Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 030451
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1151 PM EST Fri Dec 2 2016

.SYNOPSIS...
An upper trough will move southeast from Canada overnight, and
will bring a chance of rain and snow showers. The region will
remain under cyclonic on Saturday with a chance for more rain
and snow showers. A ridge of high pressure will build into the
north country on Sunday, and will bring fair and dry weather to
the north country from Sunday through Tuesday.

&&

.NEAR TERM /UNTIL 6 PM SATURDAY EVENING/...
As of 1100 PM EST Friday...Best 850-700mb forcing for ascent
with mobile shortwave trough has passed south of our region as
of 03Z. Anticipate some continued light snow shower activity,
mainly confined to orographically favored areas. Lapse rates are
initially quite steep with Froude #s greater than 1, placing
the majority of ongoing snow shower activity over and
immediately downstream of the Green Mtns. The KCXX reflectivity
at 0330Z shows majority of returns across the spine of the
Greens, with some light snow being reported also by ASOS at MVL
and MPV...so the idea of unblocked flow and associated pcpn
patterns is consistent with current observations. Anticipate a
modest temperature inversion forming toward daybreak, per 00z
NAM model soundings, and this may yield some better chances for
orographic blocking and some occasional snow showers in the BTV
area toward 12Z. Again, not expecting any major impacts, but
could see a slick spot or two for the higher elevation roads,
including I-89 from Richmond east to Brookfield. Remainder of
the forecast is on track.

Previous Discussion...An upper trough will move southeast from
Canada overnight, and will bring a chance of rain and snow
showers to the North Country through the remainder of this
evening and overnight. Modest low-level cold advection
associated with this trough will allow snow levels to gradually
fall, from near 1000ft at 00Z, to the valley floors after 06Z.
With WNWLY flow bringing some orographic enhancement, the higher
elevations of the northern Adirondacks and Green Mountains
should see 2-3" of snowfall overnight, with a slushy coating to
1" possible at the lower elevations. Overnight lows temperatures
will range from 33-35F in the Champlain Valley, to 27-32F
elsewhere.

On Saturday, the North Country will remain under cyclonic flow
from the departing surface low pressure area over the Canadian
maritimes. Will go with chance PoPs for rain and snow showers
on Saturday. Highs on Saturday will be mainly in the 30s.

&&

.SHORT TERM /6 PM SATURDAY EVENING THROUGH SUNDAY/...
As of 349 PM EST Friday...Northwest flow persists with cloudy
skies and snow showers, mainly across elevated terrain and
western slopes. Froude number forecasts increasingly blocked
flow throughout the night, but deeper moisture will be
decreasing throughout the night. Therefore, high chance POPs
focused around the terrain and immediate western slopes will
decrease throughout the night with windward valleys possibly
seeing a few snow showers. There is a chance for DZ/FZDZ as
indicated by NAM BUFKIT thermal profiles as moisture layer
shrink from above resulting in lack of ice nuclei. GFS BUFKIT
brings this drier air aloft into the area later with moisture
also eroding from the surface, more in line with stubborn low
clouds than precipitation. At this point in time, confidence not
high enough to include DZ/FZDZ in forecast. Min temperatures
will generally range from the upper teens to mid 20s.

Weakening northwest flow with drying trend will bring an end to
snow showers mid-late Sunday morning as high pressure builds in
from the Great Lakes region. Expect partial clearing of clouds
under the ridge, but lingering low level moisture trap under an
inversion may keep portions of the North Country in mostly
cloudy skies. Max temperatures will range from the upper 20s to
upper 30s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
As of 349 PM EST Friday...Models consistent with regard to dry
Sunday night and only low chances of light precipitation, mainly
across our western counties Monday as a dampening shortwave
trough moves across the region. Increasing clouds and scattered
light snow, with rain mixing in the valleys will be accompanied
by max temperatures in the 30s.

High pressure returns with dry weather, partial sunshine and
light winds Monday night through Tuesday. Temperatures will be
near normal to slightly below normal for early December.

A mid-week storm is poised to affect the North Country, however
models still differ on the evolution of southern stream 500mb
shortwave moving across the SE USA and reflected at the surface
as a coastal low by late Tuesday. Ridging over New England will
affect how far north the 500mb shortwave travels along with
progression of larger 500mb low over south central Canada.
Potential for mixed precip event as the surface high slides
north Tuesday night keeping NE cold air advection near the
surface while warming aloft occurs as precip moves in. Still
much uncertainty.

&&

.AVIATION /06Z Saturday THROUGH Wednesday/...
Through 06Z Sunday...An upper trough is moving through the
region. Scattered snow showers mainly in the higher elevations
are occurring with a chance of some activity at the stations in
the valleys as well. Expect VFR ceilings to trend down to MVFR
overnight, with some local pockets of IFR mainly at KSLK/KMPV.
Through the day Saturday, ceilings will linger at low VFR/MVFR
before gradual improvement back to VFR overall after 21Z.
Surface winds from the northwest overnight and into the daytime
hours at 10-15 knots with gusts up 20 knots expected.

Outlook 06Z Sunday through Wednesday...

06Z Sunday through 12Z Sunday...Mix of VFR/MVFR with local IFR
possible at KSLK in scattered rain/snow showers.

12Z Sunday through 06Z Wednesday...Mainly VFR with high
pressure building in. Periods of MVFR ceilings possible,
especially at KMPV/KSLK.

06Z Wednesday through 00Z Thursday...areas of MVFR/IFR in rain
and snow showers.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...WGH
NEAR TERM...Banacos/WGH
SHORT TERM...KGM
LONG TERM...KGM
AVIATION...MV


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