Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1052 PM EDT Sat Oct 25 2014
a weak cold front will sweep east of the area by morning leading
the way for a brief cool down for Sunday...then increasingly mild
days for Monday and Tuesday. Another cold front should impact the
area during middle week. Much below normal temperatures are possible
late in the week as a highly amplified upper level trough develops
across the northeast states and southeastern Canada.
Near term /until 6 am Sunday morning/...
the cold front is settling quickly through my central zones as of
10 PM. Main development over the last few hours has been the
appearance of a short line of light showers from north of Altoona
to north of Harrisburg.
Overall thinking has not changed...the front will pass rather
quietly with a wind shift from the west-southwest to west-northwest and become a bit
gusty. Well- aligned west-northwest flow in the lowest levels tonight will
combine with a relatively tight pressure gradient and fairly strong
subsidence beneath the right exit region of a powerful 155 knots
upper jet to bring partly cloudy skies and gusty winds of 20-30
miles per hour.
Low temperatures will be in the u30s to around 40f across the northern and
western mountains and low-middle 40s across the central and southeast valleys.
Short term /6 am Sunday morning through 6 PM Sunday/...
Sunday will be breezy and about 10f cooler than Saturday...but
still near to slightly above normal across the susq valley.
Slightly greater departures of about -5f will occur across the
higher terrain of the north and west.
Vertical mixing up to around 4 kft above ground level will tap 25 to 30kt winds
and transport them down to the surface in gusts between 14-22z.
The gusty winds and dry fine fuels could lead to somewhat
elevated conditions for fire spread. However...the relative humidity/S should
not dip below 30 percent...thanks to the cooler daytime temperatures.
Coordinated with surrounding offices and will continue to lean
against posting a Fire Weather Watch at this point.
Long term /Sunday night through Saturday/...
an active jet stream pattern over the U.S. And southern Canada
will dominate the long term period. Successive deep troughs will
progress through the region. These will be enhanced by several
shortwaves before heights build over the eastern third of the
country into the middle of next week. Another system should move
through by the end of the period as a deep trough/falling heights
are forecast to return to the region.
A deep upper level low that should be situated near Newfoundland
should continue to make its way to the northeast as drier...warmer
air settles over the area for Monday. This will be short lived as
a deepening trough makes its way through the Great Lakes region
Tuesday night...through Wednesday morning. As this system moves
eastward...currently expecting a narrow frontal band to move
through Wednesday...though GFS ensembles as well as operational
ec...and GFS differ as to strength...timing and position. Drier
flow will follow in this systems wake.
High temperatures in PA on Tuesday may get into the u60s north and u70s
in the south...or about 15f to 18f above normals. The main surface low
with this long- wave trough will slide from ls to James Bay late
Tuesday into Wednesday. Will therefore draw the Bell curve of probability of precipitation to
surround Tuesday night...but also linger some slight chances in the southern
tier for Wednesday.
The confidence lowers some for the second half of next week. It
does appear that another northern stream system zips in from the west
later in the week...and may have the coldest air of the season
behind it. The trough and colder air appear to move out very
quickly in the progressive pattern.
Aviation /03z Sunday through Thursday/...
line of showers to the south of State College.
Another line of heavier showers across New York state.
Main change to 03z taf package is some adjustment
Earlier discussion below.
Some MVFR ceilings at bfd at jst at times tonight and Sunday
morning...perhaps at aoo for a brief time Sunday morning.
Otherwise...VFR conditions expected tonight and Sunday.
It will be windy at times...especially early on with the
frontal passage...and once the second push of cold air aloft moves
in during the day on Sunday.
Did hit clouds harder on Sunday than guidance...given area
dropping southeast from upper lakes area.
Monday...no sig weather expected.
Tuesday and Tuesday night...gusty winds/rain showers and areas of MVFR possible
late in the day and at night...mainly over the West Mountains
Wednesday and Thursday...brief MVFR and a few showers possible early
Wednesday...otherwise no sig weather expected.
near term...la corte