447
FXUS61 KCTP 170756
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
356 AM EDT Sun Aug 17 2025

.SYNOPSIS...
* Very warm and humid end to the weekend with isolated to widely
  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 /THROUGH TONIGHT/...
Hires ensemble model output brings ongoing convection tracking
eastward from the thumb of lower MI over southern Ontario
across Lake Erie into the northwest/western Alleghenies btwn
11-16Z. Focus should then shift downwind of the mtns across the
central ridges and eastern valleys where seasonably high
moisture content/higher pwat air and strong boundary layer
heating along a pre frontal/lee sfc trough may contribute to an
environment supportive of strong to marginally severe
thunderstorm wind gusts. Inverted-V fcst soundings and heavy
precip loading could aid in mixing down a few locally damaging
wind gusts. Weak (<30kt) mean sfc-500mb shear values preclude a
more organized severe storm threat. SPC has narrowed the D1 SWO
to only include the southeastern portion of CPA near and to the
southeast of the I-81 corridor. Most likely timing would be late
afternoon-evening or btwn 20-01Z.

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,
enhanced runoff or flooding issues should remain fairly isolated
and a low probability outcome.

Today will likely be the warmest day in the next 7 (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. Min temps
will be about 10 degrees lower night/night along the northern
tier with predawn readings Monday around 50F.

&&

.SHORT TERM /MONDAY 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 HP
drifting over eastern Canada. NBM precip signal looks somewhat
overdone and may be more of an easterly flow low cloud signal
particularly in the southeastern portion of the forecast area.
This is also where NBM projects the "coolest" daytime max temps
AOB 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 nadir 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 SATURDAY/...
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 /07Z SUNDAY THROUGH THURSDAY/...
Decreasing winds are expected overnight with calm to light and
variable winds across central Pennsylvania. Patchy valley fog
formation is expected in the 06Z-12Z Sunday timeframe; however,
restrictions at terminals will be limited towards IPT based on
a combination of GLAMP/HREF guidance. Decaying showers expected
to enter western Pennsylvania early this morning, with higher
chances (~50-60%) of SHRA making it into BFD/JST slightly after
sunrise. Restrictions probabilities remain low with these batch
of showers; however, some relatively lower ceilings (still
above MVFR thresholds) could sneak into the western terminals
before coverage decays.

Model guidance indicates a broken line of showers with isolated
TSRA making way into central Pennsylvania entering western
terminals slightly after 18Z Sunday (BFD/JST) and continuing on
an eastward progression, reaching MDT/LNS ~02/03Z Monday. There
will also be some potential for scattered SHRA/TSRA to form
ahead of this broken line, mainly impacting IPT/MDL/LNS. Recent
HREF guidance does indicate some locally heavy rainfall within
showers and thunderstorms that could bring about localized drops
in visibility; however, impacts at airfields remain low
confidence (~20-30%) at this timeframe. Have began to introduce
PROB30 groups for the airfields at most risk for thunderstorms
this afternoon; however, still quite a bit of remaining
uncertainty with respect to timing/coverage of TSRA.

Outlook...

Mon...Mainly VFR, Isolated PM SHRA/TSRA possible far south.

Tue-Thu...Chc of SHRA/TSRA areawide.

&&

.CLIMATE...
The high temperature at Bradford was 86 degrees on August 16th,
which tied the record high temperature set back in 1987.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Steinbugl
LONG TERM...Steinbugl
AVIATION...NPB
CLIMATE...NPB