386
FXUS61 KCTP 071011
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
511 AM EST Thu Nov 7 2024

.SYNOPSIS...
A slow moving cold front will drifting southeast across the
Susquehanna Valley and South-Central Mountains of the state this
morning.

High pressure will build into the region from the Great Lakes
and become centered over the state on Saturday.

An area of low pressure at the surface and aloft will move
across the Upper Great Lakes and Southern Ontario Canada Sunday
into early Monday, dragging its southward trailing cold front
across the state Sunday night into early Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
09Z surface analysis shows a slow-moving cold front stretched
from near KBGM, southwest to KUNV and KJST. This boundary was
preceded by just a few light showers along the Mason/Dixon Line
as far east as I-81.

Expect nothing more than an additional few hundredths of an inch
of rain to the south of the PA turnpike before the mid to late
morning cfrontal passage, while skies become partly cloudy near
and to the SE of the Allegheny Front as deepening
subsidence/drying occurs via a freshening WNW wind in the wake
of the front.

The partial clearing, combined with light wind and moderately
high sfc dewpoints in the 50s, may result in patchy fog early
today. Latest SREF and NAMNest indicate the most likely
locations to experience fog early this Thursday morning will be
over the Middle Susq Valley and the ridgetops of the Laurel
Highlands.

Temps in the 50s (to lower 60s in the SE) will be unseasonably
warm to start this 7th day of November.

High pressure building in from the west will be accompanied by
much drier air. This will result in increasing sunshine across
the CWA later this morning and this afternoon.

Although we referred to the Cfropa this morning, the airmass in
its wake will be much warmer than normal, with the greatest
departures of +15 to +18F occurring over the southeast half of
the CWA (highs in the low to mid 70s).

Elsewhere, high temps today will be between 60 and 65F or
10-15F above normal.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Mostly clear skies and a light wind will blanket the region
tonight as the aforementioned area of high pressure builds
southeast across PA.

A fast-moving shortwave diving across Southern Ontario/Quebec
will push a moisture-starved cold front into into the region
Friday PM. Nothing more than a few late day cumulus over the N
Mtns are expected based on model RH timesections.

An increasing pressure gradient ahead of the front should
result in gusty west winds, which should result in fire weather
concerns due to the long dry stretch we are in. Bufkit soundings
support gusts a bit above NBM guidance in the 20-25kt range.

Forecast soundings also show relatively dry air above a weak
inversion, indicating dewpoints will likely dip a bit below NBM
guidance. Mixing down model 900mb temps of 8-9C translates to
expected max temps Friday ranging from the upper 50s over the N
Mtns, to the upper 60s across the Lower Susq Valley.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Medium range guidance supports fair and seasonable weather
Saturday associated with high pressure building across upstate
NY. Latest GEFS and EPS continue to support a good chance of
much-needed rain Sunday PM into early Monday associated with a
filling upper low tracking from the Central Plains into the Grt
Lks. A plume of +2-3SD pwat overrunning an approaching warm
front supports high POPs. However, the upper low and best large
scale forcing should pass north of PA, so expect modest rain
totals in the 0.25 to 0.40 range based on latest EPS plumes.

Fair and mild conditions currently look likely Mon PM through
Tuesday night, as upper level ridging builds toward the area
from the Midwest. The next chance of rain comes toward the end
of the long term period, as the upper flow pattern across North
America becomes more amplified. There is considerable model agreement
that a cold front will be approaching from the Midwest by Wed
PM. However, there remains plenty of uncertainty whether
moisture from the remnants of Rafael train north ahead of the
front or not. EPS plumes indicate significant rain is possible,
but there is plenty of uncertainty this far out.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
06Z/1am EST Update: The previous forecast remains mostly on
track with regards to lower ceilings moving across W PA with JST
remaining at MVFR thresholds. BFD/AOO remain at VFR at this
time, but generally expect these to deteriorate towards MVFR
based on current Nighttime Microphysics/recent RAP model
sounding trends. Low-level moisture at IPT is expected to
lessen over the next 1-2 hours, allowing for some erosion on
the low-level cloud deck and visibility improvement. Some model
guidance suggests fog formation could linger all night;
however, this seems like a lower probability (~30%) solution
compared to some clearing and potentially fog formation in the
11-13Z timeframe with an influx of low-level moisture progged by
model soundings (~50-60% confidence in this solution).

Previous Discussion Issued 817 PM EST 11/06/2024:
As a cold front moves slowly through NW PA, MVFR cigs will
continue at BFD and JST, with a trend toward IFR cigs at JST
after 02z and at BFD by 05-10z. Lower confidence in MVFR cigs at
AOO and UNV in the 03-16z time frame. One or more broken bands
of rain showers are expected with the cold front, but
significant vsby drops are not anticipated. Fog has developed at
IPT and will likely remain until drier air can move in from the
west (07-10z, or later if the sfc layer is too stable to mix).

Winds will continue to veer to become NW by Thursday, with
gusts of 15-20 kts by afternoon. The NW flow will usher in drier
air, eroding the low clouds with all TAF sites expected to be
VFR by 17-20z Thu.

Outlook...

Fri-Sun...Patchy AM valley fog possible, mainly north.
Otherwise, predominantly VFR.

Sun(late)-Mon...Widespread rain showers with restrictions
possible.

&&

.FIRE WEATHER...
Gusty west-northwest winds of 20-25kts, combined with very dry
fuels and leaf litter, will result in an elevated risk of
wildfire spread Friday afternoon, especially over the southern
half of the state, where relative humidity will dip to between
30-35 percent.

&&

.CLIMATE...
A new record high temperature of 76 degrees was set at
Williamsport on November 6th. This broke the previous record of
74 degrees set back in 2015.

A new record high temperature of 80 degrees was set at
Harrisburg on November 6th. This broke the previous record of
77 degrees set back in 1948. This was the latest 80 degree
temperature at Harrisburg on record.

Near record warmth in the low to mid 70s is expected across the
Lower Susquehanna Valley again Thursday.

&&

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

&&

$$

SYNOPSIS...Lambert/Fitzgerald
NEAR TERM...Lambert/Fitzgerald
SHORT TERM...Lambert/Fitzgerald/Bowen
LONG TERM...Fitzgerald
AVIATION...Colbert/NPB
FIRE WEATHER...Lambert/Fitzgerald
CLIMATE...Fitzgerald