Halls, Pennsylvania Weather Forecast Discussion

496
FXUS61 KCTP 170548
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
148 AM EDT Wed Sep 17 2025
.SYNOPSIS...
* Increasing clouds across the region tonight and Wednesday with
  cooler temperatures Wednesday afternoon.
* Periods of light rain will continue across southeastern
  Pennsylvania through Wednesday night; accumulations generally
  0.1-0.25 inches.
* Dry conditions return areawide on Thursday and will persist through
  the weekend.
&&
.NEAR TERM /THROUGH TODAY/...
A coastal low pressure system is currently located off the
coast of Virginia and continues to produce a shield of cloudy
skies extending into northern PA this evening. Periods of light
rain continue to rotate counter clockwise around the low,
bringing occasional showers to portions of southeast
Pennsylvania. Very dry air at the surface characterized by
dewpoints in the mid 50s has limited the amount of rainfall
making it to the surface thus far.
Overnight, clouds will continue to expand northwestward as rain
continues. Low clouds are progged to reach I-80/I-99 by
daybreak, limiting fog potential south and east of there.
Farther north, some valley fog formation is expected once again.
Lows will range from the upper 40s in northwest PA to near 60 in
the southeast.
On Wednesday, thickening clouds and persistent easterly flow
will keep temperatures significantly cooler than recent days
east of the mountains. Highs should stay in the upper 60s to
near 70s along south/east of I-99/I-80, while locations farther
west soar into the 80s where skies should be mostly sunny or
partly cloudy. Periods of rain will continue to affect southeast
PA on Wednesday as dewpoints gradually increase. Dewpoints will
crest the 60F mark for the first time in quite awhile as
tropical moisture swirls into the region accompanied by PWATs
over 1.5". If you look at radar on Wednesday, you may see
returns extending into northern PA (north of I-80). Dry air at
the surface should prevent most of the rain from reaching the
surface there, though. Rainfall totals by Wednesday evening
should remain below 0.5" for most, and little to no accumulation
is expected along south/east of I-80/I-99.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY/...
The surface low will move east of the area Wednesday night as
surface high pressure beneath a blocking ridge of high pressure
works its way back into the region. Cool afternoon highs and
relatively high dewpoints combined with clearing skies in the
wake of the low will promote widespread fog formation into
Thursday morning. Satellite imagery over Central PA at daybreak
will be quite striking as most valleys are blanketed with fog.
Thursday and Friday will be a continuation of what we`ve seen
for a majority of the past couple weeks with plenty of sunshine,
seasonably mild temperatures, and light winds. It will take a
little while for the moisture in southeast PA to be replaced by
a drier airmass, so expect the air to feel a bit humid still on
Thursday. Highs will generally be in the 80s with lows in the
upper 40s (NW) to lower 60s (SE). A backdoor, moisture-deprived
cold front will sag south into northern Pennsylvania Friday
afternoon, with an increase in cloud cover north of US-6 being
the only noteworthy aspect of its arrival. Drier air awaits in
its wake...
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
On Friday night, the aforementioned backdoor cold front will
slide through Pennsylvania with a strong 1028mb high surging in
behind it. Dewpoints will plummet by Saturday morning,
supporting a return to below-normal overnight temperatures with
clear skies and calm winds. Surface high pressure will set up
off the New England Coast for the weekend, ensuring moist
southeast flow and tranquil weather. Highs will tick down a few
degrees for the weekend, with highs in the 70s and lows in the
50s most likely at this time.
Heading into next week, high pressure will begin to lose its
grip on the region as an upper trough tries to disrupt the
persistent ridge of high pressure aloft. Still plenty of
uncertainty on how much, if any, precipitation will get into
Pennsylvania but southerly flow ahead of the approaching system
will support continued warmer than average temperatures for the
start of Astronomical fall.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Showers will continue to rotate into southeastern PA on the
northwestern side of a low pressure system currently located
east of Maryland and will continue to impact MDT and LNS for
much of the night. Ceilings will gradually lower at these two
sites as well, with most guidance showing MVFR ceilings
developing in the 08-10Z timeframe. The GLAMP continues to
suggest that a prolonged period of IFR ceilings will be
possible, particularly at LNS, but most model RH profiles show a
shorter window between 15Z and 21Z where cloud bases are more
likely to drop below 1000 feet AGL.
Showers gradually expand northward through the day and may
reach as far north and west as UNV and IPT. Those sites, along
with AOO, may see a period of MVFR ceilings as showers approach,
but confidence is not high on that occurring. Instability is
forecast to be very weak, so we will continue to keep thunder
out of the TAFs for now. Winds will generally be out of the
northeast at 5 to 10 knots with a few gusts to 15 knots
possible in southeast PA. Showers gradually shift eastward as
the low moves away from the area, and will come to an end by
00Z.
Widespread fog formation appears likely across much of the area,
with IFR visibilities possible at most TAF sites after 06Z. Low
clouds will persist across southeast PA through much of the
night and ceilings are expected to drop back to IFR at MDT and
LNS.
Outlook...
Thu...Generally VFR.
Fri-Sun...VFR with AM valley fog.
&&
.CLIMATE...
Astronomical fall officially begins with the autumnal equinox
on Monday, September 22, 2025 @ 2:19 p.m. EDT. The Autumn 2025
season will last 89 days, 20 hours, and 43 minutes. Daylight
saving time will end just after Halloween with clocks falling
back at 2 a.m. Sunday, November 2, 2025.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Banghoff
NEAR TERM...Banghoff
SHORT TERM...Banghoff
LONG TERM...Banghoff
AVIATION...Bauco
CLIMATE...Steinbugl

NWS CTP Office Area Forecast Discussion