Area Forecast Discussion
Issued by NWS State College, PA-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 171213
Area Forecast Discussion
National Weather Service State College PA
713 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 /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --Regional 88D loop showing increasing rain coverage across the
western half of the CWA...while a few smaller areas of light...to
briefly moderate rain affect the Susq Valley and points east
through the mid morning hours.
Meso Obs showing numerous locations where the temp is hovering
right around 31-32F at 09Z, esp in the vicinity of KUNV and the
mtns to the north.
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
The greatest potential for freezing rain across Central and
Northern PA (currently covered by the Freezing Rain Advisory
through 15Z today) 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 09-12Z as the increasing area
of rain overspreads the region.
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
No changes were made to the current Freezing Rain Advisory. Will
continue to keep a close eye on temps across southern areas for a
possible expansion of the Freezing Rain Advisory 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 north-
central 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.
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.SHORT TERM /6 PM THIS EVENING 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 /12Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --Widespread MVFR to IFR conditions expected through tonight with
periods of rain becoming more showery into Wednesday morning.
Pockets of -fzra remain possible across the northern airspace thru
15z but marginal surface temperatures should limit icing impact.
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.
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Freezing Rain Advisory until 10 AM EST this morning for