404
FXUS61 KCTP 181006
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
606 AM EDT Fri Sep 18 2026

.WHAT HAS CHANGED...
* No sig changes

&&

.KEY MESSAGES...
1) Becoming noticeably less humid through the day today with
cooler air settling in for tonight.

2) Rain returning by Sunday, heavy at times.

3) Rainy pattern continues into much of next week.

&&

.DISCUSSION...
KEY MESSAGE 1: Becoming noticeably less humid through the day
today with cooler air settling in for tonight.

With the cold front now pushing into the southern tier, high
clouds are peeling off to the south. However, moisture remains
trapped in the boundary layer resulting in widespread stratus
and a few areas of fog. Dewpoints range from the upper 60s to
the low 70s in these predawn hours. Showers are expected to
remain isolated at best. A north breeze with gusts up to 20 mph
will advect a cooler and drier air mass, with temps and dewpts
in the 40s for central PA by late tonight. Patchy valley fog is
possible early Saturday morning. Most, if not all of Saturday
will be dry.

-------------------------------------------------------------

KEY MESSAGE 2: Rain returning by Sunday, heavy at times.

Periods of potentially heavy rainfall are expected Saturday
night into Sunday. Both NAEFS and ECMWF SATs show at least 90th
percentile PWs returning to the region, which is supportive of
at least a marginal excessive rain signal. A surface low
expected to track over the Great Lakes will usher in this
moisture and more than enough forcing for widespread
precipitation. A few to several hundred J/kg of MUCAPE should
support some heavier downpours, but little to no CAPE above the
-10C level suggests the lightning threat will be limited. Most
 likely rainfall amounts with the Sunday system are 0.50-1.50".


-------------------------------------------------------------

KEY MESSAGE 3: Rainy pattern continues into much of next week.

PoPs are progged to drop into the 30-40 pct range on Monday as
high pressure wedges in from the north. However, the jet stream
will remain active and amplified with Pacific disturbances
moving across the nation. By Tuesday, most guidance has a slow
moving trough in the Ohio Valley advecting warm air above a
wedge of cool sfc air in place from the aforementioned high
pressure system. This setup may linger for a few days, with up
to several inches of rainfall possible through the week. The
cold air damming will also result in high temps only in the 50s
to low 60s.


&&

.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
Abundant moisture (PWATs of 1.5-2", in the 90-95th percentile
for this time of year) ahead of a cold front approaching from
the north will result in periods of mainly MVFR-IFR ceilings
across the region overnight. Higher confidence in periods of IFR
is for the higher-terrain terminals (primarily KBFD/KJST, though
perhaps KIPT as well between the ridges, with lower confidence
in IFR with southeastern extent).

Flow will trend northerly during the day on Friday with winds
of around 10 kts as the front moves southward across the
Commonwealth, with low clouds dispersing through the
morning/afternoon as drier air filters in from the north. Spotty
showers may accompany this frontal passage, primarily over
KBFD/KJST/KAOO where subtle convergence along the ridgeline
could support shower development. Lightning seems unlikely with
these showers as mid-level subsidence above the low-level moist
layer will put a cap on the vertical development of showers,
with MUCAPE equilibrium levels (MUEL) looking to stay shy of the
freezing level (around 5 C, suggesting that showers will be too
shallow for lightning potential).

Behind the front, a high pressure will slide in across the
Northeastern US and New England region Friday night, helping to
keep drier air settled in at the low levels across central
Pennsylvania. Meanwhile, moisture will rebound aloft as a low
pressure system approaches from the Ohio Valley, with mid/high-
level clouds streaming overhead during the night.

Outlook...

Sat...AM valley fog and some MVFR ceilings S. Then VFR.

Sat night-Tuesday...Periods of rain/storms with MVFR likely
(70%) and IFR possible (30%) for short periods.

&&

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

&&

$$

WHAT HAS CHANGED...Colbert
KEY MESSAGES...Steinbugl/Colbert
DISCUSSION...Steinbugl/Colbert
AVIATION...Teare