Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
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FXUS61 KCTP 101103
Area Forecast Discussion
National Weather Service State College PA
603 AM EST Sat Dec 10 2016
Lake effect snow will continue today with total accumulations
around 2 feet across the perennial Northwest Snowbelt. A mixed
precipitation event is expected Sunday into early Monday with
snow and ice accumulation possible. The winter pattern remains
active with another opportunity for snow around midweek followed
by a shot of arctic air and frigid temperatures next
.NEAR TERM /THROUGH TONIGHT/...
Apologies for the late AFD issuance, we lost an hour due to fire
Long-duration lake effect event continues with an additional
2-4/1-3 inches across much of Warren and McKean County. Total
snow accumulations will exceed 2 feet over the snowbelt region in
northwest Warren County. HIRES models show LES bands becoming
focused more into SW NY later today into early tonight. Outside of
the lake effect area, expect a partly to mostly cloudy day with
light snow showers and flurries spilling southeast over the
Alleghenies into the Central Ridge and Valley region.
.SHORT TERM /SUNDAY THROUGH MONDAY/... Increasing warm advection
ahead of mid level wave moving into the Great Lakes should spread
light snow into western areas by early Sunday. The main surge of
WAA moisture arrives Sunday night into early Monday morning in
association with strong 50kt SSW 850mb LLJ. The models show the
warm moist air overrunning the cold airmass currently in place
which likely results in a ptype transition /snow to sleet-freezing
rain/ from south to north. This changeover is most likely to
happen in the 00-12z Monday period and impact the Monday morning
commute. Confidence in forecast snow and ice amounts is below
average given complex nature of wintry mix event and uncertainty
in the 850mb 0C line. That being said, a winter weather advisory
may be needed and will allow the dayshift to make a final
assessment. Steady to slowly rising (non-diurnal) temps early
Monday morning should continue to warm through Monday afternoon
with any lingering pcpn falling mainly in the form of rain/dz.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Scattered snow showers Monday night across the Western Mtns of PA
will diminish as a weak ridge of high pressure at the sfc slides
east from the Ohio Valley. Tuesday will begin a cool down in temps
over a several day period as progressively cold chunks of arctic
air move southeast ahead of the main, sub-500 dam Polar Vortex
that will be moving to near James Bay Canada by late Wednesday
The coldest airmass of this young winter will spread into the region
for Thursday and Friday. Temps Thursday could conceivably struggle
to get above 10F for highs across the NW mtns. The GEFS shows a
small area of -2 to -3 sigma temps at 850 mb with values around -18
West-Northwest wind gusting between 25 and 30 mph both Wednesday and
Thursday will create wind chills of 5-10 below zero during the
morning hours Thursday (mainly across the NW mtns), and only in the
single digits during the daylight hours. Skies will become mainly
clear with the wind dying off Thursday night as a 1025 mb sfc high
build east from the nation`s heartland. This will set the stage
for frigid temperatures - but several degrees above record lows.
Min temps early Friday could dip to zero to 5 below across the
fresh snow covered ground of the Laurel Highlands and NW mtns, and
will be in the single digits to teens.
Fair and dry (but very cold) weather is expected to persist Friday
night. However...a moisture-laden storm will likely impact a large
chunk of the region (beginning Friday) with snow changing to mixed
precip of from the SW.
Saturday and Sunday, clouds will thicken up quickly and
precipitation will begin shortly afterward Saturday morning. It`s
too early to give specifics on that storm w/resp that storm. 10/00Z
EC and GEFS do infer a widespread wintry (snow) precip
event...likely changing to some light sleet or fzra as the thicker
seeder/feeder cloud shield slides off to the east.
.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
Cold WNW flow pattern will continue snow showers and MVFR/IFR
conditions over the western 1/3 of the airspace. Low VFR to MVFR
cigs will prevail at the central terminals with brief MVFR vis
possible. VFR over the southeast.
Sun-Mon...Widespread MVFR/IFR in wintry mix changing to mainly
rain by Monday afternoon.
Tue...MVFR cigs and -shsn psbl wrn 1/3. VFR central/east.
Wed...Restrictions possible with next wintry system.
Lake Effect Snow Advisory until noon EST today for PAZ005.
Lake Effect Snow Warning until noon EST today for PAZ004.