561
FXUS61 KCTP 241925
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
325 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/...
Plentiful sunshine today as an upper level ridge moves in from
the west. At noon, dewpoints in the mid 40s to low 50s have
mixed down in northern PA and pleasant conditions will prevail
today areawide. A slow- moving frontal boundary is across southwest
PA, though it appears to have drifted south of the Mason-Dixon
line farther east as indicated by lower dewpoints and clear
skies there. Cumulus are prevalent in southwest PA where
dewpoints are still in the 60s and a few light showers remain.
High-resolution guidance indicates an isolated shower or storm
cannot be ruled out, but it would be confined to southern
Somerset or Bedford County most likely.

Max temperatures this afternoon will be very similar to
Thursday, ranging from the upper 70s in the northern mountains
and Laurels to middle 80s elsewhere. Would not be surprised to
see temperatures trend higher than expected today with
relatively dry air in place and ample sunshine. Scattered
cumulus clouds will develop this afternoon, but an otherwise
picture perfect day is in store. Pretty good signal for trending
dewpoints lower than expectation, ranging from the low 40s N of
I-80 to 50-55 down to the Turnpike.

Cumulus field will fall apart this evening with the loss of
daytime heating. Surface ridging over the state should ensure
fair weather overnight. Mins tonight should be in the 50s
(coolest N) except perhaps the Lower Susq where they`ll be right
around 60F. Would not be surprised to see a few spots dip into
the 40s. Could be a bit of patchy fog in the southwest where it
rained this morning, but no significant impacts expected.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Increasing clouds likely on Saturday ahead of a shortwave that
will knock the minor ridge aloft down to a more-zonal flow.
Some uncertainty in storm coverage and timing on Saturday as
shortwave helps transition weak ridging to more zonal flow
aloft. HRRR is more progressive with SHRA/TSRA in the northwest
mountains by midday, whereas 3kmNAM is slower and develops
storms later in the afternoon. When storms form, movement should
progress to the southeast and weaken with eastward extent.
Sufficient instability (1000-2000 J/kg of CAPE) will provide
enough fuel for strong to severe storms Saturday afternoon,
prompting SPC to put most of the area in a Marginal Risk.
Meanwhile, WPC highlights much of southwest/central PA in a
Marginal Risk for excessive rainfall mentioning the potential
for multiple rounds of rain to produce >1.5" in spots. HREF PMM
paints isolated totals >1" in the western mountains. Don`t think
flooding will be much of an issue Saturday, but rainfall could
be a primer for flood risk early next week.

Showers exit to the east overnight Saturday, though some
indication of lingering light showers in the east through
daybreak. Expect clearing skies and calm winds as high pressure
builds in. Mins will be 55-65F from NW to SE, likely getting
pretty close to the dewpoint. As such, expect patchy valley fog
by daybreak Sunday. 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. Isolated to scattered showers and thunderstorms
will develop Sunday afternoon mainly across the higher terrain
of 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 steady 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 /19Z FRIDAY THROUGH WEDNESDAY/...
VFR conditions are expected to prevail at all airfields across
central PA through 06Z Saturday with high (> 80%) confidence
with SKC and light winds for a majority of the period.

After 06Z Saturday, models begin to outline some deterioration
at IPT/LNS with lowered vsbys. Clear skies will promote some fog
formation with model soundings outlining low-level moisture
across the area. A light breeze keeps fog concerns less at IPT
while calm winds at LNS brings about higher probs of IFR and
below cigs at LNS. Given uncertainty on how quickly calm winds
resolve, have trended LNS`s vsbys down in the 12Z TAF package
but have not pushed them down to IFR thresholds at this time.

Outlook...

Sat-Sun...Mainly VFR, but chance of showers (mainly Sat)

Sun PM - Mon PM...Restrictions possible with periods of
SHRA/TSRA

Tue...Scattered SHRA possible.

Wed...Widespread SHRA.

&&

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

&&

$$

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