Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
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FXUS61 KBTV 040800
Area Forecast Discussion
National Weather Service Burlington VT
300 AM EST Sun Dec 4 2016
-- Changed Discussion --Cloudy skies and lingering morning flurries will give way to partial
sushine by later today as weak high pressure bridges across the
area. Weakening upper energy will then spread into the region on
Monday with widespread light snow and flurries expected. The weather
remains active as we progress through the work week with several
additional systems bringing renewed chances of light rain and
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.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --As of 250 AM EST Sunday...A rather typical early December
weather pattern continues today with plenty of cloud cover and
lingering chances of northern mountain flurries, at least
through early afternoon. Weak high pressure will be building
into the area through time, but modest northwesterly flow
combined with lingering shallow moisture trapped beneath a
persistent synoptic inversion near 850 mb should be a hindrance
to more pronounced clearing. Some afternoon sun should be
realized in the broader valleys toward mid to late afternoon
however as flow trends light. High temperatures close to blended
guidance with values in the upper 20s to lower 30s in mountain
communities, and lower to mid 30s in the broader valleys.
By tonight clouds will thin to partly cloudy in all areas for a
brief time as aforementioned surface high quickly traverses through
the area. This will be short-lived however as thickening clouds
return quickly from the south and west after midnight with approach
of a dampening upper level trough and associated vorticity
advection/warm thermal advection. Models remain generally
consistent with timing of this system with light precipitation
overspreading the southwestern half of the forecast area by
sunrise on Monday. Thermal profiles plenty cold enough such that
p-type will be all of the light snow/flurry variety with a
light accumulation of a dusting to perhaps an inch across these
areas per blended qpf/GEFS plume output. Low temperatures a bit
tricky depending on how much clearing is realized this evening
and degree to which thickening clouds put a halt on readings
later tonight, but a general idea of 15 to 20 in the mountains
and lower to mid 20s in the valleys appears reasonably close at
this point. Winds light.
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.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 335 PM EST Saturday...Upper trough will move into the
area early Monday morning and exit the area to the east Monday
evening. This is not a strong system, but dynamic forcing and
low level warm air advection will move across the area. This
will provide sufficient lift for light precipitation to move
into northern New York after midnight Sunday night and across
Vermont during the morning hours on Monday. Thermal profile
during this time period supports precipitation to be in the form
of light snow with snowfall amounts ranging from a half inch in
northeast Vermont to 1 to 2 inches elsewhere. The light snow
will begin to taper off Monday afternoon and temperatures in the
larger valleys will get into the mid 30s and this may allow for
some light rain to mix in. Dynamic support and warm air
advection moves east Monday night and precipitation should
quickly turn to light snow showers before ending around
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 246 PM EST Saturday...Large scale pattern supports
developing mid/upper level trof across the NE CONUS with several
systems expected to impact the forecast area. This will support
an increasing snow pack across the mountains...with
temperatures trending below normal by the end of the week.
Models in pretty good agreement with the strongest system with a
period of precip impacting our region Thursday into
Friday...followed by a period of backside upslope snow and low
level cold air advection. Below are some daily thoughts and
Tuesday...very quiet with building mid/upper level ridge and
1024mb surface high pres directly overhead. Forecast challenge
will be if any low level moisture is trapped below developing
thermal inversion to produce low clouds...lately this has
occurred even when soundings are dry. Will mention partly sunny
with progged 850 to 925mb thermal profiles supporting near
normal temps for early Dec...mainly upper 20s mountains to near
40f warmer valleys.
Wednesday...Both GFS/ECMWF show mid/upper level ridge breaking
down...as southern stream short wave energy and a ribbon of
enhanced 850 to 500mb moisture moves from southwest to northeast
across our region. The energy and moisture seem to be shearing
out in the confluent/fast flow aloft across the ne conus...so
only anticipating a period of mainly light snow activity. Trends
will be monitored for a stronger system with greater moisture
advection from the Gulf of Mexico...as current system is now
beginning to be sampled better. Models have been consistent
showing this system remaining unphased with northern stream
energy over the northern plains. Latest guidance shows both
850mb and 925mb temps <0C...supporting all snow...but thinking
enough boundary layer warming will occur in the Saint Lawrence
and Champlain Valleys to support a mix of rain and snow toward
18z. Dusting to several inches expected in the mountains...will
mention likely pops...but thinking impacts will be minimal.
Thursday/Friday...This period features the greatest uncertainty
as large scale pattern change occurs with modify arctic airmass
and a period of precip. Deep mid/upper level trof will be
developing across the northern plains with the coldest airmass
of the season expected to impact much of the eastern conus. As
this trof deepens potent short wave energy and associated arctic
boundary will be moving across the central great lakes and
eastern conus. GFS/CMC show short wave energy enhancing
cyclogenesis over eastern New England...which helps to develop
precip along the arctic boundary. This idea would support a
widespread accumulating snowfall for most of the area.
Meanwhile...latest 12z ECMWF shows an unphased system and no
surface low pres developing....supporting a period of rain/snow
showers with fropa. Given the expected deep trof
amplification...progged potent short wave energy...and magnitude
of cold air advection...will trend toward the higher precip
solution and mention likely pops. This scenario of a very cold
air mass interacting with very warm waters over the western
atlantic will be monitored closely...for potential greater
impacts. Stay tuned. Temps start near normal for Thursday...but
progged 850mb temps btwn -11c and -13c by 12z Friday...support
highs only in the teens mountains to upper 20s/lower 30s...with
brisk northwest winds.
Saturday...Models fall back into better agreement late Friday
into Saturday with a favorable period of accumulating upslope
snow. Deep mid/upper level trof...along with leftover 850 to
500mb moisture and favorable northwest 850mb winds of 40 to 50
knots...all point to a period of terrain driven upslope snow.
Will continue to mention likely pops in the mountains Friday
night into Saturday...with temps only in the teens mountains and
20s in the valleys for highs Saturday.
.AVIATION /08Z Sunday THROUGH Thursday/...
Through 06Z Sunday...A mix of MVFR and VFR conditions exist as
of 00z with mvfr ceilings current at MPV and SLK. There may be a
few brief periods of IFR visibilities in snow showers at both
SLK and MPV however I didn`t have the confidence to include
mention of it in the TAF`s. Persistent northwest flow and
plentiful low- mid level moisture will continue to see snow
showers in the higher terrain and along the western slopes of
the Greens. MVFR ceilings should continue to build in at all
terminals except PBG as a low level inversion looks to trap the
low level moisture through Sunday morning. At PBG expect the
downsloping wind component to help keep ceilings above MVFR
thresholds. All sites expected to return to VFR by late morning
and by mid afternoon the temp inversion may break down enough to
lead to some possible breaks in the cloud cover.
Outlook 06Z Sunday through Thursday...
06Z Sunday through 12Z Monday...Trending mainly VFR with high
pressure building into the area.
12Z Monday through 12Z Tuesday...Trending BKN/OVC VFR/MVFR cigs
with scattered areas of light rain or snow, mainly at
KMSS/KSLK. Brief IFR possible at these terminals with this
12Z Tuesday through 06Z Wednesday...VFR/high pressure.
06Z Wednesday onward...trending MVFR/IFR in rain/snow showers.