334
FXUS61 KCTP 301909
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
309 PM EDT Tue Sep 30 2025

.SYNOPSIS...
* Very warm last day of September followed by a brief cool down
  to start October
* Potential frost and freeze conditions, mainly across the
  Northern Mountains, Wednesday night and early Thursday
  morning
* Our building string of dry days will likely extend for another
  week to 10 days as temperatures moderate into next week

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The shield of mid and high clouds associated with Hurricane
Imelda continues to erode away/drift south this afternoon, with
roughly the northern two thirds of the Commonwealth now cloud-
free as of mid afternoon Wednesday. High temps in the mid 70s
across the higher terrain of the north and west and in the upper
70s to low 80s in the Central and Southern Valleys is several
degrees above average for this time of year.

A dry/backdoor cold front will drift south through Pennsylvania
this afternoon and overnight, ushering in seasonably cooler and
drier air on a steady, 5-10kt breeze from the N/NE. This cold
front will be pushed along by a strong surface high, ensuring
cloud-free skies overnight. Lower dewpoints will filter in
overnight, dropping into the mid 30s to mid 40s by daybreak
Wednesday. Winds will stay sufficiently breezy overnight to
preclude any frost concerns, but low temperatures could dip
into the mid to upper 30s in the typical cool spots of northern
PA. For most, though, temperatures will be in the mid 40s to low
50s on Wednesday morning. The northeast winds will also prevent
any fog concerns tonight.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
October will start with seasonably strong 1032+mb Canadian HP
drifting southeast from Hudson/James Bay into northern New
England. The cooler and drier low level flow from the N/NE will
bring a noticeable cool down for Wednesday and Thursday. Afternoon
highs on Wednesday will turn out to be 5-10 degrees lower vs.
Tuesday...in the low 60s/70s. Thursday looks cooler yet as
southeast flow rotating around the sprawling high will set up a
typical cool-air damming scenario. Highs likely struggle to
crest the 70F mark on Thursday.

Clear skies are a sure bet for Wednesday night with high
confidence for frost/freeze over northern PA, given diminishing
wind, low dewpoints and min temps in the low to mid 30s. GFS MOS
guidance shows 33F for Bradford at sunrise Thursday, which
highlights the fact that and anomalously dry airmass underneath
high pressure this time of year can yield under-performing
temperatures.

The chance for freezing temperatures remains low enough that a
Freeze Watch is not needed, but a few spots below 32F cannot be
ruled out Thursday morning. That being said, frost is nearly a
sure bet for a stripe of counties along the PA/NY border with
potential all the way down to I-80. Folks with active
gardens/flowers should prepare to take necessary steps to
protect vulnerable vegetation.

Clouds will be on the increase a bit Thursday night, which
should keep temperatures above the frost/freeze mark by Friday
morning.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Slow moving and blocky pattern under deep layer ridging over
the Mid Atlantic and Northeast states will lock-in the renewed
run of dry wx through the first weekend of October. NBM/WPC QPF
is 0.00" in CPA for the next 7+ days.

As high pressure moves just each of the region later this week,
southwest flow will usher in slightly milder temperatures each
day. Temperatures moderate back to well-above normal by the
second half of the weekend. Calm winds combined with clear skies
and a gradual uptick in surface moisture will likely lead to
daily occurrences of fog in the typical river valleys across
northern PA. The return of the multi- day/persistent parched
pattern could offset any short term improvement in the low-end
drought conditions from much needed/beneficial rainfall last
week.

There remains considerable spread in long-range guidance
regarding the potential for some rain by the middle of next
week. Even if a weather system moves through, rainfall totals
will likely be minuscule because there is no tropical moisture
in sight in the Mid-Atlantic.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Widespread VFR flying tonight through midweek. Gradient wind
from the north/northeast (360-060 degrees) will preclude fog
formation overnight and increase by Wednesday afternoon with
gusts up to 20kts possible across the northeastern 1/3 of the
airspace.

Outlook...

Thu-Sun: AM fog; otherwise VFR.

&&

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

&&

$$

SYNOPSIS...Banghoff/Bringhurst
NEAR TERM...Banghoff/Bringhurst
SHORT TERM...Banghoff
LONG TERM...Steinbugl/Banghoff
AVIATION...Steinbugl