069
FXUS61 KCTP 270808
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
408 AM EDT Fri Sep 27 2024

.SYNOPSIS...

A nearly stationary front draped over PA will dissipate tonight.
Expect occasional light rain for southern PA through the middle
of next week, with a few periods of heavier rain and
thunderstorms possible. The heaviest rain over the next 5 days
is expected over south central PA which should be largely
beneficial. A shift toward drier/cooler weather is possible by
the end of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Drier air working in from the north is keeping things more-fair
there than over the southern half of the area. Low clouds and
fog prevail in the south as more light rain moves in from the
south this morning. The thicker clouds will work back over the
north in the afternoon. No signals for heavy rain today. Will
ramp up PoPs in the S from 30-40pct at sunrise to 80-90pct for
the middle of the day until late aftn.

An increase in llvl flow will bring 40-60KT easterly winds down
just a thousand or even just several hundred feet over the
highest elevations of the Laurels (mainly Somerset Co) later
this afternoon and early tonight. BUFKIT sounding for JST
suggests that a stable layer will hold on there during this
lljet passage. Without instability, it may not mix down to the
ground. In areas west of the ridges, the downsloping makes it a
little higher chc that the higher wind speeds would mix in. So,
there is a 50pct chc that there could be a gust or two over
40KT in our CWA. This isn`t high enough of a risk to post an
advy at the moment. The dayshift will have a little more data to
work with to see if we would need an advy for Somerset Co. Maxes
will hold close to 70F in most places, with the higher elevs
holding in the 60s.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Showers should remain off and on throughout the night as
moisture getting pulled into what`s left of Hurr Helene (which
will be wabbling westward into the lower OH valley). The true
tropical moisture plume will be pulling out to the east and
leave PA in a general light rainfall. There is a sliver of neg
LIs aloft per NAM and GFS. So a TSRA cannot be ruled out (20pct
chc), mainly in the central counties. The risk for any 40KT
gusts should be over by midnight as the lljet passes. Again, too
low of a prob to make a wind advy at this point. Temps only drop
5-6F in most places tonight.

Saturday, we should see the bulk of the showers/light rain lift
northward through the day, and perhaps drop southward again as
the night starts with some ridging trying to develop overhead.
Sat should be a little milder than today.

By Sunday, the heavily-modified remnants of Helene will have
combined with a deep upper low to our southwest. This upper low
will be nosing into PA on Sunday. Height falls and moisture from
the Atlantic will lead to an increase in rainfall, mainly in the
south. Sunday should be a cool day with highs only in the 60s
under thick clouds.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Complex pattern early next week. Hard to see much widespread
dry weather prior to later Wed.

There has been a lot of spread on the large scale pattern
lately.

More information below.

An upper-level low over the Ohio Valley will drift east across
the Commonwealth into the beginning of next week, keeping rain
chances around through at least Tuesday. Uncertainty begins to
increase towards the middle of the week as a northern stream
shortwave tracks near the region, bringing a cold front along
with it. The timing of this feature is a little unclear with
some ensemble members showing the front tracking through early
Wednesday morning while others show a later frontal passage.
Moisture appears to be limited ahead of the front and the best
forcing looks to remain to our north, so widespread rainfall
does not appear likely at this point.

High pressure building in behind the front will bring drier
weather and cooler temperatures for the end of the week. Highs
will generally be in the 60s with overnight lows in the 40s.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
A slow moving cold front will sag southward across Pennsylvania
this evening, then stall over the southern part of the state
late tonight into Friday. Low level moisture ahead of the front,
combined with nocturnal cooling and an upsloping easterly flow,
should yield developing IFR/LIFR cigs across the southern half
of PA tonight. By late tonight, ensemble prob charts indicate
a 60-80pct chance of IFR cigs across the southern half of the
state, with a 80-90pct along the ridgetops. Across the north,
latest guidance indicates there is the chance of IFR cigs over
the high terrain north of KIPT this evening, then the arrival of
drier air behind the front should result in improving
conditions with cigs in the high MVFR/VFR range.

Weak diurnal heating/mixing should result in modest improvement
in cigs Friday, with most locations in the MVFR category by
afternoon and possibly VFR at the Susq Valley airfields.
Moisture indirectly related to the remnants of Hurricane Helene
will start to overrun the stalled frontal boundary lying across
Southern PA Friday PM, leading to deteriorating conditions in
the form of light rain and falling cigs. Model soundings and
ensemble prob charts indicate IFR/LIFR conditions will become
likely over the Central Mtns by the evening hours. The arrival
of a core of relatively strong winds aloft could also result in
marginal LLWS criteria Friday evening, but confidence remains
below 50pct so will keep out of the forecast for now.

Outlook...

Sat-Sun...Low cigs/drizzle likely, mainly Central Mtns during
the AM.

Mon-Tue...Rain/low cigs likely, especially Central Mtns.

&&

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

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Martin/Bauco
AVIATION...Fitzgerald