Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
805 PM EDT Friday Jul 25 2014
high pressure will drift east on Saturday and allow the weather
pattern to become unsettled once again as a series of disturbances
move over 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
Near term /until 11 PM this evening/...
very few if any low clouds to dissipate this evening. Expect temperatures
to drop off rapidly after sunset. High clouds will start to slide
in from the west by midnight...but should not get thick.
Short term /11 PM this evening through 6 am Saturday/...
clouds well-aloft may thicken up through the night...but any low
cloud deck and real moisture does not show up until the daytime on
Saturday. Some higher moisture does show up over the southeast by
daybreak - sneaking in from the south. But mainly westerly flow
at 4-5kft should keep most of the higher moisture moving to the
east and only slightly to the north. Temperatures should therefore get
chilly again...but not quite so cold as Friday morning.
Long term /Saturday through Friday/...
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. A very mild and
somewhat muggy night in store for Sat night.
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 /00z 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 diminished...as 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 Saturday...as
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 mountains...as
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.
Monday...am low ceiling poss West Mountains
Tue-Wed...no 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.