848
FXUS61 KCTP 010732
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
332 AM EDT Mon Sep 1 2025

.SYNOPSIS...
* Dry weather is expected to continue through the middle of this
  week, featuring cool nights, and warm comfortable afternoons
* Aurora Borealis may be visible Monday night; Geomagnetic
  Storm Watch in effect
* Next widespread chance for rain comes Thursday with a cold
  front. Scattered showers possible Wed in western PA

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
CLouds creeping in from the east are not just cirrus, but also a
broken low/mid deck. That increase in moisture aloft looks like
it will slide steadily to the west as the sfc high pressure to
our north slides to the east. The clouds will be around all day
and over much of the CWA, but should not be a solid deck
everywhere. Many holes will be found. Very patchy fog is
forming over the N/W, and should dissipate as normal 1-2hrs
after sunrise. The dry airmass in the lowest 5-7kft will make it
very difficult for any precip trying to drop out of the clouds
to reach the ground. So, while some models are generating spotty
0.01" across the CWA, we`ll leave the forecast dry. Maxes today
are expected to be 1-3F warmer in the NW, but near where they
were Sunday everywhere else.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...
Valley fog is not as likely tonight as in many previous
mornings, mainly due to the expected presence of a scattered to
broken sky cover. While fair wx clouds are not usually a cause
for special attention in the forecast, there is the possibility
for northern PA to see Northern Lights tonight. Other aspects
of the forecast (wind, temps, dewpoints, etc.) are well in hand.
But, the cloud cover will be a difficult call. The GFS and NAM
mid-level RH progs yield a high confidence in clouds hanging on
or even developing through the night (and lasting into
Tuesday). For now, to reflect expected breaks in the clouds, we
have generally 30-50pct coverage over all of the CWA through
most of the night. This coverage percentage may need to be
bumped up in later updates.

The mins tonight will be trending up from Monday morning`s
lows, esp in the NW. While BFD and other cool spots on the
Allegheny Plateau may dip into the 40s, all others should stay
above 50F. Maxes Tuesday will be nearly the same as Monday. The
wind will be veering to a more-southerly flow at the sfc, but
the expected bkn clouds will dim the solar heating a bit. There
is an outside (10%) chance for some of the clouds to get thick
enough to rain, but the dewpoints will still be fairly low/dry,
and the precip would have a tough time making it all the way to
the sfc.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
3 AM Update...
Dewpoints on Wed do not look as low as they did for the last
forecast cycle. The resulting MinRH numbers are (well) above
red flag threshold, and wind generally below threshold.
Confidence continues to increase in the PoPs (SHRA/TSRA) on
Thursday and early Thursday night. However, we`ve had a dry
spell lately. The old adage "drought begets drought" holds
merit. It might be a little more difficult to generate
widespread showers without ground moisture to help the advected
moisture (moisture brought in from elsewhere) grow the clouds.
At this point, the highest PoPs are centered on the proper time
(thursday and the first half of Thursday night). Will everyone
in Central PA get wet? Probably not. But, the NW is most-likely
(80-90%) to get wet, while those south of the Turnpike are least
likely (60%) to get wet.

Prev...
The upper-level, synoptic-scale configuration looks to feature
a transition towards an amplified pattern, with a building
western North American ridge axis, a deepening Great Lakes and
Midwestern trough axis, and a western Atlantic ridge for the
long term period. Given consistency of our ensemble prediction
systems in showing this pattern, confidence is relatively high.

At the beginning of the period, with a deep layer of dry air
still in place and continued moderation of daytime highs over
time, minimum afternoon RH values will dip. Gusty southwest
winds ahead of an approaching cold front on Wednesday could also
lead to an enhanced risk of fire weather concerns.

Later in the week, it is anticipated that the lower-level flow
will turn more southerly and bring increased moisture into the
region. Also, with an approaching cold front from the northwest
and deepening troughing aloft upstream (mentioned above), the
chances for showers should increase. Latest WPC QPF for Thursday
paints a fairly widespread 0.50" area across Central PA, which
would be welcome after a prolonged dry stretch. Unless there is
a well- organized or tropical system, QPF tends to decrease at
shorter lead times (drought begets drought is what we say a lot
around here), but time will tell with this one.

Friday should feature variable amounts of clouds with a
moderately gusty SW breeze, generally dry conditions and max
temps coming in a few to several deg below normal (Upper 60s to
around 70 across the Northern Mtns and Upper 70s in the Southern
Valleys).

A compact shortwave and weak low pressure tracking east across
the Lower Great Lakes will be followed by second push of cooler
air for Friday night into next weekend. The timing of the Cfropa
has 12+ hours of spread between the similar GFS and ICON models
vs the EC (which is the slower solution not pushing the front
through until the daylight hours on Saturday and
preceded/accompanied by a few areas of showers).

The NBM seems to be weighted more toward the slower solution,
but with more diffuse upper dynamics and meager sfc moisture
convergence, yielding only about 20 percent pops for showers on
Saturday.

In the wake of the cold front next weekend, lake effect rain
showers are expected across northwest PA as cold advection
resumes. Latest ensembles indicate another stretch of below
normal temperatures and frost potential across the typical deep
/ protected valleys of northern and central PA.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
VFR conditions and light winds will prevail across the region
overnight and into Monday, as surface high pressure remains in
control. Potential for fog tonight is lower than previous
nights, but some patchy valley fog is still expected mainly in
the deeper river valleys of the northwest. Brief restrictions
possible at BFD, but probs too low for mentioning in the TAF.

Scattered to broken stratocu is expected to develop between 6000
and 8000 feet across east central PA this morning and expand
westward through the day as easterly flow brings in some
moisture from the ocean.

The next chance for numerous SHRA and TSRA is on Thursday with
the arrival of a cold front.

Outlook...

Tue...AM valley fog possible; otherwise predominantly VFR.

Wed...Mainly VFR. Isolated SHRA possible in the late afternoon
mainly south and west of JST.

Thu...Widespread SHRA expected with TSRA possible.

Fri...Showers lingering, mainly across the east.

&&

.CLIMATE...
A record low temperature of 39 degrees was set at Altoona
yesterday, Aug 31. This breaks the old record of 40 degrees set
in 1986.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Lambert/Dangelo/Banghoff
AVIATION...Colbert
CLIMATE...Colbert