Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 190312
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1112 PM EDT Mon Mar 18 2024

.SYNOPSIS...
An amplifying upper level trough will drift across Pennsylvania
tonight, followed by a reinforcing shortwave and associated
cold front Wednesday. High pressure is likely to build over the
area Thursday. A weak northern stream shortwave is likely to
affect the area late Friday, as a more significant southern
stream shortwave and associated surface low passes south of the
state.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Water vapor loop at 03Z shows a deep upper level trough pushing
over Central PA. Large scale subsidence behind the exiting
trough should result in breaking clouds east of the mountains
tonight, while lake-enhanced orographic snow showers persist
across the Allegheny Plateau. Near term model guidance indicates
the plume of best lake moisture will shift from the NW Mtns this
evening to the Laurel Highlands late tonight. Progged inversion
heights are fairly low and the airmass remains dry outside of
lake bands, so overnight accumulations will be light. Latest
ensemble mean qpf supports overnight accums ranging from a
dusting over most of the Alleghenies, to around an inch over the
Laurel Highlands.

A well mixed boundary layer and only weak cold advection suggest
temperatures will fall slowly tonight, with daybreak readings
ranging from the mid 20s over the higher terrain of the
Alleghenies, to the low 30s in the Lower Susq Valley.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Latest guidance continues to track a clipper across the Northern
Grt Lks Tuesday. Backing flow ahead of this feature should
result in a break in the lake effect activity early Tuesday.
However, warm advection along the attendant low level jet is
likely to support some light snow across primarily the N Mtns
Tuesday. Latest ensemble mean qpf indicates accumulations of
less than an inch are likely. Temperatures will edge up a bit
Tuesday under warm advection regime, but plenty of cloud cover
should still result in max temps several degrees below average,
ranging from the 30s over the N Mtns, to the low and mid 40s in
the southern valleys.

The best isentropic lift shifts north of the border Tuesday
night. However, residual low level moisture ascending the
Allegheny Plateau should result in a few lingering snow showers
overnight in that part of the state, with clearing skies
expected downwind (east) of the mountains.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The passage of the trailing cold front Wednesday should be
accompanied by scattered rain/snow showers, a few of which
could survive into the Susq Valley, due to strong forcing ahead
of the upper level shortwave. Steep lower tropospheric lapse
rates indicate the potential of some heavier snow squalls
across the N Mtns. Deep cold advection and passage of a strong
isallobaric couplet signal a period of gusty northwest winds
behind the cold front late Tuesday. Latest Bufkit soundings
support gusts in the 30-40mph range late Tuesday into Tue
evening. Fair, but still cool, weather appears likely Thursday,
as the trough lifts out and surface ridging builds in from the
Grt Lks. Thursday night looks quite cold, as the surface high
settles over the state.

Medium range guidance suggests a period of light precipitation
is likely Friday PM associated with warm advection ahead of a
weak northern stream shortwave. Thermal profiles point to mainly
rain, but the N Mtns could be cold enough for a light snow
accumulation. Most guidance keeps a more significant southern
stream shortwave well south of the area. However, there remains
a small chance of phasing of two branches of the jet, resulting
a heavier rainfall across Eastern PA Friday night into Sat.

Fair and cool weather looks likely the second half of next
weekend, as upper troughing exits the east coast and high
pressure builds in from the Grt Lks. Rising heights noted in the
model guidance early next week, but a cold air damming
signature with strong high pressure over the Canadian Maritimes
suggests the warmup will be tempered.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Mainly VFR will continue into Tuesday across much of the
central and SE PA airspace under varying amounts of stratocu
based AOA 3500 ft AGL.

There will be occasional to persistent MVFR across PA`s
northern and western mtn airfields tonight and even some brief
periods of MVFR Cigs at KUNV and KAOO in -SHSN this into this
evening.

West-northwest winds will be moderately gusty this evening and
tonight for all TAF sites.

A dual or multi-layered cloud shield (mainly VFR) will spread
across the region Tuesday as the low level flow backs a bit more
to the west-southwest, helping to confine most of the snow
showers across the far NW zones, with generally mostly cloudy
skies and breezy and dry conditions elsewhere.


Outlook...

Tuesday-Saturday...Periodic snow showers and reductions,
primarily across the higher terrain of northern and western PA.
This will be enhanced by reinforcing shots of unseasonably cold
air and gusty W/NW winds. West to northwest wind gusts could
peak in the 35 to 40 mph range on Wednesday.

&&

.CLIMATE...
Astronomical Spring (vernal equinox) begins on Tuesday March 19
at 11:06 PM EDT.

&&

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

&&

$$

SYNOPSIS...Fitzgerald
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald
LONG TERM...Fitzgerald
AVIATION...Lambert/Gartner
CLIMATE...Steinbugl


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