Area Forecast Discussion
Issued by NWS State College, PA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KCTP 131226
Area Forecast Discussion
National Weather Service State College PA
726 AM EST Fri Jan 13 2017
A cold front will slide southeast and off the mid atlantic coast
today as a large area of high pressure builds over the upper great
lakes as slowly filters colder air into the state into Saturday.
An upper air disturbance will link up with a weak trough of
surface low pressure nosing in from the Ohio River Valley late
tonight and Saturday to bring periods of light snow to central
and northern parts of the state, and mixed precipitation or
freezing rain across the south. Another area of high pressure will
build east into the region for Sunday with some sunshine,
seasonably cold temperatures and a light northwesterly breeze.
Milder conditions will work back into the area for the middle of
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Sfc cold front has pushed just south and east of PA early this
morning, but plenty of shallow and warm strato cu persists in its
wake across most of the forecast area, with nothing more than a
sprinkle or flurry expected.
The diurnal temp curve will be quite flat today as moderately
strong llvl cold advection will compensate for any fleeting
clearing, and the downslope nwrly flow into the central valleys
and susq region.
Max temps this afternoon will be mainly a few deg F cooler than
09z temps, except for the SE where highs in the lower 40s will be
some 5-7F cooler than current observed temps.
Any blue skies revealed by the dissipating shallow strato cu deck
during the late morning and afternoon hours will get quickly
topped by a shield of thickening mid and high clouds streaming in
from the WSW.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
This will be the main period of adverse weather over the upcoming
weekend, as the entrance region of a potent and nearly quasi-
stnry east/west jet max at 300 mb becomes situated across the
Light to moderate isent upglide develops as a result of increasing
FGEN across much of the region during the late morning and
afternoon hour Saturday with the NAM, SREF and NBM the most
aggressive/northern model solutions with the precip shield. 13/00Z
EC appears to be the more southern outlier attm.
Pulses of slightly above freezing air at different depths in the
low-levels will nose into swrn/scent PA late tonight and
Saturday, supporting the likelihood for a wide mixture of precip
across the SW zones, and a much better chance for a light 1-2 inch
snowfall across the region northeast of the RT 322 corridor.
Collaborated with WFOs PBZ, LWX and PHI and posted a Winter
Weather Advisory from 05Z Sat-05Z Sunday for our 4 swrn zones, as
a result of the bulk of the precip expected to be in the form of
freezing rain there. The light snow/sleet mix currently doesn`t
warrant the issuance of a Winter Weather Advisory further north
and east at this point.
Although QPF amounts are light...to as much as around 0.20-0.3
inches via some members of the SREF, there is quite a bit of
spread, reflecting some model uncertainty/gradient with respect to
the northern edge of the precip shield, not to mention differences
in the timing and precip amount.
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Light mixed precip (or very light snow) may linger for a few
hours into the evening hrs Saturday across southern and eastern
portions of our CWA. Little if any additional snow or ice accum is
expected. Partial clearing or better will occur after midnight
Sat with just a few flurries possible across the northern and
western mtns of the state.
High pressure will build into the area from the Upper Great Lakes
on Sunday, supplying us with fair, chilly weather and relatively
light nwrly wind.
High temps will rebound by some 5-8 deg F on Sunday with respect
to Saturday`s highs.
A warm front will lift back northeast from the Ohio River Valley
early in the upcoming week. This airmass boundary will be preceded
and accompanied by a light, wintry mix of precip during the
morning hours Monday.
A good portion of next week is shaping up to be mild and showery,
as bulk of med range guidance shows a building ridge along the
east coast with a surface low track west of PA. It looks like
there will be enough low lvl cold air to support some ice ahead of
first low on Monday.
For Tue-Thu, med range guidance placing PA in deep southerly flow
ahead of a trough over the midwest. Plume of anomalous PWATS over
the region supports the idea of warm and showery weather. GEFS
temp plumes showing no below freezing temps (even at BFD) Tuesday-
Some variation with potential waves on the front by late next
week, thus did not want to take mention of showers out for late
Thursday at this point.
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --MVFR-IFR cigs across the wrn 1/2 of the airspace should dissipate
by afternoon. VFR conditions expected this afternoon into tonight
with mid-high clouds lowering from south to north into Saturday.
Added PROB30 at JST from 1406/1412 as wintry mix spreads northeast
from WV. Odds favor wintry mix over the southern 1/3 of the
airspace on Saturday but potential is there for snow/ice to
expand farther to the north.
Sat...Sub-VFR likely with wintry mix southern 1/2-1/3 airspace.
VFR northern 1/2.
Sun...VFR/No sig wx.
Mon-Tue...Sub-VFR likely with chc of freezing rain/rain.
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Daily record maximum temperatures were set at Harrisburg (65),
Altoona (66) and Bradford (56) yesterday 1/12/17. A daily
rainfall record of 1.92 inches was also set at Bradford.
Winter Weather Advisory from midnight tonight to midnight EST
Saturday night for PAZ024-025-033-034.