Area Forecast Discussion
Issued by NWS State College, PA-- Highlight Changed Discussion --
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FXUS61 KCTP 181117
Area Forecast Discussion
National Weather Service State College PA
617 AM EST Wed Jan 18 2017
A cold front will push east across the region today, and will be
accompanied by a few brief rain showers. High pressure will
follow and bring mainly dry conditions later today, right into
early Friday. Low pressure over the midwest will push a warm front
north across the commonwealth Friday, that will be preceded by a
several hour period of light rain. Daytime Temperatures across
most of Central Pennsylvania will be 10 to 13 degrees above normal
with departures even several degrees more for overnight lows.
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A rather vigorous, 115 kt westerly upper level speed max rounding
the base of a compact, but quite potent upper level shortwave
trough will bring plenty of clouds and a scattering of light rain
showers this morning. Westerly sfc wind gusts around 30 kts
earlier across the Laurel Highlands (linked to the thermally
direct descending branch of the aforementioned jet streak) has
moved east across the stagnant, stable and foggy airmass across
scent PA and the wind gusts have been greatly limited mixing down
to the sfc.
Will consider canceling the Dense Fog Advisory a few hours early
as only several pockets of 1/4SM fog remain at 08z.
A light to moderate westerly sfc breeze will develop across the
Central Ridge and Valley Region and the Susq Valley, helping to
mix out the shallow, cool, moist near sfc air during the mid
morning hours. This will help to quickly improve vsbys.
Look for a rather murky start to the day today, with low clouds
gradually lifting and breaking up by late morning into the
afternoon as a secondary cold front brings a stronger push of
cooler-drier air to the region.
The new airmass will not be especially chilly, with the cold air
very marginal and barely deep enough to produce much more than
isolated-sctd light snow/rain showers in the wake of the secondary
cfront (thanks to 850 mb temps of just -2 to -4C). The most
numerous snow showers will occur as usual just inland from Lake
Erie and across our far NW zones. A light coating of snow could
occur there at elevations over 2000 ft MSL.
Low temps early today will range from the mid 30s acrs the
northern and central mtns, to the lower 40s in the south.
Gradual improvement is expected as the Wednesday wears on...but
it will be a slow process as 5h low drops ESE to the Del Marva by
afternoon...helping a secondary front drop across the area to
signal improvement in the afternoon. Skies will be mostly cloudy
throughout with some brightening mid to late afternoon south
central and southeast. Highs will range from the upper 30s north
to around 50F southeast.
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/...
A shallow, bkn-ovc layer of mild and mainly non-precipitating strato
cu (topped by periods of Alto Cu clouds) will hang around late
today and tonight as the primary 850 mb ridge axis stays west of
our area (and across the upper Great Lakes and Middle Ohio River
Isolated to scattered flurries or brief rain/snow showers will
drift over the Allegheny Plateau of northern and western PA.
Little or no accumulation is expected. Some breaks in the low
cloud deck will develop late today/tonight over the SE 2/3rds of
the CWA, and remain through the day Thursday.
Low temps tonight in the upper 20s to Lower 30s will be near to
slightly below normal high temps typically experienced in the area
during Mid January.
.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
-- Changed Discussion --1020 MB sfc ridge builds NE and over central PA and upstate New
York Thursday night with a sharp upper ridge builds over the NE
states (sliding from the spine of the Appalachians to the Eastern
Seaboard by midday Friday).
The main weather maker for early in this period will come in the
form of a warm from that will lift north over the state during
the day Friday. Operational model and EFS consensus us for a few
periods of rain to occur Friday - primarily during the daylight
hours as the nose of a 40-45 kt swrly LLJ helps to transport a few
bands of relatively strong 925-850 mb Theta-E convergence over the
state. Rainfall amounts should be between 2 and 4 tenths across
much of the forecast area during the Friday period.
The upper ridge re-establishes itself over the eastern U.S. over
the upcoming weekend, bringing mild and mainly dry conditions
Saturday, through at least the mid morning hours on Sunday.
Daytime Temperatures across most of Central Pennsylvania will be
well above normal, but the departures for overnight lows should be
greater by several degrees more throughout the entire extended
Another wave approaches/lifts into the OH valley late in the
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. However, some guidance
suggesting enough presence of cold air to for wintry p-types
across northern PA.
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.AVIATION /11Z WEDNESDAY THROUGH SUNDAY/...
Transition to westerly flow will spell improving conditions east
of the Allegheny Front with VLIFR-IFR trending to MVFR/VFR by 15z.
IFR to LMVFR cigs will likely persist at KBFD/KJST through the
period before slowly improving on Thursday.
Thu...BCMG VFR west. No sig wx.
Fri...Sub-VFR likely with rain moving SW-NE during the day.
Sat...Sub-VFR possible with chc of rain increasing south-north.
Sun...Sub-VFR likely with rain developing.
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