Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 042335

Area Forecast Discussion
National Weather Service Burlington VT
635 PM EST Sun Dec 4 2016

Weak high pressure across the area gives way to a weakening
warm front that moves into the region on Monday morning with
widespread light snow through the midday. The snow is expected
to result in some travel slowdowns during the morning commute.
Weather will remain active as we move through the work week
with several additional systems bringing renewed chances of
light rain and snow.


As of 622 PM EST Sunday...IR imagery early this evening
indicates areas of stratus holding on across much of the
Adirondacks, portions of the Champlain Valley, and much of
n-central into nern VT. Have made minor adjustments to increase
cloud cover in spots based on latest trends. As warm front
approaches, will have increasing mid-level clouds from SW to NE
after midnight. Thus, just a small window of radiative cooling
with light winds and partial clearing. Will generally result in
lows in the low-mid 20s, but a few teens are possible if breaks
materialize for a while across the nrn Adirondacks or far nern
VT. Will tend to see temperatures level off after midnight as
mid clouds increase.

Models remain generally consistent with timing of this system
with light precipitation overspreading the southwestern half of
the forecast area between 4-6AM, and generally across all but
far nern VT by 7AM...making for potential road impacts on the
morning commute with roads becoming snowcovered and slick in
spots. Warm frontal bndry is weakening as it moves across, so
expecting a 3-6hr period of generally light snow, with vsby
between 1-2SM in most areas. Highest snowfall amts generally
2-3" across nrn NY, with 1-2" expected across most of VT
(locally near 3" for the higher summits). While these amounts
are light, overall the timing could lead to a slick and slower
morning commute to start the work week and as such drivers
should take extra caution and time in reaching their
destinations. Skies will remain cloudy through the afternoon
hours, with some lingering flurries or light snow showers
expected, especially across the higher terrain. Stuck with
blended guidance for high temps on Monday with highs in the
lower to mid 30s in the valleys and upper 20`s in higher
elevations. Winds look to remain light throughout the
period...initially light SE, shifting W-SW during the afternoon
hours once surface low and associated warm front move east of
our longitude.


As of 226 PM EST Sunday...The forecast challenge this period will
be amount of leftover low level moisture and potential for
areas of flurries/freezing drizzle monday night into
tuesday...followed by slow clearing by Tuesday afternoon. Best
deep layer moisture and lift associated with short wave energy
and weak surface reflection will be well northeast of our region
by 00z Tuesday...but soundings show plenty of low level
moisture between surface and 850mb. Given the lack of any
moisture in the favorable snow growth region and thermal
profiles supporting temps at or below 0C...thinking areas of
flurries and freezing drizzle are likely...especially mountains.
Froude suggests flow is highly blocked with values
<0.50...supporting low clouds and light precip back into the
Champlain Valley on Monday Night. Will mention chance pops with
flurries/freezing drizzle as the predominant precip type at this
time. 2m temps support lows mainly in the 20s mountains to near
30f champlain and saint lawrence valleys.

The question on Tuesday becomes how long the low level moisture
prevails and the areal coverage of low clouds. A weak short wave
ridge aloft and at the surface builds directly overhead...resulting
in very light winds...with some moisture trapped below thermal
inversion. Given recent trends will delay clearing until late
afternoon...champlain valley and northeast kingdom...but given depth
of moisture...some of the higher summits could break out by midday.
Temps will be highly depend upon clouds...but will trend
cooler...with highs mainly in the 30s.

By Tuesday evening...clouds and precip associated with our next weak
short wave energy and ribbon of mid level moisture is quickly
overspreading our region. Thinking light snow arrives southwest
Saint Lawrence County by 00z Weds and quickly lifts from southwest
to northeast across our region by 06z Weds. Latest trends show best
dynamics and moisture splitting our region to the northwest or only expecting light precip amounts. Generally a
dusting to several inches in the mountains...with maybe a spot 3 or
4 inches down by Killington. Expecting little change in temps with
clouds/precip with low mainly in the 20s mountains and near freezing


As of 226 PM EST Sunday...Any leftover precip on Weds morning will end
as a period of light valley rain and mountain snow by 15z Weds.
Any additional light snow accumulation will be confined above
1500 feet as bl temps warm into the mid/upper 30s by midday. A
few slippery spots are possible during the weds morning
commute...but overall impacts should be minimal.

Still anticipating large scale mid/upper level trof to develop
across the eastern conus by late week into next weekend...with temps
trending toward below normal values...especially by next weekend.
This transition will come with a period of unsettled weather on
Thursday...with additional terrain focused snow showers for Friday
into Saturday. Our coldest airmass of the season is still
anticipated Saturday Night into progged 850mb temps drop
between -15c and -17c.

Both CMC/GFS 12z runs show a much weaker and unphased system for
Thursday...with a period of snow showers expected associated with
potent short wave energy and some mid level moisture. Will continue
to mention likely pops with some accumulation expected over the
mountains...but the lack of organized surface low pres and fast
confluent flow aloft will limit significant deep layer moisture from
being advected into our region. Progged 850mb and 925mb temps range
between -8c and -10c on Thursday supporting highs mainly 20s
mountains and 30s in the valleys...very close to normal.

By Friday...favorable upslope winds of 30 to 40 knots develop with
plenty of lingering 925mb to 700mb moisture leftover in mid/upper
level trof axis. This moisture combined with cold air advection
helping to squeeze out remaining moisture in the column will produce
occasional snow showers mainly in the mountains. While not expecting
heavy accumulations...several rounds of 1 to 3 inches of
accumulating snow can be anticipated in the mountains given the
large scale synoptic pattern. A dusting to an inch or so possible in
the valleys. Progged 850mb temps drop between -13c and -15c by 18z
Friday...supporting highs mainly teens mountains to upper 20s/near
30F warmer valleys.

Saturday/Sunday...Similar to yesterday`s data models come back into
better agreement over the weekend...with 1035mb surface ridge
building directly overhead by 00z Sunday. This idea supports a
general drying trend on Saturday into Sunday...with temps running
about 5 degrees below normal based on 850mb temps around -16C. If
skies can clear with surface high pres directly overhead with light
winds...expect temps could approach near 0F at slk/colder valleys of
the Northeast Kingdom by Sunday Morning. At this time will keep lows
mainly in the single digits and teens...but could be colder. Lots of
uncertainty develops with split flow for Sunday into early next week
and associated timing of our next system. Highs only in the teens
mountains and 20s valleys for both Saturday and Sunday.


.AVIATION /00Z Monday THROUGH Friday/...
Through 06Z Tuesday...High pressure is over the North Country
this evening with generally light winds expected overnight.
Despite the high pressure area, still have lingering areas of
stratus clouds, with MVFR conditions as a result at MPV/SLK, and
some lingering VFR ceilings (3-4kft) at BTV/PBG. Not expecting
any precipitation through 08Z. Thereafter, a warm front
approaching from the south will bring developing light snow to
all TAF locations. At BTV, light snow should develop around 11Z
(6AM) and continue through about 17Z with 1-2" of snow
accumulation expected, with minor impact to airport ground
operations. Anticipate a period of IFR at all TAF locations
generally 11-18Z Monday, along with HIR TRRN OBSCD. Light SE
winds will shift light SW-W during the afternoon and evening
hours on Monday. Overall, winds AOB 10kts are expected at all
TAF locations thru the period. May see lingering MVFR ceilings
even as precipitation tapers to flurries/snow showers late
Monday into Monday night.

06Z Tuesday through 12Z Tuesday...BKN/OVC VFR/MVFR with
scattered flurries.

12Z Tuesday through 06Z Wednesday...VFR/high pressure.

06Z Wednesday through 00Z Thursday...trending MVFR/IFR in
rain/snow showers.

00Z Thursday onward...Mix of VFR/MVFR/IFR in periods of light




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