135
FXUS61 KCTP 060220
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1020 PM EDT Sun Oct 5 2025

.SYNOPSIS...
* Dry conditions with well above normal daytime temperatures
  will continue on Monday under the influence of high pressure
  centered off the Delmarva Coast.
* Increased rain chances Tuesday through Wednesday morning with
  an approaching cold front.
* Dry and notably cooler conditions return for the second half
  of the week with overnight low temperatures pushing closer to
  the freezing mark.

&&

.NEAR TERM /THROUGH MONDAY/...
Patchy Valley fog and some small areas of low clouds in the
Lower Susq Valley is the only forecast concern for later
tonight/early Monday. Even with respect to fog, forecast min
temps will create an air/water temp diff of less than 15 deg F,
which greatly minimizes the extent of fog in the larger stream
and river valleys.

Temps are going to be a deg or two milder tonight vs last
night, the wind will be calm again and dewpoints may be a few
deg F higher. Rule of thumb that says "If your temp reaches the
aftn dewpoint overnight, you`ll fog in" and is valid tonight.

That seems to fit over the SE half of the area. But, it probably
won`t be a solid/wide patch of fog/low clouds. Will call it
patchy fog for the time being and let the overnight shift
refine that IF NEEDED. Otherwise, temps dip into the m40s-m50s.

&&

.SHORT TERM /MONDAY NIGHT THROUGH 6 PM MONDAY/...
Still looks great (dry and warmer than normal) Monday after any
patchy morning fog burns away. Wind should pick up a little,
and mainly from the S/SW. But, the wide gradient will mean the
direction may be just as dependent on local effects than the
gradient. The hill-top sites (BFD/JST) should be a little better
bet to follow the gradient-based guidance. A bit more moisture
starts to stream in from the west aloft. So, not another sunny
day, rather mostly sunny with just mid-high clouds in the warm
sector.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
The aforementioned (short-term) surface low pressure system
continues to shift northeastward into northern Ontario/Quebec in
the beginning stages of the long-term forecast period. This
track allows for a cold frontal passage to occur across central
Pennsylvania Tuesday into Wednesday morning. Rain chances start
to increase Tuesday late morning/early afternoon generally in a
northwest-to-southeast across the forecast area with the bulk of
precipitation expected to occur through Wednesday afternoon
based on recent GEFS plumes. There remains some model disparity
in timing; however, with the best chances of precipitation
across the northwestern half of the CWA mainly in the Tuesday
afternoon/evening timeframe. QPF returns continue to look
overall unimpressive in terms of a "drought-busting" with
current QPF form this system generally under one inch across the
entire forecast area, in fair agreement with recent
deterministic model guidance, outside of the ECMWF that does
outlines spot amounts just above one inch. At this time, have
leaned towards the GFS solution, as instability remains to
appear weak, thus general thought is that it will be harder to
come by those spot amounts reaching over one inch.

Dry conditions (once again) seem to be in play as the cold
front clears the region by Wednesday afternoon/evening as high
pressure builds into the region. Recent model guidance shows
fair agreement with regards to the aforementioned 1032mb high
pressure setting up directly over the region, allowing for clear
skies and ample radiational cooling across central Pennsylvania
Wednesday night and Thursday night. Freeze concerns are
becoming increasing likely across the northern tier of
Pennsylvania on Wednesday night, with recent NBM guidance
outlining near-to-sub 32 degree temperatures across portions of
McKean and Potter Counties for multiple cycles. Frost concerns
appear increasingly likely for the bulk of the area Wednesday
and Thursday nights outside of the south-central and Lower
Susquehanna Valley zones; however, less confidence on the
southeastward extent at this time.

Fair amount of uncertainty resolves towards the end of the
long-term forecast period with recent deterministic model
guidance outlining two separate solutions for the Friday and
Saturday forecast periods. Main source of uncertainty comes with
respect to the upper-level pattern. First solution outlines an
amplified trough at 500mb bringing some rain chances to central
Pennsylvania later on in the afternoon/evening Friday and into
Saturday morning. While the second solution outlines a slightly
less amplified upper-level trough potentially leading to less
rainfall chances. Given the spread in model guidance, have
decided to roll with NBM this cycle.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
Another really nice afternoon, evening outside for early Oct.
Not much change to the TAFS for the 00Z package, from the 18Z
TAF set. Overall not much fog last night, expect conditions to
be similar tonight. The pressure gradient might support a little
less chance of fog than last night, but then again we did not
get much fog last night. For now went close to what the day
shift had.

Earlier discussion below.

Worries/challenges for fog resume later tonight, but more so
over the SErn two airfields (MDT/LNS). The temps should drop
down to the dewpoints from this aftn and meet up with the temps
there. That is a good sign for fog to develop. However, the
more-susceptible places are the valleys where the temps should
get very slightly cooler overnight. At this point, fog will be
mentioned at BFD, IPT, MDT & LNS. BFD mainly because of them
cooling into the m40s. IPT because of their proximity to the
river. Have serious doubts about both those locations fogging
in, though. MDT and LNS seem to be the best bets to fog in. AOO
and UNV could also get some brief fog, but confidence is low
there. Some guidance (mainly the NAM) has a low deck forming in
the SE, too. But, we`ll stay away from that as HREF probs are
<20pct of <1SM BR there. SREF probs are higher (still <30pct)
over MDT/LNS and IPT.

After any fog/low clouds burn away between 12 and 14Z, some
mid-high clouds do start to move into PA from the W. However,
it should still be VFR into late Mon night. The clouds will
stay generally N/W of the Lower Susq, so fog/low clouds could
form again Mon night there. HREF probs of ceiling <1000ft are
30-40pct by 12Z Tues. The front and a upper shortwave trough
approach later Mon night. SHRA are possible toward dawn Tues AM
in BFD, but wait until late Tues for the SE.

Outlook...

Tue...Sct SHRA. TSRA poss W & S late.

Tue PM...CFROPA. SHRA/TSRA. IFR fog poss mainly NW.

Wed...Sct AM SHRA SE. Otherwise becoming VFR.

Thu...AM fog then VFR.

Fri...AM fog, otherwise clear with VFR conditions.

&&

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

&&

$$

SYNOPSIS...Lambert/Dangelo
NEAR TERM...Lambert/Dangelo
SHORT TERM...Lambert/Dangelo
LONG TERM...NPB
AVIATION...Dangelo/Martin