Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1133 PM EDT Tuesday Apr 21 2015
a cold front will approach from the Midwest tonight. That system
will spread showers across all of central Pennsylvania on
Wednesday. Cool weather can be expected late this week with
scattered showers possible...mainly over the northern and central
mountains. Some wet snow showers can even be expected during the
nighttime hours Thursday through Friday...mainly across the north
and higher elevations.
Near term /until 8 am Wednesday morning/...
1030 PM update...
good gusts with showers which moved overhead and at kfig and kipt.
However...the best of them should be done now. Coverage of the
showers should decrease through the next few hours.
cellular convection producing lots of radar echoes but hardly any
precipitation is reaching the ground with dewpoints very low. With loss
of daytime heating/instability many of these showers will
dissipate. But very weak forcing under the cyclonic flow lingers.
Potent short wave trough digs into Ohio later tonight and puls cold
air in...sharpening up a front. A more contiguous area of rain
will likely move into the western mountains late tonight. Timing
differs by a few hours among the models...though. Still...the
bulk of the rain waits until after sunrise.
Short term /8 am Wednesday morning through Wednesday night/...
a cold front will pass through the middle-Atlantic on Wednesday
bringing a cold rain to the entire area during the morning and
early afternoon. But additional showers will develop in the northwest
flow Post-front. Wednesday night will become unseasonbly cool and
breezy. Scattered rain showers will mix with or change to
scattered light snow showers over the northern mountains and
Laurel Highlands overnight. A dusting is possible on the higher
elevations Wednesday night.
Long term /Thursday through Tuesday/...
the long term period will start with deep unseasonably cool
cyclonic northwesterly flow around middle-level low pressure centered
over Quebec. This will set the stage for plenty of clouds along
with a few rain and snow showers over the northern mountains and
Laurel Highlands Thursday through Friday. Mainly dry weather can
be expected farther southeast from the central mountains through
the Susquehanna valley but temperatures will be unseasonably cool.
Upper level low pressure over Quebec will lift slightly
northeastward toward the Canadian Maritimes over the weekend
resulting in mainly dry and slightly warmer conditions... however
temperatures will still be below normal into early next week.
Aviation /04z Wednesday through Sunday/...
did add vcsh to ipt on the 03z update.
Cooling tops on the infrared pics.
Earlier discussion below.
Some vcsh this evening...should slowly be on the decrease
overnight...as temperatures cool off. Gusty winds will prevail
for a few more hours...before tapering off some...especially
across the Susquehanna valley...as the gradient weakens there
The upper level trough swinging across the area on Wednesday...will
shift the winds to the northwest. MVFR ceilings will be possible early
across the mountains.
Winds will again be gusty on Wednesday...given the strong April sun
and the abnormally cold air aloft.
Some snow may mix in across the far western and northwest areas toward
00z Thursday...as colder air works southeast.
The coldest day will be on Thursday.
Some slow improvement Friday into the weekend...see outlk section
Thu-Sat... persistent northwest flow pattern will favor MVFR ceilings over
the northwest airspace in zob sector...with mainly VFR conditions
prevailing in zny domain. Isolated to scattered showers will be possible
across all of the airspace through the remainder of the
week...though lesser chances Fri-Sat.
Sun...improving conditions as high pressure builds eastward.