-- Discussion containing changed information from previous version are highlighted. --
717
FXUS61 KCTP 250553
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
153 AM EDT Sat May 25 2024

.SYNOPSIS...
A shortwave passing north of the region will push a weak cold
front through the state Saturday night. Low pressure will then
track west of Pennsylvania Sunday night into Memorial Day, with
the trailing cold/occluded front coming through Monday evening.
An upper level trough will build into the region for the
remaining portion of next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Surface ridging building into the region from the Grt Lks will
supply Central PA with fair weather overnight. Upstream
satellite imagery indicates a bit of thin cirrus will drift into
the area, but mostly clear sky wording should suffice.

Conditions will be favorable for efficient radiational cooling,
especially over the N Mtns, where pwat anomalies are greatest.
Thus, have blended the cooler MAV min temps with those of the
NBM across the northern counties. Expect daybreak readings to
range from the upper 40s in the coolest northern valleys, to
around 60F across the Lower Susq Valley, where higher dewpoints
remain in the vicinity of a remnant frontal boundary. Will
continue to mention patchy late night valley fog in the valleys
of Southern PA, where low level moisture is highest.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
The focus Saturday will be on a shortwave lifting across the
Eastern Grt Lks. The bulk of the large scale forcing is progged
to pass well north of the area and no height falls are progged
over PA. However, diurnal heating, combined with surging
moisture ahead of a weak cold front, will likely result in a
shower/tsra in many locations Saturday PM. The latest HREF
indicates convection will likely develop over the NW Mtns early
Sat afternoon, then spread into the central part of the state by
early evening.

In general, weak deep layer shear should limit storm
organization. However, progged capes in the 1000-1500 J/kg range
could support an isolated strong to severe storm. Somewhat more
favorable shear is noted over the extreme northwest part of the
forecast area, where HREF updraft helicity values support
better storm organization and the potential of a brief
supercell. Ensemble plumes indicate areal average rainfall
Saturday afternoon/evening will be fairly light (<0.25 inches).
However, the 12Z HREF supports isolated amounts up to 1.5 inches
from any heavier storms, mainly across Warren County.

A dwindling band of convection should push eastward across the
forecast area late Sat evening associated with the passage of
the weak cold front. Clearing skies, light wind and wet ground
in places should set the stage for patchy late night valley fog.

Model guidance supports fair and warm weather Sunday, as upper
level ridging builds over PA ahead of an upstream trough and a
weak surface high builds in from the Great Lakes. However,
diurnally-driven convection may develop Sunday afternoon across
Southern PA, where modest capes are noted in the model
guidance. GEFS 2m temp anomalies are close to 10 degrees above
normal Sunday afternoon, translating to highs ranging from the
upper 70s in the Endless Mountains to the mid 80s through the
Susquehanna Valley.

All guidance tracks a seasonably strong surface low northeast
across the Grt Lks Sunday night into Monday, with a trailing
cold/occluded front likely coming through Central PA Monday
night. Falling heights/upper level diffluence ahead of the
associated upper trough, combined with surging pwats along the
attendant low level jet, should result in numerous showers/tsra
late Sunday night through Memorial Day. Ensemble median rainfall
during this time period is 0.50-1.00 inches, representing the
most likely areal averages. However, embedded tsra should
result in locally heavier amounts and potentially an isolated
flood threat.

Current guidance indicates the best chance of severe weather
will be in the warm sector across Western PA Mon PM. The latest
NAM and GEFS hint at a triple point low passing south of Central
PA, with lingering low clouds/southeast flow north of this
feature keeping Central PA cooler and less prone to severe wx.
However, we`re still several days out and the mid level flow and
deep layer shear looks fairly impressive. EPS CAPE plumes over
Central PA Mon PM are widely dispersed, ranging from <300 J/kg
to almost 2000 J/kg if the warm front lifts east of the
Appalachians.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Medium range guidance all points to a period of cool weather
later next week, as a deep upper level trough pivots southeast
from the Grt Lks. The cold temps aloft should support a daily
chance of diurnally-driven showers, with the highest POPs across
the elevated heat source of the Allegheny Plateau. The best
chance of showers and isolated tsra overall should come with
the passage of a strong shortwave Wednesday. Both the GEFS and
EPS signal drier and warmer weather late next week, as the upper
trough shifts east of PA.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Widespread VFR conds are expected to continue with moderate-to-
high confidence (60-70%). Recent guidance takes out BR/FG
mentions at IPT/LNS, likely due to slightly less low-level
moisture, as seen on recent dewpoint depressions across the
region. Clear skies with calm/light winds will allow for some
fog potential across SW PA where there is slightly more moisture,
but generally expect these instances to be localized and away
from all terminals.

Any fog that does form will quickly dissipate after 12Z
Saturday with predominantly VFR conds throughout the early
afternoon hours. As the afternoon progresses, scattered showers
and thunderstorms are expected to develop and could cause brief
restrictions. Some uncertainty remains with regards to
coverage, but have began to time out any SHRA/TSRA mentions in
the 06Z TAF package. Conds are outlined to stay above MVFR
thresholds; however, localized heavier showers/storms could
bring about restrictions. After rainfall ends late Saturday
evening and into Monday morning, guidance hints towards
restrictions at BFD after 04Z Sunday and believe this is
plausible at this time with saturated grounds, light winds, and
some potential for breaks in clouds.

Outlook...

Sun...Patchy AM fog, otherwise predominantly VFR outside of a
stray aftn shower.

Sun night-Mon...Restrictions possible with SHRA/TSRA
developing.

Tue-Wed...Scattered SHRA possible.
-- End Changed Discussion --

&&

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

&&

$$

SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Banghoff
LONG TERM...Fitzgerald
AVIATION...Evanego/NPB