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fxus61 kctp 160516 
afdctp

Area forecast discussion
National Weather Service State College PA
1216 am EST Tue Jan 16 2018

Synopsis...
a weakening Alberta clipper will track north of PA tonight, and
a secondary low will form south of the region Tuesday and lift
northeast off the mid Atlantic coast Tuesday night. Light snow
will fall over much of central Pennsylvania through Tuesday
night, ending over the southeast early Wednesday morning. A
deep upper level trough will swing through the area later
Wednesday, then be replaced by a building East Coast ridge next
weekend.

&&

Near term /until 8 am Tuesday morning/...
snow out the window now, and many locations in the northwest are white
per web cams. Only a minor change to the snow fall and eventual
totals has been made with this update. All the new 00z data is
not in just yet, but most recent cams and the NAM and arw-WRF
suggest more snow over the central and southeast counties overall, but
still spread out over a long time. Will hold off until all the
00z guid is in to make any tweaks to the wwas, but some change
is possible, esp in the central counties, where 3" of snow now
looks possible, but the whole event will last a little longer
than the 12 hr criteria for an advy. Will let future shift
collaborate with the neighbors on any changes to the wwas.

Prev...
snow has started but is very intermittent - and light - over the
west. All is on time, and no change to amounts for now. New 00z
runs may have some helpful info in a bit, but consensus fcst
appch still the best solution at this point.Temps doing OK, but
some tweaks were made as the clouds are keeping things a tiny
bit warmer.

Even more prev...
low clouds remain banked over eastern third of PA, while a deck
of mid and high clouds stream over central and northern
sections. A break in the mid-high cloud deck has arrived over
the west but will fill in this evening. Some light snow
currently over the Ohio/PA border will swing towards my
northwest zones by evening.

Latest short range guidance continues to track the weakening
clipper system north of the region tonight, producing a swath of
light snow across western and central PA overnight into Tuesday
morning with light amounts for most. Some upslope enhancement
near the Maryland border may produce local advisory amounts
there from late tonight through late Monday morning, and a
Winter Weather Advisory has been posted for Somerset to Franklin
counties for this in collaboration with weather forecast office lwx. Fairly high
snow to water ratios favor advisory criteria snowfall in this
area. Elsewhere, expect a little over an inch across the north
central mountains by dawn, with little by morning across the
southeast. However, some light snow may begin by 10z or shortly
thereafter over the lower susq River Valley, complicating the
morning commute.

&&

Short term /8 am Tuesday morning through 6 PM Tuesday/...
clipper will continue to fill while a weak secondary low
tracking from the southern Appalachians to the mid Atlantic
coast, combined with frontogenetic forcing resulting from jet
streak entrance circulation, could potentially produce several
inches of additional accumulation across the southeast portion
of the forecast area Tuesday/Tuesday night. Latest models and
collaboration with wpc and surrounding offices gives US a long
duration advisory event, with 3 to 5 inches in a 24 to 30 hour
period from 12z Tuesday through 18z Wednesday. Issued Winter
Weather Advisory in collaboration with lwx, phi and bgm.

&&

Long term /Tuesday night through Monday/...
did up pops a little Tuesday night into the first part of
Wed, as the upper lvl trough takes longer to lift out. Not
really a big event, but a longer duration event.

Still looking dry Thursday into Friday. Winds shift more
to the west across the northwest on Thursday, thus more of
a warm advection set up there. The coldest push of air is
down the Tennessee Vly on Wed.

Temperatures by the weekend will be well above normal, as the
upper lvl ridge builds. Took out rain and snow for Saturday.

00z ec has next system so strong over the plains that the cold
front gets push well east of the upper lvl system by late
Monday. Went with a dry fcst aft this.

This warm up not fcst to have dewpoints much above the lower
40s, thus not expecting a lot of heavy rain. More information
in Hydro section below.

&&

Aviation /06z Tuesday through Saturday/...
an Alberta clipper swinging southeast across the mid Atlantic
region overnight into tomorrow will continue to bring snow
showers through the northwest. IFR has spread through bfd with
periods of IFR possible at jst. This will continue to spread
eastward tonight into tomorrow. Expect cigs and vsbys to
continue to drop as the night continues. A weak secondary low
Tuesday through Tuesday night will shift MVFR to IFR
restrictions to eastern areas in light snow, with more scattered
snow showers (and thus more scattered restrictions) for western
areas.

As deep upper trough swings through the region Wednesday,
ceiling restrictions again shift back to the western higher
terrain along with scattered snow showers. Otherwise, primarily
VFR conditions will prevail. Thursday looks to be breezy with
gusts to 15-25 mph.



Outlook...

Tue...restrictions in light snow mainly southeast half. Lingering snow
showers with intermittent restrictions over the northwest half.

Wed...VFR southeast half, but ceiling reductions and intermittent vsby
restrictions across the northern and western mtns as a result
of isolated snow showers.

Thu-Sat..mainly VFR.

&&

Hydrology...
the threat of ice jamming is diminishing. Several cold days
into mid week to form additional ice. Another warm up by the
weekend. Dewpoints for this warm up much less than the event
last Friday.

&&

Ctp watches/warnings/advisories...
Winter Weather Advisory from 5 am Tuesday to 1 PM EST
Wednesday for paz051>053-056>059-063>066.
Winter Weather Advisory until 8 PM EST Tuesday for paz033>036.

&&

$$
Synopsis...devoir
near term...dangelo/devoir

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