541
FXUS61 KCTP 162021
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
421 PM EDT Mon Sep 16 2024

.SYNOPSIS...
A ridge of high pressure at the surface and aloft will remain
over PA today. An area of low pressure off of the South
Carolina coast will lift north into Virginia by the middle of
the week, before tracking east and off the coast by late week.
An upper level ridge over the Great Lakes is likely to build
into Pennsylvania by next weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Upper level ridging extending from the Grt Lks to Southern New
England will sustain fair weather across PA today. Warm
advection aloft/upper level diffluence ahead of a low pressure
system over the NC/SC coastline will spread a thin shield of
cirrus north across PA today. Dewpoints have dropped into the
40s and even the 30s down into the Laurels as a batch of very
dry air moved in with a wedge of subsidence associated with the
high pressure system to our northeast.

Valley fog will be possible again tonight, mainly in north
central PA. Farther south, increased moisture and thicker cirrus
aloft will inhibit radiative cooling enough to make fog less
likely. For much of the Lower Susq valley, temps tonight are
progged to be about 5 deg warmer than last, whereas 24 hr temp
change in the northern tier is expected to be closer to 0.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Whether or not Potential Tropical Cyclone Eight organizes into
a named system, the disturbance will track northwest to near
Charlotte NC by late Tuesday. The bulk of latest guidance
indicates the associated easterly low level jet and plume of
Atlantic moisture linked to this system will weaken quickly as
the disturbance moves north. However, it will come close enough
to support a slight chance of showers over the southern tier
counties late Tuesday. Any rainfall that reaches Southern PA
Tuesday should be very light.

Thickening cloud cover and an upsloping easterly flow should
hold temperatures down Tuesday across the Laurel Highlands,
where readings will likely not get out of the 60s. Elsewhere,
model RH profiles support filtered sunshine through a veil of
cirrus, with the brightest skies near the NY border.

The best chance of showers across Central PA appears to come
Wednesday, as the remnant low makes its closest pass to PA
before shifting off of the East Coast late in the week. The
bulk of recent guidance keeps the easterly low level jet and
associated highest pwats just south of the Mason Dixon Line.

The combination of increased moisture and large scale forcing
ahead of the upper low currently targets areas just south of PA
for locally heavy rain. Most likely rainfall by late Wed based
on ensemble output ranges from <0.1 inch over Northern PA to
around 0.5 inches over the southern tier. Recent dryness
suggests the threat of flooding is low, even if a northward
shift in the models brings the heavier rain into Southern PA.

A 20-30 pct chance for rain continues into Thu, as various small
low pressure centers attempt to take shape off the Mid Atl
coast.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
An upper level low over the region will keep clouds and showers
around through most of the extended period. The best timing for
showers remains unclear as this will be dependent upon the
timing of multiple surface lows that will track near Central PA.
Uncertainty begins to increase towards the weekend as there is
quite a bit of spread in the guidance with respect to a building
ridge to our west and how quick it pushes eastward. Ensembles
suggest that the upper low will be slower to be replaced by
ridging than had been shown over the past few days which will
keep the chance for a few showers around through the weekend.
Temperatures will generally be on a slight downward trend
through the period with highs in the upper 60s and low 70s by
Sunday and Monday.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
Late afternoon update.

Looking at just some high clouds across the area late this
aft. Adjusted winds a bit in the TAF package.

Earlier discussion below.

VFR conditions prevail across central Pennsylvania with high
(~90-100%) confidence that the main concern throughout the day
will be gusts reaching upwards of 10-15kts across the Laurel
Highlands (AOO/JST) this afternoon and early evening.

Increasing mid-to-high level clouds are expected to enter
southern Pennsylvania by evening and gradually expand northward
with some thickening of the cloud deck as it progresses.

The main concern for restrictions come near and after 06Z
Tuesday as lower ceilings begin working into southern
Pennsylvania. Some uncertainty on ceiling heights/timing bring
about lower (~40%) confidence in the TAF throughout this period;
however, expect LNS/MDT to dip towards MVFR thresholds
generally in the 06-08Z timeframe and into the end of the TAF
period with concerns for onset of IFR ceilings towards 09-11Z
Tuesday timeframe.

At this time, MVFR ceilings seem most likely at MDT/LNS
(mentioned above) along with AOO/JST. There is lower confidence
further north for UNV/IPT.

Outlook...

Wed...SHRA w/ Isolated PM TSRA, highest chances across SE PA.

Thu-Fri...Lingering showers possible, mainly across the east
and south.

Sat...Mainly dry conditions.

&&

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

&&

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

&&

$$

SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald/Colbert
SHORT TERM...Fitzgerald/Colbert
LONG TERM...Dangelo/Bauco
AVIATION...Martin/NPB/Tyburski
CLIMATE...NPB