Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 050900
Area Forecast Discussion
National Weather Service Burlington VT
400 AM EST Mon Dec 5 2016
-- Changed Discussion --A weakening warm front lifts across the North Country today
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.
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.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 400 AM EST Monday...Low pressure system will track
Northeastward through Saint Lawrence valley today. Warm front
currently lifting across the area and light snow has begun in
Saint Lawrence county, spreading Northeastward across the rest
of the forecast area. Precipitation is still on track to reach
the Champlain valley by about 6 or 7 am. There is potential for
a messy Monday morning commute with onset of precipitation right
at commute time. Aside from snow accumulating on the roads,
visibility may also be reduced in areas of heavier snow. As
early as 10 or 11 am snow will become more upslope influenced
with the flow turning to Northwesterly. Snowfall amounts will
generally be in the 1-3" range with some isolated higher
amounts. Drivers should exercise caution this 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. Precipitation will hang on the longest across the
higher elevations, but ending everywhere overnight. Still
plenty of clouds in place though, so temperatures will not drop
too drastically. With clouds in place temperatures will not drop
very much, just about 5 degrees from daytime max temps.
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.SHORT TERM /TUESDAY THROUGH WEDNESDAY/...
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
southeast...so 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
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
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 Sunday...as 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 /09Z 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
12Z Tuesday through 06Z Wednesday...VFR/high pressure.
06Z Wednesday through 00Z Thursday...trending MVFR/IFR in
00Z Thursday onward...Mix of VFR/MVFR/IFR in periods of light