342
FXUS61 KCTP 121818
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
218 PM EDT Sat Sep 12 2026

.WHAT HAS CHANGED...
* Issued a Flood Watch (4 PM today to 4 AM Sunday)for the
  potential of locally up to 2-4 inches of rain and Flash
  Flooding.

&&

.KEY MESSAGES...
1) Numerous showers and thunderstorms developing over/moving
into the NW Mtns and Laurel Highlands could bring locally over 2
inches of rain and some areas of flash flooding late today into
early Sunday.

&&

.DISCUSSION...
KEY MESSAGE 1: Numerous showers and thunderstorms developing
over/moving into the NW Mtns and Laurel Highlands could bring
locally over 2 inches of rain and some areas of flash flooding
late today into early Sunday.

A juicy airmass (with PWAT values peaking between 1.5 and 2
inches), a prominent zone/axis of llvl streamline/theta-E
convergence and the eastern edge of moderately high MU CAPE
values over 1000 J/KG will focus the heaviest rain over the next
18-24 hours across the Laurel Highlands and NW Mtns. The past
several runs of the HREF and its high res members have been
homing in on our western zones with 6 hour PMM values of 2-3+
inches, which is near or slightly hours than 6 hour FFG values.

Previous...

Expect showers and storms to form later this afternoon into
Sunday morning, as warm advection brings back the
aforementioned, much more humid airmass.

This will be followed by more showers and storms later Sunday
afternoon and evening, as stronger dynamics and cold front
work on the humid airmass.

Not a lot cold advection, abnormally warm and moist air
take aim at the Great Lakes area again on Tuesday, as a
strong upper level ridge builds northward from the TN Vly.

ERO for today adjusted to one area, and SPC outlook for
Sunday trimmed across the southeast. Complex fcst, as been
the case this summer.

Still holding off on a flood watch for now, given nothing
going on yet on radar, still time to see how things play out
later this aft.

More information below.

Guidance does put numerous heavy bands of rain over the area.
FFG lower west and north, but heaviest QPF could be to the
east. Also maybe things more an issue later Sunday, depending
on where that rain falls today.

Again, the problem is: where? With uncertainty high as it is
and FFG getting higher slowly, still holding off.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...

Moisture is streaming in from the south early this afternoon
(PWATs 1.5-2"), leading to MVFR ceilings remaining in place
along and around the Allegheny front. An area of clearing in
southwest PA is slowly eroding away at this lower ceiling deck
which may lift terminals like JST and UNV to VFR in the coming
hours. Cloudy conditions will likely remain across most other
terminals though ahead of precipitation this evening.

Building instability from the aforementioned area of clearing
will allow for thunderstorm development in the 20Z-22Z timeframe
in Western PA. Have adjusted PROB30 groups to reflect latest
confidence in timing of potential airfield impacts. Given the
scattered, possibly repeating, nature of these storms,
uncertainty in exact timing is still high enough to not include
any TEMPO groups at this time.

The best overlap of instability and high PWATs appears to be at
BFD, JST, and AOO. This is where the strongest storms with the
heaviest rainfall, gusty winds, and visibility impacts are
likeliest. Given the cloudier conditions further east limiting
instability growth, showers and thunderstorms` are expected to
be weaker. Some heavy downpours remain possible after sunset
though given the high PWATs, so included visibility restrictions
PROB30s elsewhere too.

The influx of low level moisture will also contribute to low
ceilings tonight. Included prevailing IFR ceilings at all TAF
sites in the wake of storms and showers moving through. Heaviest
restrictions are most likely to come in the form of low
ceilings and mist with for the most part with low ceilings
lasting into tomorrow morning. However, clearing skies around
sunrise at BFD, JST, and AOO may lead to some fog development
early tomorrow morning.

Outlook...

Sun...Early MVFR/IFR and moderate rainshowers across the state.
Additional SHRA/TSRA in the afternoon.

Mon...Primarily VFR conditions, with some potential for
afternoon SHRA/TSRA.

Tue-Thur...Mainly VFR with a showers possible over NW PA.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late tonight for PAZ004-005-010-011-017-
024-033.

&&

$$

WHAT HAS CHANGED...Lambert/Dangelo/Martin
KEY MESSAGES...Lambert/Dangelo/Martin
DISCUSSION...Lambert/Dangelo/Martin
AVIATION...Lambrech