Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
506 am EDT Tuesday Sep 16 2014
an upper level disturbance...weak area of low pressure...and
surface cold front will push east of the region this
morning...bringing an end to the showers. A string of mainly dry
sunny days...and clear to partly cloudy...chilly nights will
follow for the rest of the week. Temperatures will be slightly
below normal on average. &&
Near term /until 6 PM this evening/...
weak...1016 mb surface low was centered in vicinity of kipt at 08z with a weak
cold front trailing southwestward through the kpit area. Upper dynamics
lifting NE of the region and moisture-challenged llvls were helping
to chew up the coverage of showers along this boundary. Will be
lowering probability of precipitation and quantitative precipitation forecast in all areas this morning...and paint a
quicker...stage right exit to the showers.
As low level winds veer around to the northwest later this morning and
afternoon...expect a quick improving trend in most locations.
Upslope stratus will likely persist into the late morning across The
Laurels and northwest mountains...mainly to the west of Route 219. The bulk of
the forecast area - southeast of the Allegheny Front will see a steady
erosion of the clouds with mostly sunny skies expected after 16z.
High temperatures today ranging from the l-M 60s across the higher
terrain of the north and west...to the l-M 70s in the lower susq
valley will be about 2-3 degree f below normal.
Short term /6 PM this evening through 6 PM Wednesday/...
the primary concern for this period is the potential for some
frost late tonight and early Wednesday /and perhaps even a few
locations with temperatures near freezing/ across the northern mountains
Latest...00z mav numbers and 08z GFS lamp guidance remain at the
colder end of all guidance...and have bfd right around 32. Mainly
clear skies and light winds...along with high heights and low
dewpoints /with precipitable waters at or below 0.50 inch/ will be the main culprits
leading to the possible frost up north.
Elsewhere...temperatures will be chilly...but most locations should
see temperatures settle into the u30s and 40s by sunrise Wednesday.
An east/West Ridge of high pressure will build over the middle
Atlantic region and Ohio Valley region Wednesday...accompanied by
abundant sunshine...light wind...and afternoon maximum temperatures near to
slightly below normal.
Long term /Wednesday night through Monday/...
upper trough sharpens over Quebec Wednesday night/Thu...pushing a weak
frontal boundary south toward PA on Thursday. This front will continue
to weaken as it edges southward...but a weak shortwave will slide
overhead from the Midwest. This will bring an increase in clouds
cover along with just a chance for a sprinkle. Northern PA will
get a reinforcing shot of cooler air...keeping highs in the upper
50s to lower 60s.
High pressure then builds across the Great Lakes into a 1030mb
high over New England by Friday...bringing a period of quiet weather
and unseasonably cool temperatures. Morning lows in the 30s are
likely Thursday night/early Friday /especially if skies clear out as
00z gefs and 03z sref temperature plumes suggest that the scattered
frost threat may extend across the central valleys...and even into
the typically cold rural locations of scent Penn. The high temperatures
Friday will be mainly in the 60s as northwest flow continues.
Return flow begins weakly Friday night...taking a little of the bite
out of overnight lows /though still chilly with readings mainly in
the 40s/. But this will begin a warming trend for the weekend.
Temperatures Sat into sun will be 5-8f warmer than Friday...with highs
approaching 80f in the southeast. Lows will be noticeably milder as well
as low level moisture increases in strengthening SW flow.
Heading into Sunday...deepening low centered well to our north
as a trough axis rotates through the Great Lakes will bring plenty
of clouds and a chance for showers. Models still showing large
differences on evolution of this system...with GFS more
progressive and European model (ecmwf) actually bringing a second wave around the
backside of the trough and developing a stubborn closed upper low
over the region. For now will split the difference and hold on to
mention of showers into Monday along with another shot of cooler air
and see how this plays out over next couple of days.
Aviation /08z Tuesday through Saturday/...
showers continue to progress through northwest PA. Rain showers are
heavy at times...producing IFR ceilings and visibilities at bfd. These
conditions will continue through 09z. Reductions across the rest
of the state are possible...though outside of bfd they should
MVFR. The showers will continue their eastward trek...and some
shower formation will be possible in the lower susq before
sunrise. The winds should shift to the northwest after 13z...and
after that conditions should gradually become VFR. At the very
latest by middle to late morning as the cold front moves east of the
area. Gusty northwesterly flow remains probable...though maximum
gusts shouldn't exceed 20mph. Any gusty winds should subside
around sunset...with milder...VFR conditions settling in this
afternoon into tonight.
Some potential for fog Tuesday night...as high pressure
builds over the area.
Mainly dry conditions the rest of the week...as high pressure
Wed-Sat...mainly VFR conditions.