Williams Run Reservoir Pennsylvania Weather Forecast Discussion

424
FXUS61 KCTP 151124
AFDCTP
Area Forecast Discussion
National Weather Service State College PA
724 AM EDT Wed Oct 15 2025
.SYNOPSIS...
* Seasonably cool & dry with near/below average temps Wed-Fri
* Modest warming trend/above average temperatures this weekend
* Weekend starts dry and ends wet; breezy conditions and periods
  of rain Sunday into Monday
&&
.NEAR TERM /THROUGH TONIGHT/...
Quick/minor update to account for staying power of shower band
moving across the NW Alleghenies. Radar trends suggest it should
fizzle out as it approaches I-80, but could certainly see a few
early to mid morning sprinkles as far south as State College.
Previous Discussion Issued: 339 AM EDT Wed Oct 15 2025
IR satellite shows clouds across the NW 1/2 of CPA behind a
weak, moisture-starved cold front. Valley fog has also developed
across the mid Susq region from LHV to IPT to SEG. Similar to
last night, guidance was too bearish (cold) with minimum temps
for the immediate term overnight->early morning period. We still
can`t rule out a spotty shower downwind of Lake Erie through
daybreak - and upstream radar trends would broadly support that
idea; otherwise expect partly to mostly cloudy skies into
midday before clouds clear/dissipate from north to south and
a northerly breeze increases this afternoon. Max temps range
from the upper 50s in the northern tier/Endless Mtns to the
upper 60s in the lower elevations along the MD line. Clear and
colder tonight (about 10-15 degrees colder than last night) with
min temps in the 30-40F range NW to SE. Areas of frost will be
largely confined to areas where the growing season has
officially ended; therefore no frost advy headline will be
issued (see the latest PNSCTP on end of growing season).
&&
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Sunny and seasonably cool/breezy on Thursday. Daytime dryness
will peak on Thursday with room for downside to minRH in the
25-35% range. P-gradient between exiting storm in the North
Atlantic and high pressure migrating to the southeast from the
Upper Great Lakes will result in 20-30 mph wind gusts focused
over the eastern portion of the forecast area. The low humidity
and breezy conditions could support a more active fire wx day
with an elevated risk of wildfire spread (SPS considerations
pending fine dead fuel moisture assessment and coordination
with PA BOF/DCNR partners).
Minimum temperatures will reach a short term nadir Thursday
night with frost/freeze conditions probable across the majority
of CPA early Friday morning. Fcst low temps range from 25F in
the usually colder spots in the NW Alleghenies to around 40F in
the Harrisburg metro. Frost advy is likely going to be needed
for some (if not all) of the 7 zones in the LSV where the
growing season remains active; will continue to highlight this
in the HWO. Again, no frost/freeze headlines for zones where the
growing season has ended.
Sfc ridge axis migrates slowly eastward Friday reaching eastern
PA by 12Z Saturday. This should allow for one more chilly night
particularly in the eastern valleys. Clouds are likely on the
increase over western PA by the end of the period as WAA pattern
and LLJ ramps up into the Upper Ohio Valley.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
Trending milder through the weekend with max temps 60-70F
behind an increasing southerly return flow on the backside of
departing sfc high pressure. Latest model data continues to
favor mainly dry wx through Saturday.
Within a highly amplified 500mb flow pattern, a strong upper
trough and well defined frontal system should tap Gulf moisture
moving east of the Mississippi River by late in the weekend.
This system will most likely bring rain to CPA Sunday through
Sunday night/Monday.
Onset timing of rain is fairly uniform amongst the guidance
which correlates well to NBM, but the precip duration and
intensity become less certain with time given the growing model
spread into early next week. Interestingly, the 15/01Z NBM
clusters well with the 15/00Z EC and 15/06Z WPC QPF generally
agrees as well. The last 2 runs of the EC remained very
deep/closed and much slower which is a stark contrast from the
more progressive GFS and CMC solutions. While the details get
ironed out at shorter forecast lengths, the Sunday-early next
week timeframe will feature the highest odds of widespread
rainfall in the next 10 days.
&&
.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Lower CIGS did make it to the UNV area for a brief time.
Also some fog and lower CIGS at times into IPT.
Overall a lot of variation. Will continue to adjust fcst
as needed this morning.
Earlier discussion below.
Most of the area now clear. Some lower CIGS still at BFD.
Winds kicking up at times across the higher elevation sites
of BFD, JST, and AOO. However, winds likely to weaken again as
temperatures cool more.
Expect skies to clear at BFD at mid morning, as a cold front
drops southward today, and drier air works into the area.
Also the pressure gradient increases, so winds will become
gusty at times later today.
Not looking at much cloud cover off the lakes later today and
overnight tonight, given the low level flow is from the
northeast, and the colder air is not very deep.
Expect winds to become gusty again on Thursday, given the
gradient.
Outlook...
Thu...VFR, still breezy.
Fri-Sat... VFR
Sun...Restrictions possible in SHRA. Low probability of a
thunderstorm over northwest PA.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...Martin

NWS CTP Office Area Forecast Discussion