Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1027 am EDT Sat Jul 4 2015
A storm system will slide south of the area today. A ridge of
high pressure over the upper Great Lakes region will slide to the
southeast and become centered over Pennsylvania on Sunday. This
weather feature will bring dry and warmer conditions for the
second half of the Holiday weekend.
Warm and humid conditions will move back into Pennsylvania early
next week with several opportunities for showers and
Near term /until 6 PM this evening/...
So far timing is holding close to what was expected with the back
edge of the main rain shield now entering my eastern zones. We
will see slow drying as the parent shortwave slides east.
The hrrr still forms some scattered convection over the northern
mountains during the middle afternoon hours...on the edge of the
more solid clouds in an area of differential heating and modest
For this afternoon and evening...expect to isolated showers
across the western half of Penn...with perhaps a few small and compact
thunderstorms and rain drifting southeast across the alleghenies and toward kfig and kjst
in association with an approaching cold front.
Low level cool air damming and the unseasonably cool temperatures should
negate the threat of thunderstorms and rain elsewhere.
Highs this afternoon will vary from just the upper 60s to around
70f across much of the County Warning Area...to perhaps the lower 70s near and to
the west of rt 219 in western Penn. These readings will be some
8-12 degree f below normal.
Short term /6 PM this evening through 6 PM Sunday/...
a weak ridge of high pressure will build southeast into the commonwealth
tonight...before becoming centered over Penn on Sunday.
A deep layer of light wind associated with this high /along with
abundant low level moisture lingering across the region/ will help to
maintain areas of low stratus/or form fog overnight. The fog could
become locally dense early Sunday.
It still appears the mainly favorable conditions will be in store
for evening outdoor activities and fireworks displays...with
little chance of any rain by sunset.
Lows early Sunday will vary from the chilly upper 40s to lower 50s
across the northwest mountains...to the upper 50s across the scent mountains and
lower susq valley.
Long term /Sunday night through Friday/...
Ridge off the East Coast will gradually cede to a mean upper
trough centered west of PA for much of the week...resulting in
regular opportunities for rain. Ecens/gefs indicate the best chance
for rain will accompany passage of shortwave Tuesday night into Wednesday.
Dewpoints ramp up Monday afternoon and diurnally-driven scattered
convection returns Monday afternoon-Tuesday as a weak southerly return
flow kicks in. However...deep moisture and opportunity for
meaningful rainfall should hold off until the approach of cold
front and positive precipitable water anomalies late Tuesday/Tuesday night.
Temperatures will be a few degree f above normal for Monday and Tuesday.
Late in the upcoming week...faster westerly flow will occur
leading to difficulty in timing individual shortwaves sliding
across the state. This will mean keeping mention of scattered
showers and a few isolated thunderstorms and rain for Thursday through Friday.
Temperatures slip back to seasonal normals for Thursday and Friday.
Aviation /14z Saturday through Wednesday/...
Low pressure moving just south of PA is supporting widespread
MVFR/IFR conditions as of middle morning. The associated rain
shield will push east of the area by early afternoon allowing for
slow improvement in conditions for the afternoon.
Can't rule out an isolated shower in spots on the backside of the
departing low as projected by the hrrr. Look for ceilings to
improve and start to clear from west to east this evening into
tonight. Unfortunately this will lead to favorable radiational
cooling conditions and an almost classic setup for widespread
dense fog overnight into the early morning hours of Sunday.
Sunday should feature VFR flying once a.M. Fog/haze Burns off.
Sun...a.M. Fog...otherwise VFR.
Mon-Wed...VFR/MVFR with isolated to scattered showers/PM thunderstorms.
near term...la corte/Lambert