Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1054 PM EST sun Nov 29 2015
cooler air is sliding in from the northeast as high pressure
builds into the region tonight. An upper low over the plains
states will then slide across the Great Lakes through midweek. A
period of rain will result from Monday night into Wednesday.
Temperatures will be seasonably cool all week long.
Near term /until 6 am Monday morning/...
extensive middle and high clouds have overspread most of central and
southern PA this evening as shortwave ridging and milder flow
aloft moves in from the Ohio Valley. Low level cold air associated
with surface high over Quebec continues to build southward into the
region...with a broken stratus deck dropping southward through New York
state. Thus the overnight will be mostly cloudy to cloudy across
central PA. Cad east of the alleghenies and enhanced upslope into
the Laurel Highlands may produce some stratus there late tonight.
Otherwise it will be quiet tonight. Mins will be near to slightly
below normal...ranging from the lower 20s north to the lower 30s
Short term /6 am Monday morning through Monday night/...
on Monday...the 925-850mb winds turn to the south/east. This will
bring moisture back into the SC mountains before sunset on Monday. The
moisture will get thicker through the night as it spreads north/west
upslope. There will probably be some dz...and the temperatures will be
marginally cold enough for it to freeze Monday night if sufficiently
cold air can seep into the south /an unlikely scenario/. Maxes
Monday will be only 40-45f. With the increasing clouds...the diurnal
change from Monday to Monday night will be little more than 5-8f.
The upper low over the plains will deepen and slide to the east
into the upper Great Lakes. Deep southwesterly flow will bring
rain as a cold/occluded front moves through the Ohio Valley.
Timing fairly similar on the U.S. Guidance members that drying
should occur from west-east by Wednesday morning. However...the European model (ecmwf)
lingers the moisture a bit longer before moving it off to the
Long term /Tuesday through Sunday/...
an amplified but progressive upper flow pattern is expected to
dominate much of North America through the period. Expansive
upper low now over the central rockies is forecast to be emerging
through the central/northern plains at the start of the long term
period...then track through the Great Lakes/Ohio Valley and into
New England by the end of the week. A resurgence of the eastern
U.S. Upper ridge then appears probably as more troffing develops
over the western states.
While the main trough axis and associated energy look to track
north of the our region...short wave energy and associated frontal
system will move through PA Tuesday into Wednesday. Forcing with this system
and increasing warm advection will bring a period of unsettled
weather to central PA. Hiest probability of precipitation should occur near the start of
the period then decrease through Wednesday. Behind the front expect
brisk winds and scattered showers changing over to -shsn/flurries
in the higher elevations and Northwest. Lake effect -snsh/flurries
in the northwest will diminish into Thursday as another short-wave
ridge pushes in Thursday and Thursday night. Chances for precipitation
look minimal for the remainder of the period.
Aviation /04z Monday through Friday/...
high pressure and associated dry airmass will build south into
Pennsylvania tonight...bringing a near certainty of VFR conds and
light winds overnight.
An increasingly moist southeasterly flow will develop on Monday...as high
pressure moves off the new eng coast and warm front approaches from
the south. Model soundings indicate MVFR ceilings are likely to
overspread the state from the south during the afternoon. IFR ceilings are
likely by evening over the central mountains there is a just slight
chance of -fzra at kjst...as precipitation arrives Monday evening. Bulk of
model data indicates only rain as precipitation overspreads the area
Tuesday...rain/low ceilings likely.
Wednesday...rain/low ceilings poss. Evening shsn/visible reductions poss kbfd.
Thursday...am shsn/visible reductions poss kbfd.
Friday...no sig weather expected.