Area Forecast Discussion
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FXUS61 KCTP 062034
Area Forecast Discussion
National Weather Service State College PA
334 PM EST Tue Dec 6 2016
Low pressure moving through will continue to bring a mix of
precipitation through central Pennsylvania this afternoon and
evening. A cold front will sweep southeast across the area
Thursday. A low pressure system is likely to track west of
Pennsylvania through the Great Lakes Sunday and Monday.
.NEAR TERM /THROUGH TONIGHT/...
Main focus continues to be over the high terrain of the Laurels,
where model soundings continue to show some ice accumulations
probable and latest JST ob has around a tenth of an inch so far.
Based on the low temperatures and dewpoint depressions, along with
the gusty winds, southeasterly flow, and model guidance, have
upgraded the advisory to a warning. Once the flow shifts the
precipitation should taper off, which should occur around 05Z.
As far as snow accumulations, over the higher terrain of Northern
Pa, model blended QPF is supportive of snow totals around 3 inches
by the time precip tapers off late this evening. Based on
coordination with BUF/BGM, the highest amounts should be fairly
isolated and given that it will be a rain/snow mix with mild SFC
temperatures, have lowered snow amts from WPC guidance and held
off on a winter wx advisory across Northern Pa.
Deep moisture will exit the area with passage of mid level
shortwave late this evening. However, model soundings remain
nearly saturated below 850MB, indicating the likelihood of linger
drizzle/rain and a snow mix late tonight. Superblend and high res
NAM both indicate temps creeping above freezing even across the N
Mtns late tonight.
.SHORT TERM /WEDNESDAY/...
Surface high pressure building into the region should supply a dry
Wednesday to Central Pa. However, low level moisture trapped
beneath inversion and weak mixing will likely result in stubborn
low clouds across the NW Mtns. A downsloping westerly breeze
should result in partly to mostly sunny skies east of the Mtns.
Temperatures there should respond by rising into the low-mid 40s,
while cloud cover holds readings to the mid 30s across the NW
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Broad and weak to moderate large scale lift/low to mid level warm
advection develops late Wednesday night across the mtns of Wrn PA,
and spreads across the remainder of Central PA Thursday ahead of
an approaching arctic front and beneath the thermally direct
segment of a 150kt 300mb jet moving by just to our north. Although
moisture will be lacking with this feature, the fairly impressive
large scale forcing, in conjunction with 00Z GEFS precip probs,
supports mention of SHSN (SHRASN Lower Susq) across the entire
The subsidence inversion base lifts rapidly up to 7-10 kft agl
Thursday afternoon, right through Friday night. The mean wind in
the 925-850mb layer veers from about 270 deg to 295-310 deg Friday
and Friday night creating the likelihood of a significant/heavy
Lake Effect/orographic snow event for the NW Mtns (i.e. mainly
the snowbelt of NW Warren county). Will highlight this potential
in the HWO.
Gusty NW winds could top 40 mph at times Friday.
A large area of high pressure and modified arctic airmass will
slide off the east coast Sat night and Sunday. The coldest temps
of the season so far will occur Sat night/early Sunday with lows
in the lower to mid teens across the snow covered ground of the
NW/Ncent Mtns...and upper teens to low 20s elsewhere.
00Z ECENS and NAEFS both track a surface low west of Pa through
the Grt Lks late Sunday into Monday. There could be a bit of light
snow in the WAA ahead of this feature, then milder/showery
conditions appear likely Monday before trailing cold front and
colder air arrive Mon night/Tues.
.AVIATION /16Z TUESDAY THROUGH SATURDAY/...
IFR cigs at JST and through the central mountains should continue
through 05Z before the precipitation tapers and cigs should
slightly improve. MVFR cigs will lower from south to north tonight
especially given the mixed precipitation. Confidence in ptypes is
marginal given complex and evolving thermal structure/evaporative
cooling in the boundary layer. Elevation and pcpn rates will also
be a factor. A period of LLWS is possible at BFD/JST from roughly
6/21z-7/03z. Overall, expect flying conditions to be in the sub-
VFR Tuesday night into Wednesday morning before slowly improving
after 09Z. Restrictions should lift Wednesday morning.
Wed...A.M. low cigs becoming mainly VFR.
Thu-Fri...Becoming windy with periods of snow showers. Mainly
MVFR/IFR west to MVFR/VFR east.
Sat...Decreasing winds. Low cigs/-SHSN psbl NW. VFR east.
Winter Weather Advisory until midnight EST tonight for PAZ024-