801
FXUS61 KCTP 172343
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
743 PM EDT Sun Aug 17 2025

.SYNOPSIS...
* Very warm and humid end to the weekend with scattered
  thunderstorms; isolated damaging wind threat SE PA
* Not as warm early next week with best chance for rain on Wednesday
* Mainly dry with seasonable temperatures for late week as
  Hurricane Erin moves away from the East Coast

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
With a cold front moving southeastward from the Lake Erie
shoreline, seasonably high moisture content/higher pwat air and
strong boundary layer heating along a pre frontal/lee sfc
trough will contribute to the development of scattered heavy
downpours and thunderstorms this afternoon. Inverted-V fcst
soundings across south central PA, along with potential heavy
precip loading, could result in a few locally damaging
thunderstorm downbursts. Weak (<25kt) sfc-6km shear values
preclude a more organized severe storm threat. SPC maintains a
D1 MRGL SWO across the southeastern portion of CPA near and to
the southeast of the I-81 corridor. Most likely timing for a
severe storm would be late afternoon- evening or btwn 19-01Z.

WPC has also maintained a marginal risk for excessive rainfall;
however higher rain rates in t-storms should be relatively
brief due to more progressive storm motions. Given the recent
dry spell and return of abnormally dry D0 drought conditions,
excessive runoff or flooding issues should remain fairly
isolated and a low probability outcome.

Today will likely be the warmest day in the next 7 days (maybe
for the rest of the month?) with max temps peaking +5-10 degrees
above the historical average for mid/late August in the mid 80s
to low 90s across the central ridges and mid/lower Susquehanna
Valley.

Noticeably drier/less humid/relatively cooler air will arrive
via a northerly breeze behind the cold front tonight,
particularly north of I-80 where dewpoints will fall into the
50s and even upper 40s. Min temps will be about 10 degrees
lower night/night along the northern tier with predawn readings
Monday around 50F.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
The aforementioned frontal boundary will push south of the MD
line on Monday as llvl flow shifts to the east around sfc high
pressure drifting over eastern Canada. NBM precip signal looks
somewhat overdone and may be more of an easterly flow low
cloud/sprinkles signal particularly in the southeastern portion
of the forecast area. This is also where NBM projects the
"coolest" daytime max temps, around 75F or 15 to 20 degrees
cooler vs. Sunday!

Shortwave trough and associated wave of low pressure diving
southeast from the Great Lakes will bring a renewed chance of
showers and storms into midweek. However, increasing large
scale subsidence/pressure channeling down the Appalachians to
the west of Hurricane Erin and east of sfc low in the Great
Lakes appears to be dampening the model QPF signal; shifting it
farther to the west over the Great Lakes and Ohio Valley. This
emerging model output signal is reflected in the modified D3
(Tue) WPC ERO which no longer includes CPA.

Tuesday max temps would mark a weekly low with highs in the 70s
for most of the CWA or 5-10 degree below late August climo for
the central and eastern zones.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Drier trending fcst theme continues for Wednesday as the sfc
low weakens as it runs into subsidence zone on the westside of
Hurricane Erin. It`s not out of the question that the Wed-Fri
(much of next week for that matter) period ends up being mainly
dry.

Longer range model and ensemble data continues to show a more
formidable upper trough digging into the Great Lakes heading
into the last week of August. This would bring a better
opportunity for rain while also suppressing the late summer
heat/humidity.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
Any organized showers and convection are moving through the far
southeast corner of the area as a frontal boundary pushes them
southward. As the sun sets, expect any isolated (10% coverage)
of showers across northern PA to dissipate. Across the south, an
isolated shower can drop conditions to MVFR for a brief time.

As the frontal boundary pushes south overnight, winds with
transition to the north but remain generally less than 5 kts. A
weak upslope over the Laurel mountains can bring a few hour
period of IFR to low IFR in FG at KJST before sunrise.

In the cooler air on Monday, a general MVFR to VFR mid level OVC
will develop by late afternoon in all locations in northeast
flow aloft. There is a low chance (20% or less) of a brief -SHRA
but will hold off on any timing this far out into the forecast.

Outlook...

Tue-Fri...Chc of SHRA/TSRA areawide but generally VFR.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl/Colbert
SHORT TERM...Steinbugl/Colbert
LONG TERM...Steinbugl
AVIATION...Tyburski