Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 250749

Area Forecast Discussion
National Weather Service Burlington VT
349 AM EDT Tue Oct 25 2016

A trough of low pressure will continue to produce brisk winds and
chilly temperatures through midweek with scattered mainly mountains
snow showers. Temperatures will be in the 30s mountains to lower 40s
valleys today and Wednesday. A widespread precipitation event is
expected on Thursday into Friday with some snow accumulation likely
in the mountains and breezy southeast winds along the western


As of 347 AM EDT Tuesday...Water vapor shows deep cyclonic flow
associated with mid/upper level trof across the northeast
CONUS...with sharp moisture gradient from very dry air central NY
to some mid level moisture northern New England. The combination
of this moisture...with favorable upslope flow will produce mainly
mountain focus snow showers today. So far activity has been very
limited due to the very dry low levels and lack of upper level
support. Thinking as weak embedded vort in the flow aloft drops
across our northern cwa between 15z-20z today and interacts with
some instability from surface heating...scattered valley rain and
mountain snow showers will develop.

Hi resolution composite reflectivity progs show popcorn nature to
returns...with greatest concentration over the northern mountains.
Will continue to mention likely pops northern green mountains from
Mansfield to Jay Peak with a dusting to several inches possible.
Elsewhere...will mention slight to chance pops...with some
enhancement possible on the east side of Lake Champlain associated
with lake effect. Would not be surprised to see a few wet snow
flakes in the valley....given the chilly 925mb to 850mb thermal
profiles. Models in good agreement of values between -7c and -9c
today at 850mb and -1c to -3c at 925mb...these temps support highs
low/mid 30s mountain towns and upper 30s/lower 40s warmer valleys.
Still expecting breeze northwest winds at 10 to 20 knots with some
locally higher gusts especially midday.

Tonight...areal coverage of any leftover precip will dissipate by drier air at all levels develops across our region. Will
mention chance pops mainly in the mountains...and will still need to
watch the potential for some lake effect clouds and flurries on east
side of champlain overnight. Temps will cool into the lower/mid 20s
mountains to lower/mid 30s valleys.


As of 332 PM EDT Monday...The upper level trough will slowly drift
towards the east as persistent cold air advection continues to
provide below normal temps in the short term through the mid week.
The continued northwest flow aloft will cause some light upslope
snowfall. The flow will be unblock so areas with the highest
accumulations will be in the western upslope locations such as
Underhill, Jericho, Bolton etc. However with total qpf will be
less than 0.10 which ultimately means we`ll only see an inch or
two of snow fall.

Wednesday we will be in sort of a lull between two systems. Expect
cloudy conditions in the higher terrain with some breaks in the
cloud cover in the Saint Lawrence and Champlain Valleys. The low
and mid level moisture will be decreasing and so while the
orographic forcing is still favourable for snow I dont anticipate
much in the way of accumulation along the ridgeline Wednesday. The
cold air advection even as a weak ridge starts to build in. Expect
max temps to remain below normal as the entire column of air above
925mb is below 0C. Highs will be in the upper 30s to around 40 in
the valleys.


As of 425 PM EDT Monday...By Thursday the pattern picks up again
with several chances for rain and snow. The upper level trough
builds back in thus the upper level flow will remain west to
northwest through the end of the week and into the weekend.

The first surface low pressure system will track through the Great
Lakes into New England on Thursday night and should bring quite a
bit of warm advection to the area. The rain vs snow forecast will
be quite tricky as the overnight temps will be supportive of snow
however the warm air advection will be advancing rapidly with a
southerly 850mb jet of 40-50kts bringing warmth from the Atlantic
west of the spine of the Green mountains. However on the eastern
side of the Greens the cold air will be trapped longer due to the
high pressure system located over Nova Scotia. So I anticipate
precip beginning first as snow across the entire area however by
mid morning on Friday that will transition to a mix of rain and
snow except for areas east of the Green mountains. Temp profiles
in the higher terrain suggest they will stay all snow.

The bigger issue will be the potential for gusty downslope winds.
The track of the low pressure system will be critical as if the
GFS is correct the low tracks across the CT/MA/NY border and the
winds will be due east over the southern Green mountains. However
the EC is slightly further north and thus the strongest winds
dont turn east until the system is already east of the forecast
area. If the GFS is correct there will be a 35-45kt 850m easterly
jet over the southern Greens which would be supportive of
downslope gusty winds. We will need to continue to monitor that
as the forecast becomes clearer.

Next system arrives late Saturday into Sunday with additional
chances for precipitation however most of the guidance is warm
enough that the system will produce mainly just rainfall. Based on
GFS and EC soundings the entire column below 850mb is positive so
based on the 12z suite of guidance I anticipate rain and max temps
in the mid to upper 40s and lows in the 20s to mid/upper 30s.


.AVIATION /08Z Tuesday THROUGH Saturday/...
Through 06z Wednesday...Mainly vfr conditions with occasional mvfr
possible at mpv/slk this morning associated with lowering cigs and
chances for mountain snow showers. The limited moisture both at
the surface and aloft will limit impacts on tafs with regards to
vis/cigs. Otherwise...still expecting breeze west to northwest
winds 10 to 20 knots with a few higher gusts through
today...before decreasing around sunset this evening at 4 to 8

Outlook 06z Wednesday through Saturday...
Active weather pattern continues with vfr trending toward mvfr/ifr
Thursday into Friday. Expecting a period of snow at most sites on
Thursday afternoon...with vis between 1-3sm...before changing to
rain in the valleys by evening. Also...gusty southeast winds are
possible...especially at rutland...creating areas of low level
wind shear and turbulence. As winds shift to the northwest on
Friday...ifr cigs are possible at BTV/RUT/SLK/MPV with areas of
scattered rain or snow showers. Next system arrives late Saturday
with additional precipitation and breezy southwest winds.
Occasional mvfr/ifr conditions are likely by late Saturday.




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