Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1052 am EST Thursday Dec 25 2014
A large area of high pressure will build northeast from the Gulf
Coast region bringing fair weather with diminishing winds that
will last through the end of the week. A weak cold front will
drift slowly across the state Saturday night into Sunday.
Near term /until 6 PM this evening/...
The cold front is clearing the New England coastal waters as of
middle morning...leaving behind a strong pressure gradient and gusty
winds over central PA. The pressure gradient will steadily weaken
today so the noon time end time of the Wind Advisory looks
Colder air aloft and slightly cyclonic low level flow will support
some snow showers across the usual higher elevations of the west
and north through early afternoon. Conditions will steadily
improve this afternoon as inversion heights begin to
lower...cutting off the snow showers and helping to trim the
With surface temperatures expected to be above freezing everywhere any light
snow showers are not expected to accumulate...except for perhaps a
dusting over the highest ridgetops.
Ens mean 925/850 temperatures support high temperatures today ranging from the
m30s over the Allegheny Mountains...to the u40s across the lower susq
Short term /6 PM this evening through 6 PM Friday/...
surface high pressure will build NE into the region late tonight and
Friday...accompanied by decreasing west-southwest wind and clearing skies
across all but portions of the western mountains where some shallow
stratus/stratocu will be present...along with the chance for some
very light snow or -fzdz as cloud temperatures will be just a few to
several degree c below zero.
Low temperatures tonight will be fairly uniform and in the middle to upper
Long term /Friday night through Wednesday/...
potent longwave upper trough exiting the East Coast at the start of
the period will be replaced by upper ridging into the weekend. As
longwave upper troffing is forecast to develop over the western US
starting early in the period and northern stream energy retreats into
eastern Canada...MDT to strong southwesterly flow aloft is then forecast
to dominate the eastern Continental U.S. From late in the weekend through the
remainder of the year.
Medium range guidance is fairly consistent especially early in
the period...but then some differences arise in 500mb flow
pattern after Monday as the European model (ecmwf) moves energy east faster...while
the GFS closes off an upper low over the desert SW.
A northern stream wave is forecast to support a cold front moving
east across the state late in the weekend...possibly stalling
near the Mason Dixon line into Monday as it encounters resistance
from the building upper flow. This front looks to be the main
focus for precipitation in the long term period. With snow to the north and
west...and a mix to rain across the south.
With ridging or southwesterly flow aloft much of the period will feature
above normal temperatures...with a cool down toward normal by new years
Aviation /15z Thursday through Monday/...
Western high terrain terminals will remain MVFR with passing snow
showers dropping visibilities to IFR at times into the late
afternoon or early evening...before conditions improve to VFR.
Central and eastern terminals will be mainly VFR with ceilings
between about 3000-6000' with little more than a brief sprinkle or
Gusty westerly winds will slowly diminish today with the approach
of high pressure leading to fair skies overnight with winds
generally 10-15 miles per hour or less.
Sun-Mon...MVFR to IFR with scattered rain and snow showers.
Wind Advisory until noon EST today for paz004>006-010>012-017-
near term...la corte/Lambert