660
FXUS61 KCTP 271514
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1114 AM EDT Fri Sep 27 2024

.SYNOPSIS...
*Cloudy and humid with periods of rain and mild nights for the
 last weekend of September; rain continues to start October
*The heaviest rain is expected Sunday and Monday over south
 central PA which should be largely beneficial
*A shift toward drier/cooler weather is possible by the end of
 next week/first weekend of October

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...
A few peaks of sun along the PA/NY border early this morning;
otherwise a cloudy last Friday of September with waves of rain
and pockets of drizzle expanding from south to north across CPA
this afternoon into the evening. Updated POPs to reflect the
latest MRMS radar trends with ongoing light rain over the
southern tier lifting north of the PA Turnpike to JST/AOO/MDT
line at 15Z.

Other area to monitor will be the ridgetops along the southern
Laurel Highlands where wind gusts 35-40 mph are expected. Can`t
rule out gusts reaching advisory criteria with blended HREF/NBM
probabilities a shade over 50/50. Will insert into HWO for now
and consider matching PBZ with an advisory for later today.

Despite the extensive cloud cover, max temps in the 65-75F range
are near to even a few degrees above daily climo for this time
of year. It will also feel quite humid especially over the
southern half of the forecast area with Td 65-70F.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH SUNDAY/...
Showers should remain off and on throughout the night as
moisture getting pulled into what`s left of Hurricane Helene
(which will be wobbling 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 /15Z FRIDAY THROUGH TUESDAY/...
A slow moving cold front has become practically stalled-out and
draped east/west just south of the I-80 corridor early today.

Low level moisture ahead of the front, combined with nocturnal
cooling and an upsloping easterly flow, should help to maintain
IFR/LIFR cigs across the southern half of PA through 12-13Z today.

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.

Cigs across the north are generally MVFR with VFR Vsbys thanks to
the weak push of drier air from the NE behind the front. Conditions
should improve further today with respect to CIGS, which should lift
into the high MVFR/VFR range.

Weak diurnal heating/mixing and mixing of some drier air above 5 kft
AGL should result in modest improvement in cigs through the day
today, with most locations in the MVFR category by afternoon and
possibly VFR at the Susq Valley airfields.

Moisture steaming upslope into the CWA from the SE and indirectly
related to the remnants of Hurricane Helene will start to overrun
the aforementioned stalled-out frontal boundary lying across
Southern PA this later today and tonight, leading to deteriorating
conditions in the form of light rain and lowering cigs. CIGS will
dip back into the IFR to low MVFR range around or shortly after dusk
today across the north.

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 will likely
result in LLWS criteria late today through early today, mainly
across the Southern PA Airfields. Confidence is about 70 percent for
this to occur in the valley airfields and about 90 percent at
KJST.

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...Steinbugl
NEAR TERM...Steinbugl
SHORT TERM...Dangelo
LONG TERM...Martin/Bauco
AVIATION...Lambert/Fitzgerald