Lancaster Junction, Pennsylvania Weather Forecast Discussion

260
FXUS61 KCTP 031823
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
223 PM EDT Fri Oct 3 2025
.SYNOPSIS...
* Dry with well-above average temperatures this weekend and
  into the beginning of next week.
* Cold frontal passage brings showers on Tuesday/Wednesday.
* Dry conditions again later next week with low temperatures
  approaching the freezing mark.
&&
.NEAR TERM /THROUGH TONIGHT/...
Clouds (tiny cu NW and SE and high clouds S) should dissipate
and slide away before or around sunset. Wind goes calm and stays
that way. Fog is then expected to form in the valleys, not
widespread, but more than Fri AM. The West Br and tribs to it
have the best chc of having fog overnight. Temps should stay
just 3-5F milder than the prev night but dewpoints will also be
a notch higher. Coldest spots will dip to around 40F, and most
will be 45-50F.
&&
.SHORT TERM /SATURDAY/...
WYSIWYG. More of the same Sat. After fog goes away: sunny and
very warm for Oct. 8H temps of +12-15C will mix down to hit 80F
over half the land mass of Central PA. Those are more like late
June or early Aug highs. The higher elevations stay below that
mark. Records are generally 5+F greater than the forecast highs,
though. GFS is much weaker with the inversion than NAM. The
weak inversion is a good signal for a dewpoint bomb/drop during
the day. But, without support from NAM and HREF mean, don`t want
to go too wild with a departure from guidance. But, did nudge
mid- day/aftn dewpoints down a few degs from NBM, esp in the
mtns and Lower Susq.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The dry pattern throughout the short-term forecast period
appears to trend wetter with the approach of a surface low
pressure from the central US, which will track northeastward
into Ontario. The low will drag a cold front through the area
in the Tuesday/Wednesday timeframe, bringing some beneficial
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 0.3 inches in northwest PA, with lesser
amounts as you move south and east, but some of the
deterministic guidance, namely the 12Z GFS, continues to show
the potential for upwards of 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. 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.
&&
.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Tiny cu popping up over the NW and SE and only high clouds over
the S which are moving S at 18Z. VFR should continue with a
light S/SW wind at most airfields. BFD wind is out of line with
others (34006KT) at the moment, likely due to the convective
current related to the tiny cu building nearby. The cu may
dissipate as we mix a little deeper, but should definitely go
away as sunset nears. Air calms down around sunset and stays
calm the rest of the night. Cloud cover should be much less than
the high clouds we had last night, so there should be excellent
radiational cooling without wind. Expect fog to form in the
valleys, likely more widespread than Fri AM. Have mentioned IFR
fog for a few hours at IPT (most likely) and AOO, but UNV has
much lower chc (20%) of dipping to IFR. Still mentioned it
there, though. BFD may get a little fog in the late
evening/early night, but probably go back to VFR for the balance
of the night as the coldest air slides off into the deep valleys
nearby. Sat will be VFR after the fog (and any little bit of low
stratus near the fog) dissipates. The center of the sfc high
will be close enough to keep the wind very light and out of the
S/SW again. More of the same for Sun and Mon.
Outlook...
Sun-Mon...AM Fog (Mainly N PA); otherwise VFR.
Tue...Sct SHRA.
Tue PM...CFROPA. SHRA. TSRA poss. IFR fog poss mainly NW.
Wed...Sct AM SHRA SE. Otherwise becoming VFR.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Dangelo/NPB
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Bauco/NPB
AVIATION...Dangelo

NWS CTP Office Area Forecast Discussion