Oregon, Pennsylvania Weather Forecast Discussion

511
FXUS61 KCTP 042131
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
531 PM EDT Sat Oct 4 2025
.SYNOPSIS...
* Dry, pleasant early Autumn weather continue over this weekend
  and into early next week with well-above normal temperatures.
* A cold front will push east across Pennsylvania late Tuesday
  into Wednesday morning bringing a few periods of showers.
* Dry and cooler conditions return for the second half of next
  week with overnight low temperatures approaching the freezing
  mark in the northern tier and colder valleys of central PA.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Dewpoints a few degs higher than fcst right now, but we are
getting a little deeper mixed layer, seeing cu over South
Mountain. Thus, they could drop rather quickly for late aftn.
Otherwise, the main challenge tonight is just how much fog will
form. Dewpoints will be higher by a little vs Sat AM, but so
will be the temps. It won`t hurt to add a little fog in for the
valleys of the N and Confluence since they have been fogging up
the past few nights. Center of the sfc high slides east a little
more overnight. Mins of 45-55F with 50F being most the common
number.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
Sfc high will continue to slide east a few furlongs and the sfc
wind flow will be a little more consistently S during the
daylight. Any morning fog will burn off even quicker than Sat
AM. The upper ridge axis will be centered overhead on Sun,
allowing for very little cirrus. The NAM mixed layer is very
shallow right now and may be too shallow again Sun, so that
explains the very much lower MOS guidance on MaxT vs the GFS/MAV
guidance. The current GFS is closer to the current RAP mixed
depth, so it may be handling the mixing better today/Sat. We are
expecting that more-consistent S wind, too. So, we will be
following mid-pack NBM maxes plus 1F.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
The dry and warm pattern Sunday night through Monday night will
give way to the next opportunity for rain by Tue-Wed as surface
low pressure from the central US tracks northeastward into
Ontario. The low will drag a cold front through the area,
bringing some rainfall to central Pennsylvania.
While there should be decent moisture return ahead of the front,
with PWAT values rising to the 1.25-1.4 inch range (~90th
percentile for this time of year), there is still some
uncertainty as to just how much rain will fall. Ensemble mean
QPF is generally around 0.50-0.70 inches in northwest PA, with
lesser amounts as you move south and east, but some of the
deterministic guidance, namely the past few runs of the GFS,
continue to show the potential for over an inch of rain over
parts of central PA. This does not appear to be the most likely
solution at this point, however, as most guidance shows the best
synoptic scale forcing passing well to our north and more
detached from the tropical moisture stream. Additionally, weak
instability should help to limit rainfall rates.
All guidance shows high pressure building into the region at the
surface and aloft in the wake of the cold front. This setup
would allow for another spell of dry weather into the latter
half of the week. With a 1030 mb surface high expected to be
centered over the region Wednesday and Thursday nights, ideal
radiational cooling conditions are anticipated with mainly
clear skies and light winds. Temperatures will fall into the 30s
and 40s both nights and frost formation is likely over the
north and west. There is also some potential for temperatures to
drop below freezing Wednesday night across the northern tier and
colder valleys of central PA. Daytime high temperatures will be
5 to 10 degrees below normal, ranging from the upper 50s to the
mid 60s.
Temperatures will return closer to normal for the end of the
week and into the weekend as the surface high moves off to the
east and southerly flow develops. There is quite a bit of spread
in the guidance regarding the upper level pattern as we head
into the weekend, but there appears to be at least some
potential for showers to work their way back into the forecast
for the Friday-Saturday timeframe.
&&
.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
00z update... A very dry air mass, given the prevalence of high
pressure at the surface and aloft, will maintain generally
VFR/unrestricted conditions and light winds through the forecast
period.
Much like the last several nights/early mornings, a small fly
in the ointment is the potential for patchy valley fog. The
greatest confidence of such (60-70% confidence) early Sunday is
at KIPT, with lower degrees of confidence (20-40%) at KBFD and
KLNS.
Outlook...
Mon...AM Fog (Mainly N PA); otherwise VFR.
Mon night...Incr clds, SHRA poss W toward sunrise.
Tue...Sct SHRA. TSRA poss W & S late.
Tue PM...CFROPA. SHRA. TSRA poss. IFR fog poss mainly NW.
Wed...Sct AM SHRA SE. Otherwise becoming VFR.
Thu...AM fog then VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Lambert/Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Colbert/Bauco
AVIATION...Jurewicz/Dangelo

NWS CTP Office Area Forecast Discussion