Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 122050
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
350 PM EST Tue Dec 12 2017

.SYNOPSIS...
Low pressure forming off the northeast coast at mid afternoon
will track northeast tonight and result in a deep northwest flow
of cold air across the Great Lakes into Wednesday aft. This
will result in snow showers across the mountains tonight and
early Wed.

Another area of low pressure will track across southwestern
Pennsylvania Wednesday night. This low will bring a period
of light snow to the area late Wednesday into early Thursday.

A complex weather pattern will be across the region this
weekend, and early next week. This will result in some snow
showers from time to time, but a moderating trend into next
week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
The cold front has cleared our county warning area, winds have
come around to the west/northwest with gusty winds. The cold air
will continue to move in with with another 10C fall in the 850
hPa temperatures expected overnight. It will turn sharply colder
over the next 8-12 hours and the gusty winds will add some
additional windchill effects to the mix.

Going out tonight or early tomorrow heavy winter coats, hats,
and good gloves/mittens will be in order. Especially at the bus
stops Wednesday AM.

In our western areas, upslope snow showers will accompany the
cold air in the higher terrain mainly from Somerset County up
through Cambria and southern Clearfield. Some accumulating and
blowing snow will be around. Some HRRR runs show enough QPF that
at 20:1 would make 1-3 inches of snow. Perhaps a bit more in
orographically favored areas in the next 18 hours.

In the extreme northwest hour CAMS are more favorable for
accumulating snow. Some HRRR runs shows enough QPF at 20:1 to
produce 5-6 inches and HREFV2 implies higher amounts possible in
northwesternmost Warren County. Our QPF and snow is higher than
the CAMS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Key point is it will be a very cold day with lots of wind.
Windchill values will be below 0F in the northwest and range the
single digits above zero over the southeast. Bundle the kids up
for school.

A very cold December kind of day. Snow guns should be blazing at
ski resorts.

The snow should continue though at lesser rates in the northwest
and in the higher terrain of the southwest mountains.

Clouds will increase during the day as a fairly vigorous Alberta
Clipper zips on towards us. Most models weaken it as it passes
over us. But as the rule of clippers go this one should pass
just to our south, the old school sweet spot.

Most of the larger scale models imply 0.1 to 0.25 inches of
QPF. Highest in southwest mountains, possible. Most of the
potential snow will fall after this period. But the GEFS and
SREF imply some snow could arrive in the southwest in the late
afternoon or early evening. Most of the snow will fall after 7
PM.

I did up QPF and POPS some Wednesday night.

Amounts still below advisory. System is moving awful fast for
much snow.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Complex pattern for late in the week into next week.

I did lower temperatures and dewpoints for the first part of the
weekend, as the northern system looks stronger now, may result
in cold air building southward into the area.

Also cut winds and gusts down, as I have done the last few days,
given the trend away from a deep low on Sunday.

Models show southern branch of the westerlies trying to come
into play on the large scale next week, but for now did not go
real high with POPS.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
The cold front is still working its way across our easternmost
counties. Behind the initial surge of cold air winds have come
around to the west/northwest with gusty winds in the higher
elevations. Gusty winds will slowly spread east.

Low cigs are behind the front. But most of the MVFR/IFR is in
the higher terrain. Snow and blowing snow will affect the
southwestern mountains and northwestern areas for the next 12 to
24 hours. Blowing snow too. KBFD and KJST will be the two spots
to check the weather carefully before take off.

Most other areas main concern will be increasing and gusty
winds. Some snow showers will affect KAOO and KUNV at times but
nothing significant nor long lasting but periods of MVFR will
happen.

Farther east mainly gusty winds.

A short wave could bring light snow into western areas Wednesday
afternoon into Thursday. This could lower CIG/VIS in many
western areas from KJST-KAOO-KUNV but this is beyond our current
forecast period.

Outlook...

Wed...Snow showers with IFR NW Mtns. Sct snow showers with MVFR
NW half. Otherwise VFR.

Wed night...Alberta Clipper could bring light snow and more
widespread reductions.

Thu-Fri...Sct snow showers NW. Reductions west and southwest mts.

Sat...Mainly VFR. Perhaps a snow shower north and east early.

Sun...Mainly VFR. Perhaps a few showers late.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 PM EST Wednesday for PAZ005-
010-017-024-033.
Lake Effect Snow Warning until 1 PM EST Wednesday for PAZ004.

&&

$$
SYNOPSIS...Lambert/Martin
NEAR TERM...Grumm
SHORT TERM...Grumm/Martin
LONG TERM...Martin
AVIATION...Grumm/Martin



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