Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
515 PM EDT Tuesday may 5 2015
a slow moving cold front will sag southeast and become nearly
stationary over into Thursday. This will lead to daily chances
of showers and thunderstorms. High pressure will return for the
end of the week. This week will be much warmer than normal.
Near term /until 9 PM this evening/...
slow moving front along PA New York border will drop southward into PA
overnight. This will be the focus for showers and a few
thunderstorms through this evening. First batch of showers about
to exit the eastern zones will lead to some brightening/psunny
skies across central and Susquehanna valley regions. Second round
of showers/thunderstorms now moving across northwest counties. Forcing associated
with this batch...obtuse shortwave within zonal flow over eastern
Great Lakes...will lead to expanding area of mainly scattered
convection across western mountains into evening hours as temperatures warm across
Short term /9 PM this evening through 6 PM Wednesday/...
wavy boundary stalled over the state will keep scattered showers
somewhere in the County Warning Area during the period. Hiest chance of precipitation is
likely to be over western and northern mountains...closer to shortwave energy
emerging from the plains. Scattered rain showers are possible in the morning.
The daytime instability will likely allow more showers during the
afternoon. Not so sure on coverage at this point...but best chances will
be in the SW in close proximity to the boundary and up against the
more-moist west-northwest 800 mb flow.
Long term /Wednesday night through Tuesday/...
forcing along the boundary should weaken with showers decreasing
in covering over south-central PA Wednesday night into early Thursday...as
an upper level ridge builds over the eastern half of the nation.
The synoptic pattern will have a decidedly Summer-time look and
feel through the weekend with high confidence in above normal
temperatures through the weekend. The precipitation pattern favors isolated
to widely scattered diurnal convection Thu-sun. A frontal system
approaching from the Great Lakes and Midwest will support an
uptick in probability of precipitation by early next week. Highest ndfd probability of precipitation are Mon-Tue.
Confidence in temperatures drops off to average by this time with
models and ensembles somewhat at odds with respect to maintaining
a strong upper ridge vs. A cooler more confluent flow aloft.
Overall have not deviated significantly from previous forecast
package and favored more of a mixed blend for days 7 and 8.
Subtropical low near/along the southeast coast is expected to
stay far enough south and not impact the area with precipitation or
Aviation /21z Tuesday through Sunday/...
scattered to numerous showers will focus along a slow moving front
dropping southward into PA overnight. Sites should be VFR much of
the time into this evening...then drop to MVFR in showers later
this evening then continue in areas of fog overnight. Tomorrow
will be similar to today with scattered showers/thunderstorms but VFR much
of the time.
Thursday...am low ceilings/fog poss...especially kjst.
Fri-Sat...isolated PM thunderstorms and rain impacts poss West Mountains
Sun...scattered to numerous showers/thunderstorm activity with cold frontal passage.