Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 270523

Area Forecast Discussion
National Weather Service Burlington VT
123 AM EDT Thu Oct 27 2016

Partial clearing and light winds are expected tonight as high
pressure briefly settles over North Country. This will lead to
chilly temperatures tonight, with lows generally in the 20s. The
next low pressure system will approach from the Great Lakes later
Thursday, with the primary low tracking into the St. Lawrence
Valley before a secondary low takes over closer to the New England
coast during Thursday night. After increasing cloudiness Thursday
morning, looking for precipitation to develop Thursday afternoon
and continue through Thursday night into Friday morning. After a
brief rain/snow mix, precipitation will be predominantly rain at
elevations below 2000 feet. Several inches of wet snow
accumulation is possible at the higher summits. Total rainfall
amounts generally a half inch to one inch, highest along the
eastern slopes of the Adirondacks and Green Mountains.


As of 109 AM EDT Thursday...Overall forecast in great shape early
this morning with only a few minor tweaks to clouds and both
hourly and expected low temps. The combination of departing mid
level clouds from days of cyclonic flow and approaching high
clouds from next system will result in mostly cloudy skies
overnight. These clouds will tend to keep temps several degrees
higher...with lows mainly near 20f slk/northeast kingdom valleys
to lower 30s near lake champlain.

Previous discussion...Mostly cloudy to cloudy conditions persist
in NW flow, with lingering inversion near 5kft (per RAP soundings)
helping to trap moisture and stratocu layer. Sfc ridge axis across
sern Ontario will gradually shift ewd this evening into tonight.
Effect will be for winds to become light and variable, and should
see some partial clearing during after sunset. Depending on amount
of clearing and radiational cooling, should be a chilly night.
Certainly lows in the 20s for most sections. If skies can become
mostly clear, may see a few readings in the teens for the nrn
Adirondacks. Other than a lingering flurry across n-central into
nern VT late this aftn, expecting dry conditions overnight.

Dry conditions will be short-lived as next wave of low pressure
approaches from the Great Lakes region on Thursday. Surface low
will shift across Lake Erie/nwrn PA late Thursday morning, with
increasing mid-upr clouds across our area. Leading surge of
850-700mb warm advection and associated precipitation arrives
around 18Z across s-central VT and into the Adirondacks of NY.
Precipitation will overspread the remainder of the North Country
late in the afternoon...early evening for far nern VT. In terms of
precipitation type, PBL will have a chance to warm out ahead of
the arriving precipitation, generally into the low 40s.
Anticipate some wet-bulb cooling with precip onset as column
saturates, allowing for wet snowflakes as low as 500ft elevation
mid- afternoon Thursday, but thereafter, looking at mainly a rain
event below 1500ft with continued WAA and strengthening S-SE
flow. Generally no snow accumulation at all below 1500 ft. May see
a slushy coating to an inch 1500-2500ft. Above 2500ft, temps will
hold on below freezing longer, and could see 4-8" across the
highest summits of nrn NY and central/nrn VT through Thursday
night. With a 50-kt sly low-level jet, there is a warm (above
freezing) layer that comes in above summit level, so may see some
periods of sleet as well into Thursday night. So, not expecting
any impact for population/roadways, but the highest summits could
see a moderate accumulation of wet snow based on current trends.
Highs on Thursday generally in the low-mid 40s, and near freezing
across the highest summits of VT and nrn NY.

One other issue will be moderate winds on the western slopes of
the Green Mtns, and across all of the higher terrain. SE winds
peak during Thursday evening, and should see 15-25 mph with a few
gusts 30-35mph possible along the immediate western slopes, as
primary surface low tracks into the St. Lawrence Valley. Later
Thursday night, gradient slackens as secondary low development
takes place across sern new England...and should see sfc winds
weaken. Stable low-level conditions will limit areal coverage of
gusty winds to the immediate wrn slopes. Winds at summit level
could reach 50mph consistent with model soundings closer to

In terms of total QPF, looking for some precipitation enhancement
along the ern slopes of the Greens and into the ern slopes of the
Adirondacks given low-level sely (upslope) conditions. Total
rainfall amts ranging from 0.6" across the St. Lawrence and
Champlain Valleys, but locally around 1" in aforementioned upslope
flow areas, from Ludlow up to Bethel, and across portions of
Essex/Clinton Counties in NY.


As of 328 PM EDT Wednesday...The potential low pressure system
will be losing energy Friday morning as a shortwave vorticity
maxima pushed the center of the low south and east from the Saint
Lawrence to off the coast of New Hampshire. As this happens the
warm air will continue to surge north and generally rain will be
falling over the North Country except for a few higher elevation
sites over the Adirondacks and northern edge of the spine of the

By mid day northwest flow develops and there will still be some
low level moisture at 925mb rh still exceeds 98% however moisture
in the snow growth zone will be minimal so any snow/flurries will
be confined to the areas with orographic lift. Friday should only
see 0.10-0.20" of qpf across the eastern Vermont zones mainly
falling as rain with a couple of hundredths of qpf across the rest
of the north country. Snow totals will really be continued to
elevations 2500-3000 feet and above and should only amount to an
inch or two of additional accumulation of heavy wet on Friday
adding to the 4-8 already from Thursday.


As of 357 PM EDT Wednesday...To start the weekend we will be
under marginal warm air advection on Saturday. A ridge of high
pressure will be slowly moving east in and 850 temps warm to +6C -
+8C. Clouds will be increasing and thickening as a weak northern
stream low tracks well to the north of the forecast area. With
boundary layer temps warm and little cold air to speak of it will
be just a typical late October rain event. QPF totals will be on
the lower side but most of the area should see some light rain

Behind that low, a eastern conus ridge builds in and leads to dry
air through the mid week before another low pressure system tracks
just north of the Great Lakes and brings an additional chance for
showers to start November.


.AVIATION /06Z Thursday THROUGH Monday/...
Through 06z Friday...Several impacts to aviation expected over the
next 24 hours associated with approaching storm system. Vfr
conditions will prevail through 15z Thursday...with precip and
mvfr cigs developing at MSS/SLK/RUT by 18z...with a period of wet
snow providing intervals of ifr vis at slk. The precip overspreads
PBG/BTV and MPV by 20z with mvfr cigs and potential brief period
of ifr vis at MPV in -sn. Expecting mainly a cold rain by 00z at
all taf sites with mvfr cigs...some ifr cigs are possible at MSS
associated with northeast flow and MPV/SLK. Next concern is
developing low level jet of 45 to 55 knots at 5000 feet lifting
from southwest to northeast across our taf sites between 00z and
06z. This will create areas of turbulence and enhanced low level
wind shear...especially when this jet interacts with the higher
terrain. A few surface gusts between 30 and 35 knots can be
expected at RUT between 00z-06z Friday with gusts up to 30 knots
possible at BTV.

Outlook 06z Friday through Monday...
Precip will be slowly ending from southwest to northeast by 12z
Friday with lingering upslope focused precip impacting mpv/slk.
Profiles support mostly rain. As winds shift to the northwest on
Friday morning...intervals of ifr cigs are possible at
BTV/RUT/MPV/SLK...given the amounts of low level moisture
available. A warm front feature lifting across our taf sites on
Saturday morning will shift the winds to the southwest with some
scattered showers possible...especially mss/slk. Expecting mainly
vfr conditions with intervals of mvfr cigs possible across
northern NY taf sites on Saturday. Gusty southwest up to 35 knots
are possible at MSS with 30 knots expected at SLK/BTV on Saturday.
Another wind shift to the west/northwest will occur Sat Night into
Sunday with additional scattered showers. Drier conditions with vfr
flight conditions for Sunday afternoon into Monday.




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