Spruce Hill, Pennsylvania Weather Forecast Discussion

722
FXUS61 KCTP 242328
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
728 PM EDT Wed Sep 24 2025
.SYNOPSIS...
* Muggy with periods of much needed rain through Thursday
* Drying out and not as humid on Friday
* Above average temperatures forecast through the end of
  September; however rainfall potential remains low/uncertain
&&
.NEAR TERM /THROUGH THURSDAY/...
Another mostly cloudy and muggy period with rain showers
expected to expand from SW to NE across CPA into tonight. The
clouds have kept instability and rain rates in-check so far, but
can`t rule out a couple of heavy downpours this evening or
overnight as above normal PWs creep higher in response to an
increasing SSWly LLJ. Very warm and humid conditions for late
September with low temps +15-20 degrees above climo in the
60-70F range.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
A broad upper low over the OH Valley will gradually devolve into a
positive-tilt trough before moving eastward over the Northeast
Thursday. At the surface, a weak low will traverse the St Lawrence
Valley dragging a cold front the OH Valley and Appalachians.
Expanding shower/thunderstorm activity and extensive low cloud
cover is probable Thursday morning ahead of the cold front.
With widespread clouds, minimal surface heating and poor lapse
rates are expected over much of the warm sector. Still, a very
moist air mass for late Sept. with 60s to 70s F dewpoints
should support some weak buoyancy (MLCAPE generally less than
1000 J/kg). Southwesterly flow aloft will favor slightly
cyclonically curved hodographs with around 30-40 kt of deep-
layer shear. This could support some storm organization ahead of
the front into linear clusters with transient updraft rotation.
Isolated damaging gusts are the most likely threat, though a
brief QLCS tornado is also possible near the effective front
where low level flow is more backed. However, given the limited
buoyancy and marginal storm organization, a broader severe risk
appears unlikely. SPC maintained a MRGL severe tstm risk across
the southeast portion of the area with a 2% tornado prob. Hi
pwats around 2" could also support another round of locally
heavy rain focused over the eastern half of the CWA.
The +tilt northern stream trough tracks across NY state early
Friday with the cold front reaching the coast by 12Z. There may
be a couple of lingering showers with the upper trough passage,
but on balance conditions should dry out through Friday night as
weak area of high pressure migrates eastward from the Great
Lakes. A wind shift to the WNW should advect slightly drier/less
humid air into the area to end the week with more
comfortable/seasonable min temps in the 45-60F range Friday
night.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Model and ensemble data show a highly complex pattern evolving
over the Eastern U.S. this weekend into the final days of
September. A southern stream cut-off low over the central
Appalachians will interact with a pair of tropical systems over
the western Atlantic. While the details remain unclear, there
is general agreement with a plume of deep tropical moisture
being transported northward along the coast into the northern
mid Atlantic region. An easterly component to the low level flow
suggests more clouds and increasing odds for rain particularly
over the southern half of CPA this weekend into early next week.
There are signs of drier weather pattern unfolding by the time
the calendar flips to October.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Most of showers will lift northward overnight, with just a few
showers left over. This is based on a weak low tracking northeast
across western NY overnight, with warm front over Lake Erie,
along with the main push of higher dewpoint air lifting
northward across PA from the far south. Had a few small bow
shape showers near the MD border up to a short time ago, given
how high the dewpoints are down there. Anyway, the main thing
overnight will be a wide range of conditions, but the trend will
be for lower conditions late.
Conditions will improve on Thurday, as winds shift more to the
southwest. Went with showers for now, potential for storms, but
a bit too far out to add this detail.
Improving conditions on Friday, as slightly drier air works
into the area.
Outlook...
Fri...Low cigs early trending VFR by Friday afternoon.
Decreasing odds for rain.
Sat-Mon...Low confidence in sub-VFR cigs/rain across the
southern/eastern portions of the airspace. Mainly VFR to the NW.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...Martin

NWS CTP Office Area Forecast Discussion