Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1006 PM EDT Monday Apr 20 2015
A cold front will move through later tonight and bring an end to
the steady showers and thunderstorms. A large upper level low
will set up over Ontario and Quebec for the middle and latter part
of the week...ushering in unseasonably cool air which will last
into the weekend or longer.
Near term /until 6 am Tuesday morning/...
10 PM update...have allowed the Tornado Watch to expire.
Convection is still active over the eastern zones...but tops have
come down with the loss of daylight and the main threat now will
be small hail and brief downpours.
Did bump up probability of precipitation into the wee hours according to the latest radar
trends and hrrr which show more showers gathering to our
southwest...slated to move through over the next 3-6 hours.
Surface cold front now crossing the PA/Ohio border and will push east
across the entire County Warning Area by 06z. The cooler moist upslope flow behind
the front will create plenty of low stratus across the western
alleghenies...while most of the Central Valley region will
fluctuate between scattered and broken conditions for the rest of the
Min temperatures will range from the lower 40s across The Laurels and northwest
mountains...to the lower 50s in the southeast.
Westerly wind will increase and gust to the middle and upper 20kt
range late tonight...similar to what we/re currently seeing across
central and eastern Ohio.
Short term /6 am Tuesday morning through 6 PM Tuesday/...
cold advection and westerly upslope flow will lead to scattered rain showers
over the northwest into the day on Tuesday...with variable amounts of
clouds and sprinkles west/isolated rain showers along and just to the southeast of
the I-99/rt 220 corridor. Mostly sunny skies expected for the far
Maxes Tuesday will be around 50f in the northwest and perhaps The
Laurels as well. The lower susq will probably reach the lower 60s.
Long term /Tuesday night through Monday/...
the long term pattern will be dominated by a large upper level
low moving through the northern Great Lakes...and through southern
Canada midweek to the weekend. There is good model consensus
through the Middle Range period. After the front lifts out by Tuesday
morning the upper low hangs around S Canada/New England for
several days keeping fairly brisk west/northwest flow across PA. This will
bring a steady stream of colder air as temperatures slowly slip a bit
lower each day with below normal readings for a several day period
lingering into next weekend. Proximity of upper low will also keep
mention of scattered showers in the forecast. A shortwave should drop
through the region Wednesday afternoon into Thursday morning. This
could drop even colder air into the region bringing the
possibility of snow to the northwest to the central regions of PA. The
models are becoming closer to a consensus solution...however
solution is trending toward the upper level low to become
quasi-stationary and slowly spinning over Quebec.With only a
slight chance for precipitation next weekend. The movement of the
low will dominate the pattern next week with it possibly
retrograding and swinging another trough through the region next
Aviation /02z Tuesday through Saturday/...
a strong surface cold front pushes east across all airfields between
Colder and moist westerly upslope flow in the wake of the front
will quickly lower ceilings at kjst and kbfd back down into the IFR or
LIFR range tonight and early Tuesday with areas of MVFR lingering
during the day Tuesday.
For the susq valley airfields...visibilities will be VFR to brief MVFR
in rain showers/thunderstorms and rain tonight...while ceilings in the MVFR range should be
fairly widespread across the central mountains as the much cooler air
pushes in. Broken ceilings improve to mainly VFR by late morning Tuesday
across this same region.
Tue-Fri...persistent northwest flow pattern each day will favor MVFR ceilings
over the northwest airspace in zob sector...with mainly VFR conditions
prevailing in zny domain. Scattered showers will be possible across all
of the airspace through the remainder of the week.
near term...la corte/Lambert