Area Forecast Discussion
Issued by NWS Burlington, VT-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KBTV 070011
Area Forecast Discussion
National Weather Service Burlington VT
711 PM EST Tue Dec 6 2016
A weak weather system will bring another round of light snow
tonight and Wednesday morning to the region. Light accumulations
are expected, which will lead to some slippery travel
conditions. Additional snow showers are in the forecast for
Thursday into Friday as colder air begins to moves in to the
region. Significant snow accumulations are possible in parts of
northern New York. The weekend is expected to be seasonably cold
with scattered snow showers each day.
.NEAR TERM /THROUGH WEDNESDAY/...
-- Changed Discussion --As of 644 PM EST Tuesday...Mid-upper clouds are rapidly
overspreading the North Country this evening from SW to NE in
advance of shortwave trough across the upper Ohio Valley. Won`t
see much cooling overnight as a result, with low temperatures
near current values in the upr 20s to near 30F.
Primary weather maker for the next 24 hours will be a burst of
light precipitation associated with warm advection and a weak
upper level trough. Composite mosaic radar reflectivity shows
the leading edge of this precipitation extending from near KROC
to KBGM at 2345Z. Current trends suggest snow will reach the
Northern Adirondacks of NY around 05-06Z, and into the
Burlington area by 08-09Z...consistent with previous shift
expectations. All the hi-res models agree that as the
precipitation shield lifts towards us, the intensity will be
decreasing and starting to fall apart. this is best seen in the
various "forecast radar" outputs. Total liquid precipitation is
not expected to be all that much. Roughly 0.05-0.15" (highest
totals south). It`s a "high PoP, low QPF" event.
Profiles all suggest temperatures aloft will be cold enough for
snow. Snow-liquid ratios will be running 9-12:1 or so. That
suggests total snowfall will be 1/2" to just under 2" or so. As
the night goes on, a low level southerly jet develops. This
should help to reduce the overall amount of precipitation across
the Champlain Valley. Though accumulations will be on the light
side, timing suggests some slick spots for the morning commute.
Temps generally rise above freezing by mid-morning, so localized
issues with snow/icy spots will abate later in the morning.
Precipitation tapers off quickly in the morning. Some of the
snow may end as a little bit of sprinkles of rain or drizzle as
the moisture depth decreases and we start to lose the ice
formation ability within the clouds. Generally cloudy skies will
Highs tomorrow should be a few degrees above normal, topping out
well into the 30s and perhaps even close to 40.
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.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
As of 338 PM EST Tuesday...Primary feature influencing the
North Country`s weather for the short term period will a strong
mid/upper level trough swinging through the Great Lakes
Wednesday night, and the northeast states Thursday through
Thursday night. While little widespread/synoptic precipitation
is expected, cold air advection behind a departing surface front
combined with increasing southwesterly flow and warm Lake
Ontario waters will aid in the development of a lake effect snow
band early Thursday morning across portions of southern St.
Lawrence and southern Franklin counties of Vermont. In addition,
snow is expected to reach further downwind into northern
Vermont, specifically around the Jay Peak region as the 850mb
flow should be strong enough to support the transport of
moisture there and will be enhanced by upslope processes. As the
base of the upper trough swings across the BTV CWA Thursday,
snow showers will become more widespread outside of the deeper
valleys and likely a bit more convective as guidance is showing
a little bit of CAPE, upwards of 100 J/kg across the higher
Overall QPF for the event over a 24hr period from midnight
Thursday to midnight Friday is less than a tenth for the
valleys, but upwards of close to a half inch in the heart of the
lake effect band and the northern Greens around Jay Peak. First
guess at snow ratios puts us around 15:1 on average, yielding
around 6-9" across southeastern St. Lawrence County prompting
the issuance of a Lake Effect Snow Watch there. Across the rest
of the area a dusting to and inch in the valleys is possible
where snow may briefly mix with rain due to warm boundary layer
temps, while portions of north-central and northeast Vermont
could see 2-4" and the highest summits from Mount Mansfield to
Jay Peak upwards of 4-6".
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 338 PM EST Tuesday...Overall the outlook for the end of
the week and through much the upcoming weekend is a fairly good
one with snow showers becoming more scattered through the day on
Friday, and high pressure building in over the eastern seaboard
for Saturday and Sunday. Upper flow remains out of the
west/northwest so unfortunately we`ll likely see more clouds
than sun with temps seasonably cool in the 20s for highs and
teens to single digits for lows.
Next potential system rolls into the area Sunday night, but
exactly where the low tracks is still very much in question with
global models in disagreement on the depth and strength of an
upper trough shifting out of the central CONUS. Currently
offering a blended approach with high chances for mainly snow
Sunday night through Monday night, but that will certainly
change as we dial in the forecast over the next couple of days.
.AVIATION /00Z Wednesday THROUGH Sunday/...
-- Changed Discussion --Through 00Z Thursday...Low clouds have generally dissipated
early this evening, except for lingering MVFR at PBG with
ceiling heights around 2000ft. Should see VFR with increasing
mid-upper level clouds thru 04Z. Somewhere between 04-07z
expecting light snow to develop from southwest to northeast. As
this happens, we`ll see IFR conditions develop, mainly due to
1-2SM vsby in snow. Some impact expected to airport ground ops
for morning pushback due to light snow accumulations.
Snow will start to break up into more showery conditions after
14z Wednesday. Generally went with "VCSH" in the TAFs, but will
see lingering MVFR ceilings for most locations with HIR TRRN
OBSCD. South winds may gust 15-20kts in the Champlain Valley
after late morning thru afternoon.
Outlook 00Z Thursday through Sunday...
Entire period - frequent MVFR ceilings. Scattered snow showers
each day, resulting in localized IFR visibility and ceilings.
Maybe extended period of IFR for SLK Wednesday night into
Thursday night with frequent snow showers in that area.
-- End Changed Discussion --
NY...Lake Effect Snow Watch from late Wednesday night through
Thursday evening for NYZ029.