905
FXUS61 KCTP 071029
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
629 AM EDT Tue May 7 2024

.SYNOPSIS...
Central PA will remain in the vicinity of an oscillating frontal
boundary through midweek, with one area of low pressure along
the front passing north of the state early Wednesday. Another,
more significant, wave of low pressure will pass south of PA
Thursday. An upper level trough will then pivot into the region
late this week into next weekend, cooling things down a bit,
back close to normals.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Fog has become dense over the Lower Susq. Have posted a FG.Y for
the next few hrs to allow for the fog to lift slowly. Sunrise
should be helping out any second, now.

Prev...
Dewpoints are dropping slowly across the central mountains, and
the southern tier has yet to see any change in airmass. The
front may be down to about Route 22, and still moving south in
no hurry. The light and variable wind this AM will become
easterly, then veer around to the south, esp over the SWrn half
of the area this afternoon. That will happen as the front turns
back around as a warm front and lifts back to the north. Clouds
across the north this AM should yield to more in the way of sun.
As the day heats up, albeit meagerly, some showers, and perhaps
one thunderstorm will pop up over wrn mtns. These won`t have
the support available to continue growing/expanding eastward.
Maxes in the low to mid 70s will be 4-9F above normals with the
bigger departures over the northern tier with more sun there
than in the S.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
Low pressure will move toward PA and wrn NY this evening,
crossing the area overnight. Numerous SHRA/TSRA are expected
with the greatest coverage and intensities over the W in the
warm sector where the LLJet peaks in the evening and early
night. Intense/near-severe storms shouldn`t get much farther
east than BFD-UNV-AOO. SPC has placed the SWrn corner of the CWA
into the MRGL risk for svr wx as a cold front plows thru
overnight.

Tonight should be very warm for early May due to the clouds and
mild southerly flow before the cold front passes later at night.
Mins in the L60s will cover most of the CWA.

Model guidance tracks the weak surface low north of PA Wednesday,
with a weak trailing cold front coming through during the morning
hours. Any morning showers should give way to increasing sunshine,
as drier air works in behind the front. Model 850mb temps near
15C support highs ranging from the mid and upper 70s over the N
Mtns, to the low and mid 80s in the valleys of Central/Southern
PA.

Unsettled weather will return Thursday, as an upstream trough
approaches from the Grt Lks. Latest guidance tracks the associated
surface low south of PA, resulting in a rainy/cool Thursday, with
elevated convection and a marginal risk of severe wx along the
southern tier counties. Will likely be undercutting NBM temp
guidance Thursday if current model trends hold. Raw operational
model surface temps struggle to reach 60F over parts of the
area Thursday. Latest ensemble plumes indicate most likely rain
totals Thursday of around a half inch.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
A notable trend toward cooler conditions for late this week
through the coming weekend as a broad trough develops over the
Glakes and Eastern U.S. with several smaller scale shortwaves
moving southeast within the northern branch of the upper jet.

The surface low and deepest moisture is progged to shift east
of the area Thursday night. However, falling heights ahead of
the positive tilt upper trough (and cold 700 mb temps falling to
around -4C) will likely support scattered-numerous, mainly
diurnal showers Friday through Sunday. A low-topped tsra cannot
be ruled out Friday afternoon/early evening.

GEFS mean 850 mb temps slip to between +2 and +4C (or about -1
sigma) Friday night through Saturday, before rebounding a few
deg C Sunday into Monday. Mean 925 mb temps of just 8-10C later
Friday through Sat morning will likely top even cooler LLVL air
under cloudy conditions.

This cool airmass (with Canadian origin and trajectory over
Lake Erie waters still in the upper 40s to around 50F) will
combine with numerous late morning through early evening showers
across at least the Central and Northern part of the CWA Friday
to likely yield the coolest day we`ll see til this Autumn with
high temps staying in the U40s in some spots across the Northern
Mtns. Highs in the mid 50s to mid 60s will be common heading
southeast from the Allegheny Front.

Temps will still be 2-5 deg F below normal over the upcoming
weekend with mins at night near to a few deg F above normal due
to varying amounts of clouds and at least a light breeze, which
should limit any potential for frost to the patchy variety and
confine it to the Northern Mountains Sat, Sun and Mon mornings.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Ample low level moisture trapped beneath a surface inversion
will promote the development of fog across south central PA
into the early Tuesday morning hours. LIFR vsbys are possible,
especially at LNS and AOO. Farther north, drier air will be
prohibitive of widespread fog, but patchy valley fog remains
possible.

After morning fog lifts, most or all of central PA will see VFR
conds by Tue afternoon. Isolated -SHRA will be possible during
the day. A warm front will lift northeast across western and
central PA Tuesday afternoon and night, leading to a trend
toward increasing areal coverage of showers and thunderstorms
and a higher frequency of MVFR and brief IFR conditions,
especially after 00z Wed.


Outlook...

Tue...AM low cigs/showers possible southern tier of PA.
Scattered evening tsra impacts possible W Mtns.

Wed...AM low cigs/tsra possible.

Thu...Periods of rain/low cigs likely. Scattered afternoon
TSRA.

Fri and Sat...Showers with periods of low cigs possible.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM EDT this morning for PAZ057-059-
065-066.

&&

$$

SYNOPSIS...Dangelo
NEAR TERM...Dangelo
SHORT TERM...Dangelo
LONG TERM...Lambert/Fitzgerald
AVIATION...Gartner/Colbert