754
FXUS61 KCTP 050322
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1122 PM EDT Fri Oct 4 2024

.SYNOPSIS...
* Areas of fog fade to pleasant sunshine to start to the first
  weekend of October
* Isolated strong thunderstorms possible Sunday PM across parts
  of western PA; then drying out and cooling down next week
  with frost risk

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
The shortwave to our north that provided a few showers across
Warren and McKean counties earlier this evening has moved away
from the area and the trough axis is now mostly to our east. At
the surface, northwesterly flow has developed across the
northern tier which is ushering in a drier air mass. This should
limit widespread fog development across the northwest half of
the area tonight, though patchy dense fog has developed across
the Lower Susquehanna Valley and we have issued an SPS through
08Z at which point most models suggest that drier air moving in
should lead to a decrease in fog coverage. This may need to be
reevaluated though through the night.

High pressure builds into the region tomorrow and will provide
mainly sunny skies. Ensemble mean 850mb temps in the 7-9C range
support highs ranging from the low to mid 60s over the N Mtns,
to the mid 70s in the Lower Susq Valley. We have continued to
undercut NBM dewpoints based on model soundings, which show very
dry air above a weak inversion.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Fair and seasonable weather appears likely into the first half
of Sunday before rain chances begin to increase during the
afternoon ahead of an approaching cold front. Models still show
slight timing differences with the front, but showers and
thunderstorms will be most likely during the late afternoon and
evening. Instability looks to be fairly limited ahead of the
front, with most guidance showing ~500-800 J/kg of SBCAPE, but
with 35-50 knots of 0-6 km bulk shear, some organization of
storms could be possible across the western half of Central PA.
SPC has placed this region in a marginal risk of severe weather
with isolated damaging wind gusts being the primary hazard.

Rain will quickly come to an end behind the cold front and skies
quickly clear out for most of the area as high pressure builds
in. Low temperatures Sunday night will range from the mid 40s
across the north and west, to the mid 50s in the southeast.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Enhanced northwesterly flow in the wake of the cold front will
usher in a drier airmass, thus keeping Monday mostly dry.
Cyclonic flow and neutral to falling upper level heights could
allow for a shower in the Alleghenies, but trends have been for
drier air to filter in quicker. High pressure builds into
central PA Monday and holds some influence through much of the
week, but will have to monitor the potential for a couple
reinforcing fronts through midweek as an upper low near southern
Hudson Bay rotates a couple of lobes of energy through the
Great Lakes and toward PA. Questionable as to the degree of
moisture return and associated rain chances with these at this
time.

A little more uncertainty now exists in regard to frost for next
week, beginning Tuesday night. Given the aforementioned frontal
boundaries and upper troughiness keeping more cloud cover across
northern PA, radiational cooling doesn`t now look as favorable.
Ensemble joint probabilities of winds less than 5 mph and
temperatures less than 36 degrees of 30-50% support continued
mention of frost from Tuesday night on though.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Locally dense fog has formed slightly ahead of schedule at
MDT/LNS. Otherwise, forecast remains on track although the
intrusion of drier air could bring MDT/LNS out of IFR/LIFR
thresholds between 06-08Z Saturday. There is moderate confidence
on the exact timing, so have stuck with previous forecast that
has resolved fairly well with RAP/GLAMP guidance.

Previous Discussion Issued: 759 PM EDT Fri Oct 4 2024

Lingering MVFR ceilings will remain across the Lower
Susquehanna Valley (MDT/LNS) over the next couple of hours
before further deterioration is progged by the bulk of model
guidance. At this time, model guidance hones in on the 04-06Z
timeframe for some thickening of the low-level cloud deck
towards IFR/LIFR thresholds. There is moderate confidence
(~50-60%) in these conditions resolving towards 04Z Saturday
with higher confidence on these restrictions coming to fruition
after 06Z. Ceilings will continue to remain low at MDT/LNS
through 10-12Z Saturday with enhanced low-level moisture in RAP
model soundings that is also reflected with HREF probabilities
of IFR and below conditions in this timeframe. Elsewhere, some
concern for patchy valley fog at BFD close to sunrise (10-12Z
Saturday) will bring some potential for sub-VFR flight
conditions; however, model guidance remains fairly split and
given low-level drier air compared to RAP model soundings, have
decided to keep mentions at VCFG at this time with low (~20%)
confidence at fog impacts at the airfield.

Any fog formation (N PA) and low-level clouds (SE PA) are
expected to quickly lift after 12Z with VFR conditions as high
pressure settles into the area. There is high (> 90%) confidence
in VFR conditions after 13Z Saturday through the end of the TAF
period.

Outlook...

Sun PM-Mon...Showers with CFROPA move west-to-east; isolated
strong t-storm possible over the western 1/2 of the airspace.

Tue-Wed...VFR, no sig wx.

&&

.CLIMATE...
Total precipitation for the month of September was 1.11 inches
at Williamsport (-3.65" below average) which ranks as the 11th
driest on record.

The average temperature for the month of September was 63.1
degrees at Bradford (+4.2F above average) which ranks as the
warmest September on record.

Harrisburg (MDT) consecutive days streak of measurable rain
ends at 9 with only a trace recorded yesterday 10/2. This ties
the record for longest such stretch set from April 7-15, 1893
and matched May 15-23, 1893 and July 28-August 5, 1971.

&&

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

&&

$$

SYNOPSIS...Steinbugl
NEAR TERM...Steinbugl/Bauco
SHORT TERM...Bauco
LONG TERM...Guseman/Bauco
AVIATION...NPB
CLIMATE...Steinbugl/Banghoff