Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 021937
Area Forecast Discussion
National Weather Service State College PA
237 PM EST Fri Dec 2 2016
A large and deep storm system will move slowly southeast across
northern New England late today and Saturday, keeping a prolonged
period of cool northwest flow and a gusty wind over the local
area. A ridge of high pressure will slide east across the
commonwealth for Saturday night and Sunday accompanied by fair dry
weather and light wind. A weak disturbance aloft and surface
frontal boundary will cross the region Sunday night and Monday
accompanied by some light snow across the northern half of the
state...and a period of light mixed precipitation in the south.
.NEAR TERM /THROUGH TONIGHT/...
Shallow and relatively warm strato cu deck will continue to
blanket practically all of the CWA late today and tonight. little
in the way of precip is expected across most of the northern and
western mtns of the state this afternoon and early this evening
as the mean llvl flow will remain westerly with little tap of
significant moisture off the upper Great Lakes. Significant breaks
in the cloud deck will occur across the Middle and Lower Susq
valley at times, but clouds will spread back across that area
between 20-22Z today. The Central Ridge and Valley Region will be
in between with mainly and ovc deck high-based strato cu this
afternoon and evening with nothing more than a sprinkle or flurry.
With the temps mainly in the mid 30s late this afternoon across
the NW mtns where frequent snow showers will occur, expect to see
less than an inch or snow accumulation, which will be confined to
grassy areas for the rest of the daylight hours. Elsewhere over
Central and Southeastern parts of the Forecast Area, high temps
will be in the low-mid 40s. Some locations to the east of I-83 and
south of I-81 could reach 50F during the early to mid afternoon.
A 20-30 deg veering of the wind overnight tonight following the
passage of a weak sfc/upper level trough will allow for a longer,
well-aligned fetch of chilly air across multiple glakes. Combine
this with neutral temp advection or slight cooling aloft and
increasing/moderately strong NW flow of 35-45 kts in the upper
boundary layer means that we should see increasing amounts of
NW/SE oriented, thin bands of snow showers streaming well inland
across the NW mtns and Laurel highlands, and ocnly spilling into
the Central Ridge and Valley Region.
A light accum of a coating to one inch should occur across the
Laurel Highlands overnight, while the NW mtns (specifically
Warren and Mckean counties see snowfall totals of 1-2 inches with
locally higher amounts possible north and west of the city of
Warren. Additional light snowfall Saturday morning from LES
showers could bring 18-24 hour totals to 3 or 4 inches throughout
the typical snowbelt of NW Warren County (and perhaps portions of
Mckean County). However, these amounts will be just under LES
Advisory Criteria of 3 inches/12 hours.
NW winds should even increased by 3-5 kts in sustained speeds
tonight, and with gusts some 5-10 kts night tonight as the
thermally direct subsiding left entrance region of a powerful 160
kt upper jet lifts north across the state. Gusts of 25-30 kts
possible, especially across the western high terrain and gaps just
east of ridges and along the Allegheny Front.
Min temps early Saturday will vary from the upper 20s across the
higher terrain of nrn and wrn PA, to the l-m 30s elsewhere.
.SHORT TERM /SATURDAY/...
The stacked low pressure over moves over the Canadian Maritimes.
The mean WNW boundary layer flow off the Great Lakes will be
persistent with multiple narrow bands of mainly lake effect
snow expected to spread a little more inland (developing south
across the Laurel Highlands) and last into Sat Night.
Clouds will be pesky and linger across much of the CWA right
through the day Saturday.
Max temps Saturday will be slightly colder across the north and
west, but slightly warmer than today (Friday) across the
Susquehanna River Valley. Still, these numbers are within a few
degs of normal for the first part of Dec.
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Late Sat night and Sunday brings a brief respite as high pressure
builds east across the state. Sunday evening and night, a period
of light snow is looking likely as a northern stream shortwave
races through the region with a burst of warm advection. QPF looks
to be on the order of a tenth of an inch or less, but occurring
overnight many places could see their first coating of snow of the
young season by Mon morning. Snow is more likely in the NW than
Another ridge moves through on Monday as progressive weather
pattern becomes more active. On Tues there is decent agreement in
bringing the SW US upper low up through the Ohio Valley as a
shearing out shortwave and diffuse surface low. Unless cold air
damming traps enough chilly air in the low levels to make for some
freezing rain, the precip type with this midwest system looks to
be mainly rain.
The end of the week brings some model disagreement with the
GFS/GEFS being faster than the ECMWF with the next large upper
trof and frontal system. Either way, precip looks like a good bet
around the Thu/fri period as all solutions eventually bring this
trough through. So predictability is increasing, but timing issues
remain. Best bet for precip at this point is mainly rain over the
SE as decent push of warm air lifts ahead of the system, with a
rain/snow mix further north where warm air will not infiltrate as
Behind the trough, looks like a chilly weekend in store with a
potential sharp dropoff in temps.
.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
Mid afternoon satellite loop continues to show stratocu covering
most of Central PA, associated with slow moving low pressure over
Southern Quebec. Cold air flowing over Lk Erie is producing lake
effect snow showers across Northwest Pa.
Will stick with persistence at KBFD/KJST and forecast predominantly
MVFR conditions. However, there will still be ocnl dips to IFR
with passing snow showers at KBFD.
Downsloping flow east of the mountains should result in
progressively better (high-end MVFR and low-end VFR cigs) conditions
further east. Mainly VFR at KIPT/KMDT/KLNS, with temporary dips to
MVFR cigs overnight.
Ocnl snow showers will likely drop vsbys into the 1 1/2SM-3SM
range at KBFD/KJST late today through Saturday.
The entire region will continue to see breezy conditions last
through the next 24 hours. Bukfit soundings support sustained winds
between 10-20kts across the entire region today and tonight, with
occasional gusts around 25kts (especially late tonight and early
Saturday) as mean winds in the lowest 5 kft agl veer by about 20
degrees to around 290 Deg.
Sat...SHSN with ocnl IFR vsby at KBFD/KJST, mainly in the morning.
Sun...Light snow/reduced vis possible at night, mainly NW Mtns.
Mon...No sig wx expected.
Tue...Mixed precip/low CIGs possible across the nrn mtns, with a
mdtly heavy 0.50-1.00 rainfall expected across much of Central and
LONG TERM...La Corte/RXR