-- Discussion containing changed information from previous version are highlighted. --
262
FXUS61 KCTP 242344
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
744 PM EDT Fri May 24 2024

.SYNOPSIS...
*Picture perfect Friday into Saturday with warm temps &
 comfortable humidity.
*Scattered showers and thunderstorms Saturday afternoon
 preclude patchy fog overnight.
*Increasing humidity and cloud cover for Memorial Day with
 scattered to numerous showers and thunderstorms ushering in
 another unsettled week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY 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 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 SATURDAY 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.

Deepening surface low moves into the Great Lakes Sunday night
into Monday, bringing anomalous moisture and numerous showers
for Memorial Day. MRGL risk of Excessive Rainfall Sunday night
across the southwest highlights areas where rainfall amounts
will exceed 0.5" through daybreak. Risk shifts east across more
of the region on Monday. As cold front swings through Monday
afternoon and evening, convective rains may create an elevated
risk of flash flooding across eastern PA. Details will come into
focus over the weekend. Regardless of exact storm
track/rainfall amounts, scattered to numerous showers and
thunderstorms may dampen outdoor Memorial Day plans across much
of Pennsylvania and the Northeast US.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Medium range guidance shows a longwave trough setting up over
the eastern US and persist through much of the upcoming week,
with several shortwave troughs rotating through the base of the
trough. Expect a downward turn in temperatures with 850 mb temps
in the single digits only supporting highs in the 60s to low
70s by Wed-Thu. Given the low level instability beneath the cold
pool aloft, we have moderate confidence in scattered diurnal
showers and isolated thundershowers Tue-Wed, with the highest
PoPs in NW zones (closer to the upper low). Models diverge in
timing the departure of the trough late in the week. However, a
trend toward drier/warmer conditions looks likely.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
Widespread VFR conds will continue through much of the
overnight, as any lingering cu dissipate and winds become light
and variable.

Model guidance has backed off a bit on the patchy fog during
the pre-dawn hours. However, there are still some hints that a
bit of valley fog may try to form. Therefore, have kept a hint
of it in the TAFs for LNS and IPT.

Any fog that does form will quickly dissipate after sunrise on
Saturday. Predominantly VFR conds are expected into the early
afternoon, before scattered showers and thunderstorms develop
from west to east as the afternoon and evening progress.

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...Banghoff
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/Banghoff
LONG TERM...Fitzgerald/Gartner
AVIATION...Evanego