Lancaster, Pennsylvania 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

912
FXUS61 KCTP 260705
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
305 AM EDT Tue May 26 2026

.WHAT HAS CHANGED...
* Fog has begun to form across the area, especially south of
  I-80. However, there is a medium uncertainty on just how dense
  and widespread the fog will get before morning.

&&

.KEY MESSAGES...
1) Fog may be dense this morning. Advisory possible-likely.

2) Rain chances through mid-week with considerable cloudiness
across much of the region today and Wednesday.

3) Tranquil weather conditions emerge in the latter stages of
the week and continue into the final weekend of May.

&&

.DISCUSSION...
KEY MESSAGE 1: Fog may be dense this morning. Advisory possible-
likely.

Early morning nighttime microphysics sat loop shows a rapidly
expanding area of fog filling in the valleys first. Visby
bouncing somewhat at observation sites. But, the general trend
is that the fog is becoming more widespread. The high clouds are
less of an issue for forecasting the fog than the mid-low clouds
which are expanding NE from southwestern PA into the Laurels and
south-central mtns. This cloud deck will be a big player in just
how widespread the fog will get. However, the northern tier is
also filling in with river valley fog, too, and they have
virtually no impediments toward fog stopping. BFD and N38 have
already seen their Td go down by 5F in the last 1-3 hrs. Despite
the drier air up there, the temps have cooled off to meet their
cross-over temps. Overall, the widespread fog is likely to be
most impactful between UNV-SEG-MDT, but even there, the low-
ish clouds could thwart the best efforts of fog to get <=1/4SM.
Also, the nrn tier valleys have nothing stopping them from
getting worse. Will continue to monitor fog for the need for an
Advisory. Thinking is that we will eventually need one, but for
what area(s)?

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KEY MESSAGE 2: Rain chances through mid-week with considerable
cloudiness across much of the region tomorrow and Wednesday.

Front stalling just to the south of PA will keep a focusing
mechanism close and force the mention of SHRA today, tonight and
Wednesday across the southern half of the CWA. After the fog
starts to burn off, the moisture and ridgetops may combine to
pop the first SHRA of the day. A sfc wave rolling along the
stalled front will help make numerous showers (and a couple of
thunderstorms) tonight and Wednesday. A mainly-dry cold front
then drops down from the N and brings drier, cooler air for
Thursday. Despite the current lack of moisture along this
feature, models continue to pop sct SHRA over NErn PA Wed
aftn/evening. So, we can`t get rid of the PoPs there.

The greatest liklihood for showers is still S of I-80, esp S of
US Rte 22 on Wednesday. Cloud cover yields a low confidence in
TS formation, as the temps may stay too chilly to allow for deep
convection both today and Wed.

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KEY MESSAGE 3: Tranquil weather conditions emerge in the latter
stages of the week and continue into the final weekend of May.

A reinforcing ridge of high pressure will push another cold
front through the Commonwealth on Thursday. Behind it, cooler
temperatures and brighter skies will follow. High pressure
should ensure a much more pleasant last weekend of May than
we`ve had this Memorial Day weekend. Lows in the 40s to 50s and
highs in the 60s to 70s will be within a few degrees of average
conditions this time of year. Dewpoints will also drop back to
spring-like ranges and will feel quite comfortable. It will be
a great weekend for planting flowers if you haven`t gotten
anything in the ground yet. In fact, it will be an ideal weekend
for about any outdoor activity you can think of.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
High clouds have largely cleared out across Pennsylvania and
areas of valley fog are beginning to develop. The fog may be
locally dense, with visibility potentially dropping to as low
as 1/4SM. There is significant uncertainty regarding the extent
and magnitude of visibility restrictions, but there is at least
some chance that all TAF sites see IFR/LIFR visibility at some
point through the rest of the night as the fog continues to
expand.

VFR conditions will return by mid morning as the fog mixes out,
giving way to scattered clouds between 3500 and 5000 feet for
much of the day. A few showers will likely develop near JST and
AOO during the afternoon, potentially bringing brief periods of
MVFR ceilings to those sites.

Southerly flow will usher in increasing low-level moisture
Tuesday night, likely resulting in increasing low clouds. MVFR
ceilings will develop from south to north after 00Z, with IFR
possible after 06Z.

Outlook...

Wed...Mainly VFR, some scattered SHRA could bring restrictions.

Thu-Sat...VFR with no significant weather expected.

&&

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

&&

$$

WHAT HAS CHANGED...Dangelo
KEY MESSAGES...Lambert/Beaty
DISCUSSION...Lambert/Dangelo/Beaty
AVIATION...Bauco