Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
144 am EST Sat Nov 28 2015
a cold front will cross the area slowly tonight and Saturday...
hanging up just south of the state Saturday night. The front will
move back north early next week and is likely to bring unsettled
conditions back to the region through middle week.
Near term /until 6 am this morning/...
cold front over the northwest mountains at 06z will very slowly progress southeast
into central PA early this am. Satellite-derived precipitable water loop showing
atmospheric river of anomalous precipitable waters extending from the eastern
Pacific all the way through PA ahead of approaching cold front.
However...lg scale forcing will be relatively weak this
morning...with parent shortwave tracking well north of PA.
Thus...expect rainfall amts to be relatively light and confined
mainly to the northern mountains based on near term model output.
Temperatures will remain unseasonably mild ahead of front...which should
lie just south of kunv/kipt by 12z. Blend of latest lamp/hrrr
support mins ranging from the u30s over northern Warren/McKean
cos...to around 50f over much of central PA.
Short term /6 am this morning through 6 PM Sunday/...
the front does go slowly to the south but most guidance is now in
agreement that a wave develops along it and pushes across the
central Appalachians Sat night. While the upper support wanes
during the daylight hours on Sat...the wave should reprise the
rainfall across the southern third to half of the County Warning Area. Total quantitative precipitation forecast
through sun am should be around a tenth of an inch in the north to
a third to a half of an inch in the south...with most of that
coming Sat night. Of course there is still some uncertainty with
the quantitative precipitation forecast in the south due to recent waggling north-S of the path/track
of the weak wave. Since the surface reflection of the low pressure is
so weak and the driving force is a fast-moving thing...will top
probability of precipitation out in the 70s. As the wave passes through...it may either
bubble up some light rain into the north - or the low level
moisture could make for some dz. If it gets cold enough Sat
night...some flurries of patchy dz is possible in the northern mountains
maxes on Sat will be much above normal 50s in the south but nearly
normal l40s in the northern mountains Sat night temperatures will dip to the 20s
in the north but hold in the 40s under the clouds/rain in the southern
Long term /Sunday night through Friday/...
cold front sags to the south of PA with diminishing chances for
showers across the south. Afternoon temperatures Sunday in the 40s.
Short-wave ridge moves through Sunday night and Monday with clouds
from the next system already moving in Monday afternoon.
Precipitation moves in from the southwest Monday night. Warm air
aloft should keep most of it as rain however as it reaches
northeast toward morning hours there may be some colder areas
below 32 causing some patchy freezing rain for a brief period
Tuesday morning. Warm front moves through Tuesday as the storm
center moves northeast across the Great Lake region. The
associated cold front will then sweep east across PA on Wednesday.
Behind the front expect brisk winds and scattered showers changing
over to snow in the higher elevations and Northwest. Lake effect
snow showers in the northwest will diminish into Thursday as
another short-wave ridge pushes in Thursday and Thursday night.
Friday becomes more uncertain. Models are trending that a storm
system will move across to our south. We can expect south clouds
from this system across the southern zones and a slight chance
that precipitation would work north into the lower Susquehanna
Aviation /07z Saturday through Wednesday/...
as of midnight...isolated showers over PA. Main band SW of The
Finger lakes just ahead of cold front.
06z tafs sent.
Earlier discussion below.
A slow moving cold front over northwest PA at 03z will sag
southeast...bringing deteriorating flying conds across central PA
overnight. A moist southwesterly flow preceding the front and ascending
the northwest mountains is already producing IFR ceilings at kbfd at 03z. Model
soundings and latest lamp guidance indicate a high likelihood of
IFR/LIFR ceilings at kbfd through Sat morning.
Elsewhere...near term model data support VFR conds holding through at
least 06z...then deteriorating conds late tonight/Sat morning upon
arrival of showers with cold front.
Occasional rain and reduced ceilings should linger through Saturday...especially
for the southern terminals...as the front sags south of the Mason Dixon
line. Post-frontal low level moisture and upsloping northwest flow should
yield predominantly IFR ceilings at kjst/kbfd...with predominantly
MVFR conds elsewhere.
Sun...am rain/low ceilings possible...mainly southern PA.
Monday...no sig weather expected.
Tue-Wed...rain/low ceilings possible.
high temperature of 67 degrees in aoo yesterday...11/27...broke
the record of 65 degrees set in 1988.