Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 182214
AFDCTP

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

.SYNOPSIS...
An amplifying upper level trough will drift across Pennsylvania
through tonight, followed by a reinforcing shortwave and
associated cold front with gusty winds between 30 and 40 mph
on Wednesday.

High pressure is likely to build over the area Thursday. A
dying cold front is likely to approach from the Great Lakes late
next week, as a southern stream shortwave passes well south of
the state.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Water vapor loop at 22Z shows a deep upper level trough pushing
into PA from the Grt Lks. Modest instability ahead of it is
producing mostly light snow showers across the Alleghenies and
central mountains, while dry air and downsloping flow is
maintaining fair but chilly dry conditions across the Susq
Valley.

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 begin the evening over the NW Mtns, then
pivot south into 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/...
After the troughs overhead and at the sfc pass, the subsidence
should quell the SHSN/SQ for at least the next 18 hrs into late
Tuesday. The ridging should also push lake effect snows to our
N. A northern stream wave/Clipper moves across ONT into NY late
on Tuesday and does not bring the coldest of the air across PA
until Wed. The warm advection does nudge into PA. The
associated cold front will not arrive until the overnight. That
will likely touch off SCT SHSN, but squalls should not be very
likely without much instability. Mins tonight will be below
freezing for all. Temps on Tuesday will be very similar to
today/Monday. The warm advection and more clouds Tuesday night
will keep the mins up just a little vs tonight - in the u20s to
m30s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
The passage of the trailing cold front Wednesday should be
accompanied by scattered 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, mainly
across the N Mtns. Fair, but still cool, weather appears likely
Thursday, as the trough lifts out and surface ridging builds in
from the Grt Lks.

Medium range guidance suggests a few rain showers are possible
Friday, mainly over the N Mtns, associated with the approach of
a dying cold front. The bulk of guidance tracks a more
significant southern stream shortwave and associated area of
low pressure well south of PA next weekend. Therefore, fair and
seasonal conditions currently appear likely next Sat/Sun.

&&

.AVIATION /22Z MONDAY 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 late this afternoon and
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 late today 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-Friday...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...Lambert
NEAR TERM...Fitzgerald
SHORT TERM...Lambert
LONG TERM...Fitzgerald
AVIATION...Lambert/Bowen
CLIMATE...Steinbugl


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