Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
928 PM EDT Sat Apr 25 2015
weakening low pressure will track south of Pennsylvania tonight. A
weak ridge of high pressure will build south across the state on
Sunday. A persistent upper level trough over the northeastern
United States will favor unseasonably cool temperatures through
the end of the month.
Near term /until 6 am Sunday morning/...
weakening shortwave slipping south of PA this evening. Radar
trends and hrrr suggest dwindling band of rain associated with fgen
forcing in the 8-7h layer will only just graze southern
Somerset/Bedford counties this evening. Some snow even reported at
Garrett Colorado Airport...but precipitation rts/evap cooling probably won't
be sig enough to produce any snow in PA. Northerly flow will advect
drier air into the region later tonight...ending the threat of
rain along the S tier and bringing clearing skies to the northern
Blend of latest lamp/rap output supports overnight lows from the
u20s across the north mountains...to the u30s across the low elevations
along the Maryland border. Have added frost to the forecast across the
northern half of the state...where skies are likely to become
Short term /6 am Sunday morning through 6 PM Sunday/...
narrow surface ridge and associated band of dry air/low precipitable waters over upstate
New York this evening will slide south into central PA Sunday morning.
Thus...see a mainly sunny start to the day. However...upper trough
and associated cool temperatures aloft will be swinging south into the state
by afternoon. Thus...expect plenty of afternoon cumulus and even a few isolated
-shra...especially over the north mountains given the expected sparsity of
coverage and low precipitable waters expect measurable rainfall to be a very low
probability. Thus...will not explicitly mention -shra in forecast
at this time.
18z gefs mean 800 mb temperatures support maximum temperatures from near 50f across the northwest
mountains...to near 60f across the lower susq valley...still well blw
normal for late April.
Long term /Sunday night through Saturday/...
active northern and southern stream split flow pattern across
North America will keep the region in upper level troffiness
through much of the period. The blocked up northern stream...generally
northwest flow pattern over the northeast will tend to shunt southern stream
system to the south of PA.
Early next week a shot of cool unsettled weather arrives as a back
door cold front is nudged southward across PA from an upper low
over new eng. Cool temperatures aloft associated with upper low will likely
lead to a good deal of daytime cloudiness and scattered rain showers /esp over
the mountains/ Monday and Tuesday.
By midweek...this low finally lifts out for good..but digging
trough from upper Midwest will extend into the southeast U.S. By
late week...combined with a southern stream shortwave lifting out
of the S plains toward the East Coast will bring possibility of a
developing storm sliding northeastward off the eastern Seaboard.
Track/strength still quite uncertain...but at this time looks like
we/ll be between that low pressure area and a high over Ohio
Valley...likely keeping clouds and scattered showers around as temperatures
cool back down a bit.
Aviation /01z Sunday through Thursday/...
other than a few showers with perhaps MVFR conditions
at jst later tonight...looking at just high and middle level
clouds at other sites with VFR conditions tonight.
An upper level trough could bring some lower clouds and perhaps
a shower to bfd late Sunday. For now...left forecast for bfd
More in the way of wind and showers for Monday into Tuesday...as
winds shift to the north and upper level heights fall.
Improving conditions for Wednesday into Thursday...as weak high pressure
Mon-Tue...VFR...areas of MVFR with rain or snow showers.
Wed-Thu...no sig weather.
short term...Fitzgerald/la corte