Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
242 am EDT Thursday may 7 2015
high pressure will build over the eastern states today and Friday
and begin an extended period of unseasonably warm and humid...but
mainly dry weather. The next chance for more-widespread showers
and thunderstorms will come early next week as cold front pushes
east from the Ohio Valley.
Near term /until 8 am this morning/...
low clouds in two big patches over the region at 0530z. A break in
the clouds over kipt/kunv and areas directly to the south will
likely close up through the rest of the night. While some breaks
in the clouds are expected to last into the morning. Much of the
area should remain cloudy. No real risk for a shower...but the
weak upslope flow could wring out a patch of drizzle. Temperatures will
likely move little through sunrise.
Short term /8 am this morning through 6 PM Friday/...
a ridge pumps up over the eastern states Thursday and
Friday...and should cut off the moisture streaming in from the
west. But before the moisture decreases too much...the daytime
heating on Thursday could pop isolated/scattered afternoon rain showers off over the higher
terrain - mainly over the northern mountains and The Laurels where surface
based convective available potential energy will once again get near 1000 j/kg during the late
afternoon. Will maintain just 20-30 pop there.
A stray...brief shower is possible outside that area...but not
enough of a chance exists to mention precipitation at this point. Much of
the morning clouds should dissolve from SW to NE as the warm
frontal boundary gradually lifts north. Given the already cloudy
and very mild warm start to the day...maximum temperatures will reach about
10f above normals.
Long term /Friday night through Wednesday/...
the synoptic pattern will have a decidedly Summer-time look and
feel with high confidence in above normal temperatures through
the upcoming weekend and possibly into Monday. The precipitation pattern
favors isolated to widely scattered diurnal convection Friday-sun with an uptick
in coverage likely Monday-Tuesday ahead of a cold front pushing east from
the Ohio Valley. Highest ndfd probability of precipitation continue to be focused in the Monday-
Model and ensemble guidance is now providing better visibility in
a transition from ridge to troughing pattern by day 7-8/next
Tuesday into Wednesday. Low pressure should track through the
eastern Great Lakes with a trailing cold front crossing central
PA. A cooler westerly flow should follow with high pressure
building in through mid-week. Confidence has increased in
temperatures cooling down to near normal levels with one or two
relatively chilly mornings possible by late in the week especially
in the northern zones.
Latest model quantitative precipitation forecast/S suggest moisture axis associated with subtropical
or tropical low near/along the southeast coast may be trying to
extend a little farther northward through the middle Atlantic Piedmont than in
previous runs. That said the system is still expected to stay far
enough south to not directly impact the area with significant
Aviation /06z Thursday through Monday/...
partial clearing...combined with a nearly calm wind and wet
ground from yesterday/S rain...will set the stage for patchy fog
overnight. Current observation...as well as latest sref...hrrr and lamp
guidance all indicate a high likelihood of continued LIFR at kbfd
through 12z. Elsewhere...patchy stratus will complicate the forecast by
holding temperatures up and diminishing the fog potential in spots. Will
rely on blend of sref and latest hrrr...which place the highest
potential of IFR conds from kaoo/kunv/kipt nwrd...with only a
slim chance of sig reductions at kmdt/klns. The topography of kjst
/on the Ridgetop/ is unfavorable for radation fog and suggests
predominately MVFR or better conds are likely there early this am.
Any fog/low clouds should mix out between 12z-14z based on model
soundings. A ridge of high pressure over the area should ensure
widespread VFR conds and light winds for the rest of today. Can/T
rule out an isolated late day thunderstorms and rain developing along The Spine of the
Allegheny Mountains in the vicinity of kjst/kbfd. However...odds of
even a brief reduction appears low.
Friday...patchy am fog possible. Isolated PM thunderstorms and rain impacts poss West Mountains
Sat-sun...am fog poss. Isolated PM thunderstorms and rain impacts poss West Mountains
Monday...scattered PM thunderstorms and rain impacts possible.
near term...dangelo/la corte