833
FXUS61 KCTP 180755
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
355 AM EDT Wed Sep 18 2024

.SYNOPSIS...
A cut off upper low and weak surface reflection spinning over
the Southern Appalachians this morning will drift slowly to the
Northeast today before moving off the Mid Atlantic Coast
Thursday into Friday.

A ridge of high pressure at the surface and aloft will build
East from the Ohio Valley for the upcoming weekend with
generally dry conditions and daytime temperatures averaging
several degrees above normal in most places.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
MRMS and surface obs early this morning showed a few bands of
light rain pushing NWWD across the CWA and dissipating as they
approached the deeper/dry air in the lowest 7-8 kft AGL near
and to the north of Interstate 80.

We`re seeing a milder start compared to recent days with
daybreak temps ranging from the low and mid 50s over the
northern tier, to the low and mid 60s in the Lower Susq Valley.

Another few rounds of rain are expected later this morning and
this afternoon over the southern third of the state, where 2-3
tenths of an inch are possible by dusk. Locally higher amounts
near 0.50 of an inch are possible over the southern tier
counties, where some models indicate a bit of elevated
instability and the potential of a deeper warm cloud layer
and heavier showers in the 12-18Z time frame.

Elsewhere across Central and Northern PA, rainfall amounts will
be minimal, but widespread and generally thick mid level clouds
will persist with a light East to ENE breeze.

Afternoon highs today will be coolest (low to mid 60s) across
the Laurel Highlands and mainly between 70-75 degrees over the
remainder of the CWA.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/...
The weak surface low off of the NC coast is progged to drift
northeast and out to sea tonight through the week`s end.

This will cause the low level flow to gradually back from the
ESE to the Northeast, allowing drier air to advect into the
much of the CWA late today and tonight.

An increasingly northerly flow should dry things out Thursday
into Friday. However, a few bands of enhanced mid-level FGEN
forcing just to the NW of the 1008 mb sfc low east of KACY will
help to focus the best chc for rain near and to the SE of the
I-81 corridor later tonight through Thursday night where an
additional few tenths of rain are expected.

Elsewhere, partial clearing of the mid and high cloud layer is
expected with just a few sprinkles or a stray brief shower
possible. Model RH profiles support an increasing amounts of
sunshine Thursday into Friday across much of Central and NW PA.
GEFS 850mb and surface temps indicate a return to above normal
afternoon readings.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Higher confidence in dry wx/no rainfall particularly early in
the period (through the upcoming weekend) thanks to deep layer
ridge pattern at the sfc and aloft. While model variability
remains elevated into next week, the ensemble means generally
favor weak upper troughing centered around the Great Lakes which
will support a marginal increase in rainfall/shower potential
along/ahead of an approaching front by next Monday or Tuesday.
Forecast max temps 75-80F peak +5-10F above mid/late September
climo to start the weekend and trend modestly cooler to 65-75F
(near the historical average) into early next week.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
MVFR ceilings across the Laurels (JST/AOO) could show slight
hints of improvement over the next couple of hours through 09Z
with HREF probabilities and GLAMP guidance both suggesting
conditions resolving to low-end VFR near 08Z at AOO. Improvement
will be short-lived; however, as ceilings are expected to tank
towards IFR thresholds closer to sunrise (10-12Z) and continue
through at least 16Z at AOO/18Z at JST. There is some
uncertainty with regards there lower ceilings, so have these in
the 06Z TAF package with moderate (~40-50%) confidence. MVFR
ceilings are also expected to begin making way into MDT/LNS
closer to sunrise, with the most reasonable timing near 10Z,
although could realistically see these restrictions pushed back
closer to the 11/12Z timeframe as guidance continues to slow
low-level clouds (~1500ft AGL) into the LSV. Scattered -SHRA
will also be possible mainly at JST/AOO/UNV, although have
limited mentions as the bulk of shower activity has moved west
of these airfields at this time.

Recent GLAMP guidance and HREF probabilities continue to go
heavy on visibilities ~1/2SM at BFD in the overnight period, and
generally could see these coming to fruition given SKC/00000kt
conditions over multiple hours, thus have offered up ~2hrs of
increased restrictions in the 10-12Z timeframe. If ANY cloud
cover gets into BFD over the next couple of hours, this will
likely limit fog potential in the timeframe and BFD could escape
with an hour/two with MVFR thresholds (10-12Z) or, even more
likely, VFR prevailing throughout the overnight period. If fog
does manage to develop, restrictions will be quick to resolve by
13Z with VFR prevailing throughout the daytime hours.

After sunrise, improvement looks unlikely through 17Z at all
airfields (minus BFD/IPT, who outside of the aforementioned fog
restrictions at BFD will remain VFR overnight). Slow improvement
is progged by the bulk of model guidance, with MDT/LNS first to
resolve in the 16Z-17Z timeframe and JST/AOO resolving closer
to 00Z Thursday as low ceilings slowly scatter out towards VFR.

Outlook...

Thu...MVFR cigs possible in the southern and eastern portions of
the airspace.

Fri-Sun...Valley fog in the morning; otherwise VFR/no sig wx.

&&

.CLIMATE...
The first day of Autumn 2024 (Fall Equinox) begins at 8:44 am
EDT on September 22nd.

&&

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

&&

$$

SYNOPSIS...Lambert
NEAR TERM...Lambert
SHORT TERM...Lambert
LONG TERM...Fitzgerald/Steinbugl
AVIATION...NPB
CLIMATE...NPB