313
FXUS61 KCTP 180908
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
508 AM EDT Tue Aug 18 2026

.WHAT HAS CHANGED...
* Dense Fog Advisory in effect until 9AM for Warren, McKean, and
  Elk County

&&

.KEY MESSAGES...
1) Patchy dense fog this morning gives way to a mostly sunny and
dry day.

2) An unsettled but not particularly wet period is expected mid
to late week.

&&

.DISCUSSION...
KEY MESSAGE 1: Patchy dense fog this morning gives way to a mostly sunny and
dry day.

Dewpoints are still in the mid 60s to low 70s this morning.
Mostly clear skies and light winds have resulted in thick fog in
the typical valley locations across northwest PA. The valley fog
is accompanied by some low stratus in the northwest mountains,
which is dropping visibility to a quarter mile or less across
much of Warren, McKean, and Elk County. As such, we hoisted a
Dense Fog Advisory there until 9AM.

With weak high pressure building over the region today, fog will
eventually mix out giving way to a very nice day. Dewpoints will
drop through the afternoon providing some relief from the
humidity. Scattered fair weather cumulus clouds will align
northwest to southeast along horizontal convective rolls this
afternoon before fading tonight with the loss of daytime
heating.

Lowering dewpoints tonight and an expectation of rain-free
conditions all day should make the chance for fog considerably
lower tonight. There could still be some patchy fog in the
deepest valleys, but most locations should stay cloud-free.

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

KEY MESSAGE 2: An unsettled but not particularly wet period is
expected mid to late week.

A short wave trough rotating around the base of the deep upper
low over Hudson & James Bays will be the next help to lift and
destabilize the air over PA by Wednesday. Expect some showers
to impinge upon Warren Co in the aftn on Wed and spread along
the NY border. Some of them could advance another county to the
south before daylight wanes and they die off. Precip chcs Wed
night and Thurs AM now look a little lower than previous
forecasts. But, isolated showers are still possible then.
Heights do dip for real on Thursday/night and will probably
develop a weak low pressure system to our south. That low will
push east to the sea Friday. Some light to moderate rain should
overrun the boundary to our south and make the southern half of
the CWA wet - but not too wet - on Thurs night and early Friday.
Model agreement lowers for the weekend, clouding the crystal
ball. PoPs end up at 40-50% Sat and Sun without confidence in
the forecast being either wet or dry.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
A much drier air mass is working its way into Pennsylvania
behind a cold front that moved through earlier, though
sufficient low-level moisture for fog and some low clouds will
stick around into the morning. The extent to which fog causes
impacts at TAF sites is a little uncertain, with most guidance
outside of the LAMP showing very little impact, but all
airfields have at least some chance of seeing IFR visibility
develop prior to sunrise.

Once any fog and low clouds dissipate after sunrise, expect VFR
conditions to persist through the rest of the TAF period. Winds
will be out of the northwest at 5 to 10 knots.

Outlook...

Wed... VFR conditions with restrictions from afternoon SHRA/TSRA
possible in the northwest early.

Thu... Afternoon SHRA/TSRA with brief restrictions possible.
Otherwise, VFR conditions.

Fri...Chance of SHRA across the south, restrictions possible,
otherwise dry.

Sat...Chance of SHRA statewide, restrictions possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM EDT this morning for PAZ004-005-
010.

&&

$$

WHAT HAS CHANGED...Banghoff
KEY MESSAGES...Dangelo/Banghoff
DISCUSSION...Dangelo/Banghoff
AVIATION...Bauco