Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
706 am EST Wednesday Jan 28 2015
intense low pressure NE of Cape Cod early this morning will
continue to lift northeast toward the Canadian Maritimes today.
High pressure will build over the region during the day today...
followed by an Alberta clipper which will cross the area Thursday
and Thursday night. This system will bring a light coating...to a
few inches of snow to central and southern portions of the state
with up to several inches over the northern and western mountains.
High pressure will build into the region for late Friday into
Sat...preceded by gusty northwest winds and bitterly cold wind
chills. An area of low pressure embedded in the southern branch of
the jet stream may bring a round of accumulating snow for later
Sunday into Monday...before another surge of cold air works into
the area early next week.
Near term /until 6 PM this evening/...
sky clear across much of the region early this morning...with just some
lingering stratocu and -shsn present across the Laurel
Highlands...and thin cirrus across the susq valley.
Mesoscale ob sites show numerous locations across the northwest mountains well
below zero /at -6 to -11f/ with nearly calm air...while the ridge
tops of northern and western Penn are seeing temperatures in the single
digits above zero. Elsewhere...readings ranged from about 10-17f
with a 5-10 knots west to northwest wind.
A very light breeze will lead to a speckling of apparent temperatures as
low as -14 to -16f. However...since the coverage of these low
apparent temperatures is less than 50 percent across the northern
counties...will not be issuing a Wind Chill Advisory there.
High pressure will build east from the Ohio Valley today...providing
abundant sunshine. Vertical mixing up to just 2 kft above ground level will lead
to a northwesterly breeze of 8-13kt...with gusts into the middle and
upper teens across the region near and to the east of the susq
Despite the sun...temperatures will remain well blw seasonal
norms...in part due to fresh snow cover. Gefs mean 925temps
support highs only in the 20s. A relaxing pressure gradient will
result in a relatively light northwest wind.
Short term /6 PM this evening through 6 am Thursday/...
high pressure and associated low precipitable water air mass will drift overhead this
evening. South-sserly surface flow and anomalously strong southwesterly flow
aloft develops early Thursday in advance of a fairly potent
clipper headed our way from the western glakes region.
High cloud shield will advance east across the region this
evening...before lowering and thickening to an Alto-nimbostratus
deck early Thursday across the west.
Any light snow prior to daybreak Thursday will be limited to the
extreme northwest...and even there it will be mainly in the form of non-
Low temperatures tonight will be in the single digits to lower teens.
Long term /Thursday through Tuesday/...
a strong...several to 8 hour shot of warm air advection aloft and moderately strong
upper level divergence associated with the right entrance region
of a 300 mb jet maximum across southern Ontario will lead to periods of
light /to briefly MDT snow/ focused across the northwest half of the
state Thursday afternoon into Thursday night.
Gusty west to northwest winds and bitterly cold air with wind
chills at or below advisory criteria appear likely for Friday into
early Saturday across the central and northwest part of the state with
steady or slowly falling temperatures during the day Friday.
Saturday still not looking too bad.
For Sunday...southern stream system with decent/relatively strong
dynamics and warm air advection should spread periods of snow across the state
Sunday afternoon and night with light to moderate accums possible.
For now went with snow. However...some mix could try to work into
the area...but think system is moving too fast to get much deep
warm air into the area.
System moves out quite quickly...and should be off the coast by
late Monday morning if not sooner.
Colder air will follow for Monday night into Tuesday. Did lower
temperatures Monday night.
Aviation /12z Wednesday through Sunday/...
high pressure builds in from the west today...bringing widespread
VFR conditions. An area of IFR/MVFR ceilings will impact the SW from
kfig-kjst through middle/late morning...but these will eventually mix
out and bring VFR conditions there as well for much of the day. Northwest
winds will pick up a bit the first half of the day...with
breeziest conditions in the lower susq where sustained nwrly
winds 15 to 20 kts will develop after sunrise and persist into
Only thin high clouds poss tonight as winds become light.
Thursday...VFR to start...with restrictions spreading in from the
west starting midday.
Thursday night-early Friday...widespread IFR/MVFR in snow.
Sun...VFR to start...with late day restrictions spreading in from