Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
712 PM EDT Wednesday Apr 1 2015
High pressure will move off the Delaware-Maryland-Virginia coast tonight. Thursday
will turn much warmer ahead of an approaching frontal boundary.
This front should stall out across Pennsylvania Friday into
Saturday...allowing a significant wave of low pressure to form and
ride northeast along it...bringing rain then perhaps a changeover
to wet snow across central and northwestern Pennsylvania.
Near term /until 7 am Thursday morning/...
High pressure extends from upper state New York to just off the Delaware-Maryland-Virginia
peninsula. Most clouds have dissipated leaving behind clear to
scattered skies as Sundown approaches.
The overnight will be dry and uneventful with lows generally in
Short term /7 am Thursday morning through 6 PM Thursday/...
high pressure will slide southeast across the state
tonight...before sliding off the Virginia/NC coast on Thursday.
Clear to partly cloudy skies will occur tonight/early Thursday
with light/variable or a light S-SW wind. Lows tonight will
be generally in the lower to middle 30s.
Middle and high clouds gradually increase/thicken-up from the west
Thursday afternoon and evening. Prior to that...we should see
temperatures reach the upper 50s to middle 60s /NW to southeast across the cwa/.
Long term /Thursday night through Wednesday/...
significant moisture return out of the Gomex will will lead to a
rather widespread precipitation event across central Pennsylvania
late this week. A cold front dropping southeastward out of the
upper Midwest on Thursday will intersect this deep moisture/plume
of above normal precipitable waters flowing northward. The boundary is expected
to slow down and become quasi-stationary over PA on Friday before
shortwave energy pressing southeastward from the Great Lakes toward the
coast pushes the front through the area by 12z Saturday. Model
guidance continues to converge on two frontal waves riding northeastward
along the boundary with the second surface low developing into a
seasonably strong cyclone as it tracks northeast along the northern
middle Atlantic and New England coasts.
A broad area of warm advection precipitation will impact the area
ahead of the cold front and associated frontal waves. A multi-
model and ensemble blend of quantitative precipitation forecast amounts with local bias correction
results in widespread 0.50 to 1 inch amounts with the potential
for 1-2 inch totals over the western 1/3 of the County Warning Area. These amounts
could produce some minor flooding and wpc has issued a slight
risk for excessive rafl targeting western/southwestern PA. As the low deepens
while lifting towards the northeast Friday night...a deformation
zone is forecast to become established over northwest PA/western New York into
interior New England. Confidence is increasing in the potential
for a few to several inches of wet snow over the northwest mountains as precipitation
transitions from rain to snow...and have updated the severe weather potential statement to
reflect this change in overall confidence.
A period of gusty northwest winds on the backside of the departing low
will lead to an unseasonably cold and brisk start to the Easter
weekend with below normal temperatures...trending warming into
the middle of next week. The pattern should dry out for the most
part with another potential wet period around 7-8 April.
Aviation /00z Thursday through Monday/...
high pressure building east into PA from the Ohio Valley. A
streamer of clouds/moisture on northwest flow off of Lake Erie is
producing VFR broken-overcast ceilings across the northern and central
mountains airfields...diminishing the otherwise sunny day that is
going over eastern sections.
Ceilings should scatter out early evening as winds diminish under the
high center and subsidence from the high. VFR conds expected for
remainder of this period.
Thursday morning...mainly VFR...as high pressure builds across the
Thursday PM-Fri...lowering conditions to MVFR with scattered rain
showers...as a cold front moves eastward. Gusty SW wind developing.
Sat...low probability for rain showers /mixed with snow showers north/.
Reductions poss mainly northern mountains
Sun...mainly VFR. Front will approach from the north late in the
Monday..possible area wide reduced ceilings and visibilities in precipitation.
near term...la corte/gartner
short term...la corte/gartner