Scientific Forecaster Discussion
Area forecast discussion
National Weather Service State College PA
444 am EST Thursday Feb 11 2016
a persistent northwest wind will keep lake effect and upslope
snow showers going all day. An Arctic blast will deliver the
coldest air of the season for Valentines weekend with dangerous
cold and wind chills expected to impact the area Saturday into
Near term /until 6 PM this evening/...
intense band of snow just lifted out of the backyard. This band
persisted deep into the southeastern cos with accumulations into Lebanon
Colorado. A slight southwest flow is shoving the band to the east. The
band is breaking up but the wind is going back to a nwrly direction over
the western mountains at this time. The convergence line is now a good squall unto
itself - pressing steadily south and east and will impact I-80
shortly. This squall is moving along perpendicular to it/S
orientation. But a quick half inch to inch of snow is possible.
The bands immediately off the lake are reaching into Warren and
McKean cos...but the mean flow is still a little too wrly to push
them too much farther S.
The winds continue to veer through the morning. This should allow
more but shorter bands to occur. However...a good Huron
connection is prognosticated by the mesoscale guidance to focus a long band
through Keri and kfig and right through unv this afternoon. Have nudged probability of precipitation
up in anticipation of this feature. Northern centre Colorado may need an advisory
with snow over the next 18hrs right around 3 inches. But the band
may be 40 miles either direction and the uncertainty leads ME to
hold off for now. Some of the most intense snow there will be over
in just an hour or two.
The wind will make it feel much colder today with wind chills
between -10 and +10 across the entire area all day long. The
blustery conditions will just be a taste of what looks like is on
the horizon for Saturday.
Short term /6 PM this evening through 6 PM Friday/...
the snow showers do begin to taper off in the late afternoon and
evening. The accums should become negligable not too long after
sunset. The end timing of the advisories/warning will be kept as is at
03z. However...many places S of Elk Colorado will see just a flurry or
two in the evening. Temperatures drop into the single digits tonight as
some clearing takes place in the northwest...but the calm air in the southeast
could cause the temperatures there to become colder. Snow pack and calm
air do wonders to make it colder than we think it will be. Will
paint in a dip around the typical fridges of seg and thv - making
them 3-5f colder than the surrounding locales.
The first part of Friday should be quiet save a quick increase in
clouds from the SW as some meager warm advection kicks in ahead of
the well-advertised Arctic front. Some light snow will probably
break out/slide in during the afternoon. Temperatures will try to get into the
20s all over but the persistent cloud cover in the northwest will likely
keep them u20.
Long term /Friday night through Wednesday/...
*impact weather highlights: snow squalls likely with Arctic front
Friday night-Saturday. Frigid temperatures and dangerous wind
chills for Valentines weekend.
Polar vortex dives from Hudson Bay southeast across Quebec and
northern New England Thursday-Sunday. The global models and
ensemble means keep a 'milder' trough pattern in place over the
eastern US into next week. Emergence of southern stream shortwave
and its interaction with the northern stream flow creates the
potential for winter precipitation Monday-Wednesday but with a high degree
of uncertainty/low confidence. A pattern shift to Pacific zonal-to
southwest flow aloft with rising/above normal heights is forecast by
the end of next week. This favors a return to milder weather.
Lake effect and upslope snow showers continue into the weekend
before tapering off on Sunday...as Arctic high builds over the
region. Additional light snow accumulations are likely in the
favored northwest snowbelt and higher terrain along the
The coldest airmass of the 2015-16 winter season remains poised
to arrive this weekend...as a blast of Arctic air delivers a short
duration cold outbreak to central Pennsylvania. Snow squalls are
likely with the Arctic frontal passage Friday night into Saturday.
Maximum/min temperature departures of -20 to -25 degrees below climatology
are forecast Saturday and Sunday. Minimum temperatures Saturday night
into early Sunday morning range from 0f in the lower susq. Valley
to -10f in the northwest alleghenies. The frigid temperatures
combined with dangerous wind chills /-10 to -25 below zero/ will
result in an increased risk for frostbite and hypothermia. Wind
chill headlines are a good bet and precautions should be made now
to protect/prepare for the upcoming cold snap.
A moderation (warming trend) is expected into early next week.
There is still a lot of spread concerning a potential storm system
impacting the northeast early next week. The operational ec
remains more bullish than the GFS in developing a significant
cyclone and has trended even further to the west with is 10/12z
run. Confidence remains low but the system will need to be monitored.
Aviation /10z Thursday through Monday/...
Lake enhanced orographic snow will result in predominantly IFR
visibilities at kbfd/kjst this morning. A slow moving surface trough lying
across central PA will also produce occasional IFR visibilities at kunv until
it/S passage around 11z.
After passage of surface trough...expect a typical lake effect regime
late this morning...with predominantly IFR visibilities from light snow at
kbfd/kjst...possible MVFR ceilings at kaoo/kunv and a high confidence
of VFR conds at the lower elev airfields further east...including
kipt/kmdt/klns. Surface ridge building in from the Ohio Valley should
cause lake effect snow showers to dwindle this afternoon...with
predominantly MVFR conds returning to kbfd/kjst and VFR elsewhere.
A tight pressure gradient over the region is already producing
gusts in excess of 25kts across parts of central PA at 09z...and
model soundings indicate such gusts will become widespread by late
am...as diurnal heating/mixing within deepening boundary allows
winds aloft to mix to ground level.
Arrival of surface ridge should bring widespread VFR conds and
diminishing wind to central PA this evening.
Friday...PM shsn/visible reductions likely...especially West Mountains
Sat...windy. Shsn/reduced visible poss West Mountains...mainly am.
Sun...no sig weather expected.
Monday...PM snow possible.
lake effect Snow Advisory until 10 PM EST this evening for
Lake effect snow warning until 10 PM EST this evening for
Winter Weather Advisory until 10 PM EST this evening for