-290 degrees (mainly during the day).

Fri...Better. SLGT CHC SHRA N. Otherwise VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from Monday evening through Tuesday
afternoon for PAZ004.

&&

$$

SYNOPSIS...Lambert/Dangelo/Evanego
NEAR TERM...Lambert/Dangelo
SHORT TERM...Lambert/Dangelo
LONG TERM...Bauco
AVIATION...Dangelo/Gartner