Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 170750
Area Forecast Discussion
National Weather Service State College PA
250 AM EST Tue Jan 17 2017
A warm frontal system will push into the region from the Ohio
Valley today, followed by a cold frontal passage tonight and
early Wednesday. High pressure will follow and bring mainly dry
conditions with temperatures several degrees above normal from the
middle of the week into the weekend.
.NEAR TERM /THROUGH TODAY/...
Regional 88D loop showing several areas of light-moderate rain
moving east from the Allegheny Plateau to the Central Ridge and
Valley Region at 07Z. Meso Obs showing numerous locations where
the temp has dipped to 32F, which should result in some areas of
light freezing rain and a few hundredths of an inch of ice
accretion on untreated sfcs.
An approx 2-3 hour break in the precipitation will occur over the
Central and SW zones in the wake of this lead area of rain.
Frequent periods of rain will persist across the NW mtns in
closer proximity to the nose of a 50kt swrly LLJ and near the best
LLVL theta-e convergence near the quasi stnry/warm frontal
The axis of the relatively strong LLJ (and a distinct neg tilt
trough axis at 850 mb) will lift NE across central and western PA
late this morning and bring periods of light to mdt rain between
10Z-19Z today. Best freezing rain potential for Central and
Northern PA (covered by the Freezing Rain Advisory) will be
between 10Z-13Z which is unfortunately during the peaks hours of
the morning commute to work and school.
Surface T/Td spreads of 2-5 deg F will allow temps to wet bulb
down by another deg F or two between 07-12Z.
All of the latest model guidance continues to suggest that the
main freezing rain threat will be over the higher terrain of
northern Pa, with a diminishing risk in the valleys and across
southern Pa. Will therefore make no changes to current Freezing
Rain Advisory, but will monitor temps across southern areas for a
possible expansion as current readings are mainly in the mid 30s
with a few locations in the 32-33F range. .
QPF will be light so amounts of ice are not expected to be
significant, but as we have seen several times over the past few
weeks, even a little ice on untreated surfaces can cause
A steadier rain will overspread the region from the west during
the mid to late morning hours today, as the strongest low to mid
level WAA accompanies passage of aforementioned low level jet.
SREF and NAM both indicate the possibility of lingering icing
through mid morning ((14Z) across the high terrain of northcentral
and northeastern Pa (especially between KUNV and KIPT, and points
to the north). The mid level shortwave and associated low level
jet are progged to shift east of the area between 18Z-21Z,
causing rain to taper to spotty drizzle.
Surface warm front is progged to push into the Laurel Highlands
during the afternoon, pushing temps into the 50s down there.
Elsewhere, readings expected to top out in the 40s most places and
the upper 30s over the Mtns north of Williamsport.
Maintained POPs near 100 pct today based on the latest GEFS/SREF
probs and overall favorable pattern of anomalous PWATS and strong
lg scale forcing ahead of shortwave. Blend of model QPF ranging
fairly close to a third of an inch through Today.
.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
Winds turn westerly behind the system by late tonight (west) and
Wednesday (over the east) morning as flow turns more zonal, but
with no real cold air is in sight.
Low stratus and strato cu will combine with a westerly flow of the
shallow cooler air to produce some light drizzle (across mainly
the west-facing slopes and ridgetops of the Alleghenies) and also
areas of ridge- top shrouding fog.
Low temps early Wednesday will range from the mid 30s acrs the
northern mountains, to the lower 40s in the south.
The Wednesday morning stratus/stratocu layer will gradually
dissipate during the mid to late afternoon hours, as a secondary
cfront pushes through and is followed by enhanced deep-layer
subsidence and drying, with only slightly cooler air in its wake.
.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Ridge re-establishes itself over the eastern U.S. for late in the
week, as mild SW flow persists over the midwest. Guidance suggests
energy will dive south along the west coast eventually helping to
strengthen the building upper ridge over the east. We`ll be on the
eastern side of this, so subtle shortwaves sliding into the
Midwest will bring varying amounts of cloudiness to the west (less
in the east) with low end chances for light showers.
Another wave approaches/lifts into the OH valley late next weekend
into next Monday. Again, temps could be marginal at the start
of pcpn overnight Sunday for some ice or snow, but the bulk of
pcpn looks to be rain at this point.
.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
Widespread MVFR to IFR conditions expected through 17/06z TAF
period with rain spreading from west to east across the airspace
by later this morning. Pockets of -fzra remain possible at the
northern terminals thru 15z but temps are marginal.
Wed...MVFR/IFR west; MVFR to VFR central-southeast. Rain showers
west ending Wed ngt.
Thu...No sig wx.
Fri...Sub-VFR possible with rain moving SW-NE.
Sat...No sig wx.
Freezing Rain Advisory until 10 AM EST this morning for