Scientific Forecaster Discussion
fxus61 kctp 150118
Area forecast discussion
National Weather Service State College PA
818 PM EST Sat Dec 14 2019
cooler air will wrap through Pennsylvania tonight as low
pressure lifts north of the region. An area of low pressure
originating over the Southern Plains will track northeast into
the mid Atlantic region late Monday and early Tuesday.
Near term /until 6 am Sunday morning/...
forecast on track as cooler air slowly works its way across the
County Warning Area this evening. Drier air working its way in from the west and
temperatures even across the northwest zones have not fallen much.
This will limit accumulations across the northwest zones and higher
elevations overnight. Winds will be gusty from the west, but
not as high as previous frontal passages over the last month.
Short term /6 am Sunday morning through 6 PM Sunday/...
Sunday should be a blustery day, as region will remain under the
influence of intense storm system lifting into Quebec. Model
soundings support gusts around 30kts through much of the day.
Approach of high pressure and lowering inversion heights should
cause lake enhanced, orographic snow showers/flurries over the
western mountains to gradually diminish Sunday. Any additional
accumulation will be less than an inch. Subsidence to the Lee of
the Appalachians should result in a decent amount of sunshine
Sunday across the eastern half of the state.
Mixing down model 850 temps between -10c and -5c yields expected
Max temps from around 30f over the high terrain of western PA,
to the low 40s across the susq valley.
Long term /Sunday night through Saturday/...
the bulk of medium range guidance tracks surface low associated
with southern stream wave along the Mason Dixon line late Monday
into early Tuesday. Nbm thermal profiles support an initial
period of snow, followed by a change to rain over much of
the area. However, temperatures may remain cold enough for a
wintry mix along the northern tier even as waa ramps up Monday
night. Although the surface low is not progged to be very deep,
this system will be drawing copious Gulf of Mexico moisture
northward. All guidance currently supports potential precip
totals of around 1 inch across southern PA, the bulk of which
should fall as rain, with a stripe of light to moderate snow
accums across the northern tier.
That will be followed by below average temperatures and
generally dry weather the second half of the week, as upper
trough swings through the northeast conus.
Aviation /01z Sunday through Thursday/...
prevailing west-northwesterly flow will persist through Sunday
afternoon. Gusty surface winds at north/west airports may
produce low level wind shear through early Sunday. IFR cigs and scattered snow
showers expected at bfd and jst with gradual improvement to MVFR
by Sunday afternoon.
East of the mountains, downsloping subsidence should bring
partial clearing tonight, with a return to MVFR over the central
mountains and VFR for the southeast.
Mon...PM low cigs/wintry mix possible.
Tue...low cigs NW, improving conditions elsewhere.
Wed...restrictions likely north/west with snow showers.
Thu...no restrictions expected.