Area Forecast Discussion
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FXUS61 KCTP 032054
Area Forecast Discussion
National Weather Service State College PA
354 PM EST Sat Dec 3 2016
High pressure will build in later today but slide quickly off to
the east on Sunday. A weak frontal boundary passing through Sunday
night will cause light snow in the north and rain or snow in the
south. A storm with mainly rain may affect the area during mid-
week, some mixed precipitation may occur at the beginning of that
.NEAR TERM /UNTIL 7 PM THIS EVENING/...
630 AM update...
Breaks getting larger as the winds have veered a little. However,
stratocu deck is extensive to the west. Will hold the course with
some clearing - mainly in the downslope region. Temps look on
track if not a deg or two too cool right now.
Low pressure over ME and Canadian Maritimes will move to the east
and relax the NW flow - but not until late today and this evening.
Expect more of the same through the daylight hours. Temps should
rise a grand total of 3-5F today. The brisk west wind will
continue. Still looking for an inch or less for accums on the
higher ridges in the NW, and nil elsewhere. Most of what falls
from the sky will just be a flurry or sprinkle.
.SHORT TERM /7 PM THIS EVENING THROUGH MONDAY/...
Flow relaxes tonight as sfc ridge slides overhead for Sunday
morning. Some decrease in cloud coverage is expected overnight,
but it turns right around during the day on Sunday. High/mid/low
cloud progression will darken things again wherever
breaks/clearing does occur. The E/SE will stand the best chance
for complete clearing. Temps will be cooler tonight without so
much wind to keep us well-mixed.
Biggest challenge in this cycle is what kind/how much precip falls
Sunday night from the passage of a weak front. All the models and
most of the GEFS members crank out 0.05-0.20 inches of QPF for Sun
night as the feature is carried steadily through by mainly zonal
flow. Most of the precip should be snow, but it is not likely to
stick in many places SE of the Allegheny Front. Just the highest
hill tops of the SE may get a dusting. For a few runs, a weakness
exists in the QPF right through Central PA from W-E. This seems to
be a disconnect between the moisture and the left-exit region of a
150kt jetlet which passes right over the state. Temps are marginal
for accums, and QPF is light. Have drawn 1-2 inches across the
nrn tier of counties. It is a nighttime event, and temps in the
nrn tier are much more likely to be sub-freezing all night.
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The ridge moving to the east will be followed by a large
mesocyclone emanating for a large upper level low moving into the
northern Great Lakes region. There is decent agreement in
bringing the upper low up through the Ohio Valley on Tuesday as a
shearing out shortwave and diffuse the surface low. Unless cold
air damming traps enough chilly air in the low levels to make for
some freezing rain, the precip type with this midwest system looks
to be mainly rain. Have raised POPs into the categorical range as
it seems unlikely that we will get missed.
The end of the week brings some model disagreement with the
GFS/GEFS being faster than the ECMWF with the next large upper
trof and frontal system. Either way, precip looks like a good bet
around the Thu/fri period as all solutions eventually bring this
trough through. So predictability is increasing, but timing issues
remain. Best bet for precip at this point is mainly rain over the
SE as decent push of warm air lifts ahead of the system, with a
rain/snow mix further north where warm air will not infiltrate as
Behind the trough, looks like a chilly weekend in store with a
potential sharp dropoff in temps.
.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
12Z satellite loop showing stratocu deck beginning to break up
across Eastern Pa as inversion height lowers. CIGs ranging from
low MVFR at KBFD/KJST to between 4-5kft at the lower elevation
airfields, including KIPT/KMDT/KMDT. The main aviation concern
this morning will be at KBFD/KJST, where moist WNW flow forced to
ascend the Appalachians will create borderline IFR CIGs and
occasional snow showers. Downsloping flow will result in
progressively better conditions further east, with MVFR cigs
likely at KUNV/KAOO and VFR conditions at KIPT/KMDT/KLNS.
High pressure approaching from the west will cause snow showers to
diminish across the NW Mtns later today. However, model soundings
still indicate persistent MVFR CIGs at KBFD/KJST through this
WNW winds should continue to gust to around 20kts today, then
expect diminishing winds this evening as high pressure builds in.
Sun...Light snow/reduced vis possible at night, mainly NW Mtns.
Mon...No sig wx expected.
Tue...Mixed precip/low CIGs possible, especially late.
Wed...Lingering low CIGs possible.