Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service State College PA
1009 PM EDT Friday Jul 25 2014

high pressure will drift east overnight and Saturday allowing
an increasingly moist and unsettled pattern to take over as a
series of disturbances move across the region the later this
weekend and into next week. A deep upper trough will move into the
eastern United States next week and bring another shot of
unseasonably cool temperatures to the region.


Near term /until 6 am Saturday morning/...
moisture increase through Ohio more substantial than previously
indicated...and a large area of showers over central and Northern
Ohio will spread at least isolated showers into northwest and west
central precipitable water in return flow surges above 1.0" after midnight
through the predawn hours and 500 mb shortwave trough traverses the
southern half of PA to be located over the Lehigh Valley by 12z
Sat. Added isolated showers primarily to these aforementioned
areas...despite the presence of any elevated instability and
fairly dry ambient low levels to begin. Areas that do see showers
would only see a few hundreths of an inch at most it appears...but
upstream radar trends in concert with high res local model guidance
necessitate this update.

Bumped up mins slightly with increased cloud cover and shower
chances...with low temperatures ranging from the lower 50s northwest to
around 60 across the far south.


Short term /6 am Saturday morning through 6 PM Saturday/...
Saturday will start off dry in most areas. Timing and placement
of eventual convection will be very dependent on upstream
developments as we come under a robust west-northwest flow aloft. In response
to the approach of a strong upper jet streak nosing into the lower
lakes late in the day...short range operational models and
ensemble packages agree in developing an anomalously strong west-southwest
low level jet and surging it into the region...especially during
Saturday afternoon. Moisture initially looks limited...helping
temper instability much of the day...but increasingly moist air
will be transported into the region along the low level jet bringing higher
probability of precipitation as day gives way to evening. Scattered activity will develop in the
afternoon...with best chances for showers/thunderstorms across the west and north
late after into Sat night as potential mesoscale convective system develops /with isolated
stronger storms poss approaching western border of County Warning Area in vicinity
of a warm front./ Storm Prediction Center brings slight risk area to near west border.
Highs will be near seasonal normals...with humidity creeping back
up and becoming noticable later in the day.


Long term /Saturday night through Friday/...
a very mild and somewhat muggy night in store for Sat
night...after late day convection dies off. Most active day of
this forecast shaping up to be Sunday. Storm Prediction Center shows a slight risk
over Ohio Valley and middle Atlantic region...with focus on a potent
disturbance that will be dropping across the Great Lakes Sunday
and crossing PA Sun night. Effects of mesoscale convective system may impact how event
plays out...but activity should increase through the day as
instability...lift and shear peak. Models continue to differ on
the details/evolution...but atmospheric conditions potent enough
for poss of scattered severe storms...with large hail and damaging winds
the main threats.

Upper trough still lingers over northeast early week as ridge
establishs itself again over western U.S. And near Bermuda. So
continued mention of scattered thunderstorms Monday. Trough slowly fills through
the week...though downward trend in temperatures and dewpoints will bring
a couple noticably cool mornings and below normal maxes before
temperatures slowly gradually rebound later in the week.


Aviation /02z Saturday through Wednesday/...
high pressure and associated dry air mass will provide central PA with
VFR conds and light winds this evening. Earlier concern about late
night valley fog has plenty of middle level cloudiness
is now expected to limit radiational cooling and threat of fog. A
few -shra are possible during the early am hours across southern
PA in association with passage of an upper level disturbance...but
confidence is quite high of VFR conds everywhere through dawn.

Widespread VFR flying conds expected for the rest of
high pressure off the East Coast maintains an influence across PA.
Can/T rule out an isolated late day thunderstorms and rain across the northwest
southwesterly flow draws increasing humidity into the region. However...odds
very small of any restrictions during the daylight hours. Arrival
of a warm front should bring scattered rain showers/thunderstorms and rain to the area Sat night.
Best chance of any impacts in the form of brief wgusts or visible
reductions would be at kbfd.

sun...scattered thunderstorms and rain impacts expected. low ceiling poss West Mountains sig weather expected.


kbfd tied their record min at 39f this morning...then susequently
rose 21 degrees in 3 hours. Wow. All other sites were within just
a few degrees of their respective record mins.


Ctp watches/warnings/advisories...


Synopsis...dangelo/la corte
near term...dangelo/devoir
short term...dangelo
long term...rxr

National Weather Service Glossary of Abbreviations