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Area Forecast Discussion
||Wed, Dec 31, 7:00pm EST
FXUS61 KCTP 240344
Area Forecast Discussion
National Weather Service State College PA
1144 PM EDT Wed Aug 23 2017
A large area of high pressure will build southeast across the
region. An upper level disturbance will move across the central
and northwest mountains Thursday afternoon. Sprawling high
pressure will then dominate the weather into the weekend.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Cyclonic flow aloft and a weak secondary cold front are
responsible for some light rain showers currently along and just
north of the NY border. The HRRR suggests one or two of these
showers could survive the trek into the Northern Mountains, but
the better bet is for them to continue to weaken.
Cold air in the form of 850mb temps as low as 6C (1-2sigma
below normal) will slide across the Great Lakes and settle in
for the next several days. Boundary layer decoupling will lead
to calm air tonight which will help to maximize radiational
cooling and help fog to form in the valleys, but some cloud
cover over the west may keep the fog in check. Mins will range
from the chilly mid 40s over the north to around 60 across the
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
A potent albeit moisture starved shortwave trough will approach
the the area Thursday and Thursday evening. Some erosion in
stability is made to occur as the cold pocket aloft moves our
way during the afternoon. SPC does not have us outlooked for
thunder, but with such cold air aloft and the time of year, some
low topped storms would not surprise me. The chances are too
low to include at this time. The best chance of showers look to
be over the higher elevations of the west and north.
High temps Thursday will be about 5-6 deg lower than this
afternoon's (Wed) values, or in the m60s NW-m70s SE PA.
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
An extended period of refreshingly cool, pleasant and dry
weather will continue through the upcoming weekend as high
pressure remains in control of the weather pattern over the
northeast quarter of the CONUS. It will feel more like early
fall than late summer. A few spots in north-central PA could
see morning lows dip into the upper 30s over the weekend.
Global models suggest isolated, terrain-induced convection may
be possible within return flow along the spine of the central
Appalachians later in the period. However, ensemble means favor
a continuation of the mainly dry and seasonable pattern through
the end of August, as upper level ridging building into the
Western U.S. supports troughing downstream over the central and
Interesting to note that the both the 12Z GFS/00Z ECMWF bring
the remnants of Harvey toward the area by early September.
After what appears to be a mainly dry end to the month of
August in central PA, this could be something to monitor down
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
A ridge of high pressure over the region will ensure VFR
conditions and light wind late this evening. Some patchy dense
valley fog is likely late tonight, mainly in the valleys of
northwest Pa. Based on latest SREF, downscaled NAM and LAMP
guidance, believe a period of IFR/LIFR conditions is likely late
tonight into early Thursday morning at KBFD, with a brief
period of fog also possible at KUNV/KAOO/KIPT around dawn.
Elsewhere, believe MOS guidance is overly pessimistic at KJST,
where radiation fog is rare due to its ridgetop location.
Based on climatology and latest model guidance, believe most of
the fog across northwest Pa will burn off by around 14Z. There
is high confidence in widespread VFR conditions the rest of
Thursday. However, can't rule out a brief MVFR reduction from a
passing shower in the afternoon.
Fri-Mon...Patchy AM fog possible, mainly northern Pa.
NEAR TERM...La Corte
SHORT TERM...La Corte/Lambert