413
FXUS61 KCTP 260538
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
138 AM EDT Wed Jun 26 2024

.SYNOPSIS...
A cold front will push southeast across the region Wednesday
night, followed by high pressure building in Thursday and
Friday. A relatively zonal flow will remain in place through
early next week, with a cold front passage either late Saturday
or early Sunday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Late evening water vapor loop shows a potent shortwave tracking
well north of PA through the St Lawrence Valley. Satellite loop
at 03Z shows cumulus with decent vertical development along the
trailing low level jet from Northwest PA through the southern
tier of NY state. Warm advection along this feature could
potentially produce a shower/tsra across the N Mtns late this
evening. Otherwise, tonight looks quiet with varying amounts of
mid and high level cloudiness overspreading the state ahead of
an upstream trough over the Plains.

An active southwest breeze will draw steadily rising dewpoints
into the region tonight, resulting in much warmer conditions
than last night. See no reason to deviate from NBM mintemp,
which range from the mid 60s over the NW Mtns, to the low 70s in
the Lower Susq Valley.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/...
Diurnal heating of an increasingly moist/unstable airmass,
combined with falling heights ahead of the upstream trough, will
result in developing convection during Wed afternoon. A ribbon
of relatively strong mid level winds of 40-50kts, combined with
progged moderate instability across Central and Southern PA,
suggests organized convection and locally severe weather can be
expected across this part of the state Wed PM. Some of the
latest model guidance suggests an eastward-moving MCV could
result in a batch of strong-severe convection across Southern PA
in the 16Z-21Z time-frame, with diminished potential in the
rain-cooled air behind it. However, wouldn`t place too much
weight on this right now, as the strongest shear should be in
the late afternoon to early evening timeframe. Some of the 12Z
HREF members indicate UH values >150 across Southern PA in the
early evening, which is supportive of supercells.

Latest ensemble plumes indicates most likely aerial average
rainfall Wed PM will be around a half inch. However, isolated
amounts around 2 inches appear likely based on the latest HREF
and a combination of moderate instability and +1-2SD pwats.

Thicker clouds will likely cap temps to the upper 70s across the
NW Mtns Wed, while a decent amount of sun is anticipated across
the southeast counties based on model RH profiles. 850mb temps
support highs as warm as the low 90s across the Lower Susq
Valley. The combination of heat and humidity should result in
heat indices peaking in the mid 90s in that part of the state.

Dwindling convection from northwest to southeast is anticipated
Wed night, as the upper trough and associated cold front work
through. Large scale subsidence and the arrival of much drier
air behind the exiting cold front should then result in fair
and seasonable conditions Thursday. Surface high pressure
building over the region should result in fair and cool weather
Thu night. Fair and slightly warmer conditions are likely
Friday, as low pwats persist over PA and a return southerly flow
develops as the surface high passes off the coast.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
Latest medium range guidance is showing an unusual lack of
spread among its members, all of which track a surface low
north of PA Saturday, with a trailing cold front coming through
Sat night into early Sunday. The lack of spread with regards to
timing of the front, combined with progged GEFS pwats of
+2-3SD, supports an increasing confidence in showers/tsra
Saturday. A leading warm front could produce showers/tsra as
early as Friday night and a slowing cold front could cause
convection to linger into Sunday, mainly over the southeast
counties. However, ensemble plumes indicate the most widespread
convection should occur Sat afternoon and evening.

There is some potential for severe wx Saturday PM, as decent
mid level flow overspreads an increasingly moist warm sector.
Ensemble plumes currently indicate moderate capes in the 1000
J/kg range and model 0-6km shear is in the 35-40kt range.
If the cold front slows enough, severe wx would also be possible
across the eastern edge of the forecast area Sunday PM.

Latest EPS and GEFS both support fair weather with near to
slightly below normal temps and low humidity early next week
associated with high pressure building east from the Grt Lks.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are being observed across all of Central PA as of
05Z, but all guidance suggests that MVFR ceilings will develop
across the northwest by 09Z. These low clouds should dissipate
by mid morning and a period of VFR is expected area-wide through
at least the early afternoon.

Uncertainty begins to increase throughout the afternoon as there
are still questions about the timing of showers and
thunderstorms moving in ahead of a cold front. Showers are
likely to begin kicking up around 18Z in western PA before
overspreading to the east and strengthening through the
afternoon. A few of these storms could be strong to severe with
any impacted TAF site likely to see high wind gusts and briefly
lowered visibility. The best chance for strong storms will be
between 18Z Wednesday and 03Z Thursday. Have added broad periods
of VCTS at each TAF site, but this timing will have to be
refined with further forecast updates.

As the showers and thunderstorms exit to the east during the
late evening, guidance indicates the potential for low clouds to
stick around across a large portion of the area. The HREF shows
the highest probabilities of IFR ceilings (50-60%) at BFD and
JST, with lower probabilities of MVFR ceilings at all other
sites except MDT and LNS.

Outlook...

Thu-Fri...Generally VFR.

Sat-Sun...Thunderstorm impacts possible.

&&

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

&&

$$

SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Fitzgerald
AVIATION...Bauco/Bowen