361
FXUS61 KCTP 201113
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
713 AM EDT Wed Aug 20 2025

.SYNOPSIS...
* A warm/cold front tandem arrives from eastern Ohio today and
  brings numerous showers and isolated to scattered
  thunderstorms.
* High pressure over eastern Canada will help keep Erin offshore
  and PA dry as the hurricane passes our latitude.
* A refreshing taste of Fall likely to arrive into the last
  week of August

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Widespread stratus and stratocu within a llvl cold air damming
regime led to overnight min temps generally in the low to mid
60s across the CWA.

Increasing low to mid level theta-E advection aimed at our
Central and NW Mtns was supporting an area of showers and a few
TSRa across Western PA INVOF of a sfc quasi-stnry front banked
up along the Western Ridges of the Laurels and NW Mtns.

The narrow warm sector to the west of this front will shrink
further as a cold front catches up from the west and occludes as
it enters/slowly moves across the central part of our CWA late
this morning and this afternoon, before stalling and
transitioning into more of a stationary front/inverted trough
thanks to increasing influence and deepening easterly flow to
the north/northwest of Hurricane Erin that will be centered
about 250 NM SE of Cape Hatteras NC early Thursday morning.

The increasingly focused low to mid level theta-E convergence
(near and just to the NW of the highest PWAT values of 1.75 to
2.0 inches across the Mid and Lower Susq Valley) could lead to
some highly localized 1-2 inch rainfall totals over a 6-12 hour
period, which should be handled fairly well as a result of much
higher FFG values over that time interval.

Nonetheless, a low probability for amounts heavier than this
prompted WPC to blanket much of the CWA with a a MRGL Risk for
excessive rain this afternoon into tonight. We will highlight
this in our Hazardous Weather Outlook (HWO) and Social Media
platforms at this point.

High temps today will only reach the mid and upper 60s across
the Mtns North and East of KIPT with upper 70s to low 80s across
the Southern Tier counties of the state.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
Lingering forcing and boundaries for the overnight keeps
SHRA/isold TSRA in the forecast until dry air moves in from the
NE.

Lows overnight tonight will be nearly identical to temps we`re
seeing early this Wed morning - which is mid to upper 50s
across the Northern Tier and low to mid 60s elsewhere.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Confidence is high for the long range. Large scale subsidence
to the west of departing Hurricane Erin provides a mainly dry
Thurs and all dry Fri. Erin passes well to the east of PA with
max wind only 12KT with gusts under 20KT in Lancaster Co Thurs.
Rising heights into the weekend will promote a warming trend
with highs rebounding back into the lower 80s for Friday and
through the whole weekend.

Longer range model and ensemble data continues to show a more
formidable upper trough digging into the Great Lakes and
amplifying this weekend over the Eastern U.S. Moisture
returning northward from the Gulf along the leading frontal
boundary should provide a focus for showers and storms with max
POPs Sat-Sun as it moves slowly eastward from the Appalachians
toward the Mid Atlantic coast.

Taste of Fall on the horizon for at least the first part of next
week as cooler/more refreshing air filters into the region from
Canada.

&&

.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
Current radar depicts showers across generally confined to the
northeastern edge of the airspace, likely only impacting IPT
over the next hour before drifting further east. Guidance
continues to indicate that the current low-level cloud deck will
remain fairly persistent throughout much of the day. Recent
GLAMP guidance does indicate slight improvements in the
afternoon/evening hours across south-central (AOO) and
southeastern (MDT/LNS) terminals with MVFR being the most
plausible solution given recent RAP model soundings and GLAMP
model guidance. Low clouds are expected to prevail once again
after 00Z Thursday with high confidence, especially after 06Z
Thursday, where widespread IFR-to-LIFR conditions are progged by
the bulk of model guidance.

The less certain portion of the TAFs come with respect to
precipitation chances this afternoon/evening. Current radar
trends do outline some windows of opportunity for (relatively)
dry conditions, thus have combined these trends with current
model guidance in order to gauge those windows with low-to-
moderate (~30-50%) confidence. Further SHRA development is
expected to continue over the next couple of hours; however,
given recent radar trends looking like SHRA will shoot the gaps
between JST/AOO and UNV, have limited mentions in the near-term
(through 18Z Wednesday). Coverage of SHRA/TSRA becomes more
uncertain after 18Z-06Z, with GLAMP guidance indicating little
in the way of precipitation; however, HREF/NBM remain fairly
consistent with respect to SHRA coverage, thus have included
PROB30s timing out shower activity this afternoon/evening. At
this time, isolated TSRA seem the most plausible, with
confidence too low for inclusion in the 12Z TAF package.

Outlook...

Fri-Sat...VFR. AM fog possible.

Sun...T-storms likely.

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert/Bauco
SHORT TERM...Lambert/Dangelo
LONG TERM...Dangelo/Steinbugl
AVIATION...NPB