Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1227 PM EDT Friday Mar 27 2015
a deep upper level trough will swing east across Pennsylvania
this weekend...bringing unseasonably cold weather. The upper level
flow will become more zonal next week leading to a slow moderation
Near term /through tonight/...
right entrance region of a 300 hpa jet and the back edge of an
associated NE/SW band of 850-700 hpa fgen continues sliding
slowly east over the lower susq valley this midday hour. Nothing
more than some very light rain/snow is expected to the east of a
kthv to kmui line this afternoon.
Over the northwest mountains and Laurel Highlands...an approaching
upper trough with -2 to -3 sigma 850-500 hpa temperature anomalies and
deepening cold air will combine with a well-aligned northwesterly low level
flow to produce an increasing trend in snow showers...with light
snow accums possible across the higher terrain of the northwest where
temperatures will struggle to reach 32f for a high today.
A few breaks in the multi-layered cloud cover may occur late
this afternoon across the Central Ridge and valley region...along
with the few flurries falling from narrow bands of thicker strato
Highs this afternoon will be much below normal...maxing out near
freezing in the north...and in the middle 40s over the southeast.
Low level cold advection and upslope flow will continue to favor
scattered-numerous snow showers tonight...with an inch or two so
falling across the northwest part of Warren County...and a coating
to an inch elsewhere across the northern and western mountains
Partly-mostly cloudy skies will prevail southeast of the alleghenies with
some flurries and isolated light snow showers early on.
The approach of a shortwave embedded in the larger scale trough
will bring an area of steeper low-middle level lapse rates and a
better chance for snow showers /even across the central mountains and susq
valley/ late tonight into Saturday morning.
Lows in the teens and 20s early Saturday will average some 5 to
15 degree below normal.
Short term /Saturday/...
the coldest 850 air will slide through the area for the first
part of Saturday...accompanied by a few-several hour period of snow
showers that will bring an additional light coating /even to some
places throughout the Central Ridge and valley region/.
Afterward...high pressure building in from the Ohio Valley
bringing brightening skies for the afternoon.
Saturday will see highs from the middle 20s to near 40 northwest to southeast.
Possibly-hopefully the coldest day we see until next fall.
Long term /Saturday night through Thursday/...
the anomalously deep upper trough over the eastern U.S. At the
start of the period will yield to another shortwave that will
temporarily return upper heights to below normal into early next
week. This will continue the chilly temperatures as well as bring the
chance for more mountain snow showers.
The gefs and naefsbc hint that as we enter the first days of
April...the western noam ridge which has plagued US with a never
ending supply of cold air since February...will finally yield to
a more zonal flow and long anticipated moderating temperatures.
The ensemble packages do not exactly go overboard with projections
of eastern warmth however as they maintain a low over hudson's
Bay...but the flow seems destined to come more off the Pacific
into western North America before sliding east...which cannot help
but be milder than the flow out of the Arctic we have seen so much
of for the last couple of months.
Aviation /16z Friday through Tuesday/...
northwest flow in the wake of the cold frontal passage Thursday
afternoon and evening afternoon will combine with an approaching
deep upper trough and embedded shortwave to produce numerous snow
showers across the northwest mountains and Laurel Highlands with high
confidence for MVFR ceilings and occasional MVFR visibilities. Narrow bands of
heavier snow showers and periods of enhanced orographic lift
across the Laurel Highlands will bring brief decreases into the
Generally VFR conditions under a multiple layer of strato cumulus and
altocu/cirrus will prevail through early tonight /04z/ along and
to the east of a line from kaoo...to kunv and kelm. Afterward...
expect ceilings and visibilities to generally lower as an upper air
disturbance tracks east toward the region and increases the areal
coverage of snow showers through Saturday morning.
Northwest winds will average around 10 miles per hour this afternoon and tonight...with
gusts into the middle teens. Wind speeds will increase by about 5 kts
Saturday as the low level pressure gradient tightens up...helping to
create gusts to around 20 kts.
Sat...MVFR/IFR with snow showers north/west. VFR to MVFR central
and east with schc of -shra.
Sun...no sig wx/VFR.
Monday...chance of light rain /light snow early/ across northwest half with
MVFR reductions. VFR southeast.
Tuesday...chance of light rain across northwest half with MVFR reductions.
short term...Lambert/la corte
long term...la corte