Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
702 am EST Sat Nov 28 2015
a slow moving cold front will sag southward across central PA
today. High pressure will build southeast into the region Sunday
and Monday. An upper low over the Midwest will lift through PA
Near term /until 6 PM this evening/...
cold front at 1130z now stretches from kavp to just south of kpit.
Satellite- derived precipitable water loop showing atmospheric river of anomalous
precipitable waters extending from the eastern Pacific all the way through PA ahead
of approaching cold front.
However...lg scale forcing expected to be relatively weak...as
parent shortwave tracks well north of PA. Thus...expect rainfall
amts to be light with amts of no more than a tenth of an inch in
most spots. Highest /categorical/ probability of precipitation are placed across the
Allegheny plateau due to orographic enhancement and lowest
/likely/ across the susq valley.
Temperatures not expected to move much from am lows across the north mountains due
to low level cold air advection. A later arrival of the front across the southeast
counties should result in one more mild day...with maximum temperatures
approaching 60f across southern valleys.
Short term /6 PM this evening through 6 PM Sunday/...
a wave along cold front should spread a steadier period of rain
across the southern half of the state tonight. Based on 00z gefs
and oper runs...have increased probability of precipitation to near 100 percent across the
southern counties. Additional rainfall of anrd a quarter inch
appears likely over southern PA tonight based on blend of model quantitative precipitation forecast.
Drier air arriving in wake of shortwave should cause clearing
skies tonight across northern PA with min temperatures in the 20s.
Overcast skies elsewhere should hold temperatures well above freezing.
00z guidance supports brightening skies from north to south on
Sunday...as high pressure and associated low precipitable water air mass works south into
PA. Will maintain a chance of lingering -shra across the southern
counties through late am...then dry weather anticipated for the balance of
the day. Ens mean 925 temperatures between 0-4c should support maximum temperatures
from the l40s over the north mountains...to around 50f across the lower susq
valley...still just a bit above seasonal norms.
Long term /Sunday night through Friday/...
fair/seasonable weather expected sun nite/Monday...as short-wave ridge
moves through. Upper low approaching from the Midwest should
spread precipitation into the area Monday night. Warm air aloft
should keep most of it as rain. However...can/T rule out some
patchy freezing rain for a brief period Tuesday morning across the
north mountains warm front moves through Tuesday as the storm center
moves northeast across the Great Lake region. The associated cold
front will then sweep east across PA on Wednesday. Behind the
front expect brisk winds and scattered showers changing over to
-shsn/flurries in the higher elevations and Northwest. Lake
effect -snsh/flurries in the northwest will diminish into
Thursday as another short-wave ridge pushes in Thursday and
Thursday night. Friday becomes more uncertain. Models are trending
that a storm system will move across to our south. We can expect
south clouds from this system across the southern zones and a
slight chance that precipitation would work north into the lower
Aviation /12z Saturday through Wednesday/...
lower ceilings across northwest PA...as the the leading edge of
the cold front moves into north PA.
Still great visibility across the areas east of the
Expect conditions be on the decrease today...as the
front drops southeast.
Some improvement from north to south late tonight into
Sunday...as a large high builds southward from eastern
Sun...am rain/low ceilings possible...mainly southern PA.
Monday...no sig weather expected.
Tue-Wed...rain/low ceilings possible.
high temperature of 67 degrees in aoo yesterday...11/27...broke
the record of 65 degrees set in 1988.