Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
650 PM EDT sun Mar 29 2015
a ridge of high pressure...bringing sunshine today...will move off
to the southeast by tonight. A cold front will move from the Ohio
Valley across central Pennsylvania tonight into early Monday.
This will be followed by another disturbance that will bring the
chance for more unsettled weather Tuesday. A slow moderation in
temperatures is expected for the latter half of the week ahead.
Near term /until 6 am Monday morning/...
ridge bowing to the east as middle to high clouds increase rapidly
across the western half of PA this evening. Still a pleasant
evening despite the nip in the Air.
Ridge is forecast to continue sliding southeast tonight. Cold front
approaching from the Midwest will bring a chance for snow showers
into western areas by midnight. Short range guidance favors my
western Highlands with the best chance for precipitation...with probability of precipitation
dropping off over central and eastern areas due to downsloping
flow. Ensemble quantitative precipitation forecast of .20" or less looks reasonable with any light
snow accums being mainly confined to the west and north. Warm skin
temperatures for the early part of the overnight should limit amounts
Overnight lows look to bottom out a couple of degree either side of
Short term /6 am Monday morning through 6 PM Monday/...
the front will clear southeastern areas by early afternoon allowing for
the development of an all too familiar blustery and chilly
westerly flow with the usual Post frontal stratocu ceilings and
scattered rain/snow showers that usually favor western and norther
Highs from the middle 30s northwest will run some 10-15deg below normal.
Milder readings over the southeast will actually be not too far from
normal for late March.
Long term /Monday night through Sunday/...
the cold front moving off the East Coast early Monday will be
quickly followed by a shortwave and surface low tracking east-southeastward
from the upper Midwest/Great Lakes through the upper Ohio Valley and
across the Middle Atlantic States on Tuesday. As the previous shift
noted there is still a decent amount of model spread in both the
track and depth of the clipper-like system. The 12z NAM remains
the farthest north and outside the ensemble low spread. The 12z
GFS is a nice fit/compromise in the middle of the deterministic
spread...just a bit slower than the sref/gefs means. The 00/12z
European model (ecmwf) is still on the southern edge of the guidance envelope however it
has adjusted a bit stronger vs. The 00z run. A model blend favors
a narrow swath of precipitation along/north of the surface low streaking southeastward
from the upper Midwest across the northern Middle Atlantic States on Tuesday. The
quick progression and limited moisture should keep quantitative precipitation forecast amts in the
0.10 to 0.30 inch range with this system. Confidence remains low
concerning potential for accumulating snow given time of day and
marginal low level temperatures. The greatest risk is still over northern areas
along/north of I-80 although some higher elevations in south-
central PA could see a little accumulate given an ideal surface low track.
Many areas will likely see a rain/snow mix but with no accumulation.
High pressure should bring dry weather around the midweek before
the pattern turns increasingly unsettled during the second half of
the week. The 12z naefs continues to support a warming trend ahead
of a cold front pushing east from plains/Great Lakes with frontal passage
timing most likely on Friday. Rain showers and perhaps a few thunderstorms
should accompany the cold front followed by a slight cool down
into Easter weekend.
Aviation /00z Monday through Friday/...
VFR conditions will give way to a fast moving frontal system and
local restrictions with snow showers late tonight into early
Monday. A few rain and snow showers for Monday...mainly across the
north and west. Some rain and snow showers for Tuesday into early
Wednesday...as low drops southeast from the Central Plains of Canada.
Monday...chance of light rain/light snow early across the western
half with MVFR reductions. VFR southeast.
Tuesday...chance of light snow/rain...mainly across the northwest half
with MVFR reductions. VFR southeast.
Wednesday-Thursday morning...mainly VFR...as high pressure builds across
Thursday PM-Fri...lowering conditions to MVFR with scattered rain
showers...as a cold front moves eastward.
near term...Watson/la corte