Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 050421

Area Forecast Discussion
National Weather Service Burlington VT
1121 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 1111 PM EST Sunday...Stratus have generally cleared across
the North Country this evening, allowing brief window of good
radiational cooling under high pressure before warm frontal
clouds arrive during the pre-dawn period from SW-NE. Cold temps
at 04Z include 11F at SLK, 19F at MPV, and 27F at BTV.
Temperatures will generally level off for the remainder of the
night as mid-level clouds advance rapidly newd, per late
evening IR satellite imagery.

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. Should see some potential road weather
impacts on the morning commute with roads becoming snow covered
in spots, along with low visibility in falling snow. Expecting a
3-6hr period of warm frontal/isentropic ascent driving UVV, with
snowfall amts generally 1-3" by 17-18Z. While these amounts are
relatively light, timing with morning commute could yield some
travel delays, which we continue to highlight via the hazardous
weather outlook and our Facebook and Twitter feeds. Drivers
should exercise caution Monday morning and allow extra time to
reach 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 /04Z Monday THROUGH Friday/...
Through 06Z Tuesday...Generally VFR through 09Z with high
pressure shifting east of the region during the pre-dawn hours.
Thereafter, a warm front approaching from the southwest will
bring developing light snowfall to all TAF locations...generally
09-11Z SLK/MSS, and 11-13Z PBG/RUT/BTV/MPV. At BTV, light snow
should develop around 11Z (6AM) and continue through about 17Z
with 1-3" of snow accumulation expected, with minor impact to
airport ground operations. Anticipate 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 as the warm front shifts to the north and east.
Overall, surface 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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