Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
1037 am EST Thursday Mar 5 2015
a wave of low pressure will track south of Pennsylvania this
morning. High pressure will build southeast into the state Friday
and Saturday. A strong upper-level ridge will build into the
region early next week. This should provide generally fair weather
and several days of near normal temperatures and relatively dry
Near term /until 6 PM this evening/...
mesoscale banded precipitation has set up over my lower susq
valley counties...prompting an upgrade to a warning from
Schuylkill County south and southwest.
Hrrr shows the banded snow settling steadily south and east this
morning..but not before several more hours of snow of varying
As a weak wave of low pressure rides the front through the
Carolinas...the local area will remain under potent low-middle level
frontogentic forcing in the jet entrance region that short range
guidance shows waning quickly from early to middle afternoon.
Blend of latest model data indicate snow will taper off by late am
across the central counties...with lighter snows lingering until
late day across York/Lancaster counties. Arctic high and associated
dry air mass will arrive early over the northwest counties...resulting in
dry/cold weather the entire day up there.
Some partial clearing appears likely across the northwest counties late
in the day. Elsewhere...model soundings indicate a middle level cloud
deck will linger even after the snow ends. Overcast skies and cold
advection will likely Blunt any diurnal warming and result in
steady temperatures through early afternoon...then falling temperatures late.
Consall output supports daytime temperatures from only around 10f across
the northwest mountains...to the l20s across the southeast counties...another
exceptionally cold day for the time of year.
Short term /6 PM this evening through 6 PM Friday/...
high pressure and below normal low-level temperatures will
dominate the region tonight into late Friday. Unseasonably cold
air...perhaps the last of the significant Arctic surges of our
Based on the low temperatures near and below 0f and the
winds...the potential exists for some areas to experience wind
chills low enough late tonight into Friday which might require an
advisory across the northern tier counties /and perhaps even the
Long term /Friday night through Wednesday/...
surface high pressure ridge will sag just to the south of the middle
Atlantic region Friday night...allowing for an increase in southwesterly
surface winds and clouds across the northwest half of the County Warning Area...with mainly
clear skies and lighter wind persisting across the lower susq
valley...much closer to the surface ridge. Cold temperatures in the low-middle
teens across the northwest mountains Friday will stay nearly steady or even
rise a few degree f Friday night...while a more normal nocturnal temperature
drop of 12-15f is expected across the lower susq valley.
Saturday the temperatures at 850 mb return closer to normal and
high pressure drifts to our south. Pennsylvania should remain
north of this weak high....cutting off any moisture to the
south...keeping the region in weak westerly flow into Monday. The
period should be relatively dry with any frontal precipitation
suppressed to our south and only weak northern stream waves to our
north to generate any precipitation.
So...kept the probability of precipitation low through the period and any light
precipitation would likely be snow as 850 hpa temperatures stay below 0c.
Best chance of any precipitation would be in northern areas should
one of the northern stream waves prove to be stronger than
A ridge is forecast to build over the region Tuesday into
Wednesday and our lower troposphere temperatures should get at
least slightly....above normal....both Tuesday into Wednesday.
This should provide at least 2 days of near seasonal temperatures
for a change. Relatively warm days and cold nights...a good slow
way to melt snow without flooding.
The naefsbc and gefsbc suggest a frontal passage Thursday with
slightly colder temperatures as another high pressure system is
forecast to move over the northeastern United States Thursday into
Saturday next week.
Aviation /16z Thursday through Monday/...
Most of the flying area will remain VFR north of the banded
precipitation that is causing mvr-IFR/LIFR from Johnstown East
through the lower susq valley.
Conditions will slowly improve over southern and southeastern
areas this afternoon...with Lancaster-Harrisburg likely being the
last to enjoy in the improving conditions.
Sun-Mon...MVFR with chance -shsn mainly north and west. VFR southeast.
Winter Storm Warning until 4 PM EST this afternoon for paz033-
Winter Weather Advisory until 1 PM EST this afternoon for
near term...la corte/Lambert