Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 271741
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
1241 PM EST Fri Jan 27 2023

.SYNOPSIS...
A series of weak shortwaves will rotate through a larger scale
upper trough over the northeast CONUS today through Sunday
bringing a few periods of light snow showers, mainly to the
Northern and Western Mountains of the state.

Afterward, a building ridge is expected off of the East Coast
early next week. A weak storm lifting out of the Miss Valley
could affect the region by the middle of next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Regional radar mosaic indicates a very slow weakening trend
to snow showers and flurry returns. Temperatures are above
freezing over the southeast so no accums or issues related to
the flurries pushing into Dauphin County are expected. Farther
west, additional coatings to less than one inch are possible
over the Laurel Highlands where visibilities are still locally
in the 3/4 to 11/2sm range. Earlier expanded the coverage of
snow shower and flurry activity to accomodate the activity
reaching the Lower Susq, which a few CAMs had hinted at
yesterday and overnight. All other aspects of going forecast
remain in good shape this morning.

     Previous discussion:
A well-defined low to mid level thermal trough (with 850-700 mb
temps of -13C to -18C) and favorable mean westerly flow optimal
orographic lift will bring a likelihood of briefly moderate to
heavy, cellular and quasi-linear snow showers this morning
across and just to the east of the Alleghenies.

SPC mesoanalysis snow squall parameter depicts several areas in
the 1-1.5 range acrs the CWA with the most favorable conditions
early today noted across the Western Mtns of PA and the Southern
and Western Poconos, where a slow moving band of snow showers
containing 20 DBZ reflectivity up to 9kft AGL was likely
reducing vsbys AOB 1/2SM over a small area along I-80 and I-81
in Columbia and Schuylkill Counties.

Look for a coating in some of the valley locations just SE of
the Allegheny Front...near and to the south and east of I-80 and
I-99 respectively. 1-2 inches of additional snow accum is likely
across the Laurel Highlands, with perhaps up to 3 inches on the
ridges tops of the Ski Country west of RT 219 in Somerset Cty.a
coating to 1 inch is possible over the Mtns NE of KIPT and the
Western Poconos where the pool of coldest air aloft will be
approaching during the late morning/early afternoon and where
favorable llvl orographic flow resumes east of the Susq Valley.

The aforementioned thermal trough slides east across the Central
Ridge and Valley Region of PA during the late morning through
mid afternoon hours, followed by temps warming 0.5-1C/hour in
the 850-700 mb layer for several hours later this afternoon.

Mixing down model 850mb temps of -10C yields expected highs
near seasonable levels Friday, ranging from the upper 20s over
the northwest mountains, to near 40F across the Lower Susq
Valley.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
Warm advection ahead of an upstream shortwave should spread
thickening clouds into the region tonight, with a bit of very
light snow possible, mainly over the northwest mountains where
orographic lift will be greatest in southwest flow. Cloud cover
and a southwest breeze should keep temps from falling much
Friday night with lows in the mid to upper 20s.

Generally fair and milder conditions appear likely Saturday, as
upper level trough begins to lift out. However, warm advection
ahead of a weak low over the midwest is likely to keep skies
mainly cloudy. It will be milder, with temps ranging from the
mid 30s in the north to the mid and upper 40s in southeastern
zones.

A slightly better organized sfc and upper level trough
(supported by a coupled jet circulation, but with limited deep
layer moisture) will move through the state Sunday. Models have
trended warmer with this system, with little to no snow accum
before a transition to light rain.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
In the big picture, an amplified eastern Pacific upper ridge
and generally depressed height pattern over most of the CONUS
will start next week. With time, the eastern Pacific upper ridge
is forecast to progress into western North America, with a
downstream trough axis gradually sharpening up over the eastern
half of the CONUS. In general, this will keep an active pattern
in place, with a storm track carved out from the south- central
U.S. up into the northeastern states.

As for the daily sensible weather, it appears that Monday into
much of Tuesday will feature either dry weather, or just spotty
light precipitation, with a surface high extending out of the
upper Midwest our main weather feature. The biggest uncertainty
surrounds the track of a southern stream wave during the mid-
week period and the footprint of its precipitation shield. For
now, we have an area of snow, or a wintry mix entering the
Commonwealth Tuesday night into Wednesday, however recent trends
have been farther south with this feature. At this early
juncture, it looks like we may get at least a brief reprieve
from precipitation later next week.

Temperatures should average close to seasonal norms for late
January/early February, with daily highs in the upper 20s and
30s for the higher terrain, and the 30s to lower 40s in the
Susquehanna Valley.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
Snow showers will diminish this afternoon across the western
terminals along with rising cigs at BFD and JST with MVFR
trending to VFR late this afternoon. Elsewhere VFR conditions
are expected this afternoon and early evening. Clouds will
increase and lower tonight as an area of low pressure passes
norht of PA. Cigs will drop back to to MVFR levels at JST and
BFD, but should remain VFR elsewhere. A couple of snow showers
will be possible at BFD and may bring brief reductions in
visibility.


Outlook...

Sat...Mostly VFR.

Sun...A chance of snow and rain showers, mainly late.

Mon into Tue...Still a chance of rain and snow showers.

Wed...Snow showers possible in the south.

&&

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

&&

$$
SYNOPSIS...Lambert/DeVoir
NEAR TERM...Lambert/DeVoir
SHORT TERM...Lambert/Colbert
LONG TERM...Jurewicz/Travis
AVIATION...Travis


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