721
FXUS61 KBTV 141138
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
638 AM EST Wed Nov 14 2018

.SYNOPSIS...
High pressure will build into the region today with clearing skies
and slowly decreasing winds. Temperatures will be on the chilly side
with highs mainly in the teens to mid 20s. Tonight will feature
clear skies and light winds, which combined with some snow pack in
the higher terrain will result in lows ranging from near zero to the
mid teens near the warmer Lake Champlain water. A dry day is
expected on Thursday, before another coastal system impacts our
region Thursday night into Friday. A widespread plowable type
snowfall is possible with temperatures warming back into the 20s and
30s.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 509 AM EST Wednesday...Have update the forecast to expand
chc pops across most of the dacks and the central/northern
mountains of VT. What a wonderful problem to have in mid Nov,
which is trying to find the off switch to the snow machine,
light snow showers have been falling all night at slk. Little
rusty in my identification of what is causing this precip, but
combination of water vapor and ir satl tells the story. Weak
lift from channeled vorticity is interacting with upstream lake
enhancement moisture, along with strong caa is aiding in
squeezing out the remaining moisture in favorable upslope flow,
to produce narrow bands of light snow shower activity across
northern NY into VT. Web cams indicate some light snow
accumulation overnight, so have also bumped snowfall amounts up
to a dusting to 0.5. Not a big deal overall, but thought an
update was needed to capture the latest trends. This activity
should decrease in areal coverage/intensity by 15z this morning.

Coldest airmass of the season is currently across the North
Country as 00z Maniwaki indicated 850mb temp of -19c, which is
very impressive for this time of year. Water vapor continues to
show a complex upper level pattern across the conus with
mid/upper trof over the ne conus, while energy and moisture
increases over the se conus, ahead of our next system Thurs
Night into Friday. For the near term, our weather will be
influenced by building 1036mb high pres from central Great
Lakes. The pres difference btwn building high pres and departing
low pres will continue to produce brisk northwest winds 15 to
30 mph across our fa today, which will decrease by mid to late
aftn. These upslope winds, combined with weak 5h vort have
produced some light snow shower activity early this morning,
which will dry up by 15z. Maybe a dusting in the dacks/mountains
of Vt.

Near record lows anticipated tonight with mainly clear skies away
from Lake Champlain as high pres builds directly overhead. This
combined with light trrn driven winds and some fresh snow pack,
expect lows from -5f coldest valleys in the nek/slk to lower/mid
teens cpv. See climate section below for records. METSLK has -12f
which is impressive, but thinking closer to the warmer MAV/ECE
values. Soundings show extreme instability associated with lake temp
near 9c, while 850mb temp is -15c to -18c, this instability,
combined with lighter cloud layer winds should allow greater parcel
time over the water to produce a few lake effect clouds downstream
of Lake Champlain this aftn/evening. Flow becomes light tonight, so
more of a tea kettle effect anticipated as warm air rises, it cools
by expansion, and should be enough to produce some localized clouds
near the Lake.

Thursday after a chilly start mid/upper level moisture begins to
overspread the region aft 18z. Expect clouds to lower and thicken
during the afternoon hours with temps mainly in the mid 20s to mid
30s. Light winds become south/southeast 5 to 15 mph.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 400 AM EST Wednesday...Our next significant winter system
will be moving into the North Country during the overnight
hours. Bottom line up front -> Looks like widespread 4-7 inches
of more wet snow with ratios between 10-11:1.

Thursday night the closed upper level low will be over southern
Appalachia and will be digging to the north and east. A weak
surface low will develop off the Mid-Atlantic coast and will
start to push precip into New England. There`s pretty good lift
and decent dynamics that will mean everywhere should see
significant wintry precip with the eastern slopes seeing the
highest totals due to orographic enhancement.

The challenges right now are how far does the warm nose push
in, and similarly where does the dry slot move in. The
consensus of guidance is that there will be a dry slot that gets
wrapped in as the low deepens on Friday but there`s quite a
spread in where. So pinning those two features down ended up
being quite the difficult forecast. As the precip pushes in
Friday night expect the column to be cold enough everywhere for
all snow until early Friday morning. Thats when the warm air
aloft will start to push in across southern New England along
with a loss of RH in the DGZ. So I`ve added a buffer of some
freezing drizzle into the forecast over Southern Vermont where
we have the best chance of losing cloud ice.

The 00z suite of guidance came in quite a bit heavier in terms
of qpf but I wasn`t quite ready to go all in with the higher
totals so I just trended slightly higher qpf. With snow ratios
in the 10-11:1 range as the snow first pushes in I could see
3-7 inches of snow from midnight to noonish and then the low
will start to shear away from the region turning the snow from
stratiform to more showery. When that happens expect northwest
flow to move in and the western slopes will start to see
enhanced snowfall at rates more close to climo in the 13-15:1
range. At the end of the day Friday anticipate a nice layer of
fresh snow across the entire North Country. With the low pushing
towards Nova Scotia Friday afternoon the mid level flow and
cold air over the warm Great Lakes should generate a lake
response in the form of some lake effect snow. Lake induced CAPE
values push into the 200-300 J/kg range which with light shear
should be enough to see some minor accumulations in southern
Saint Lawrence county.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 400 AM EST Wednesday...High pressure will be building in
at the surface on Saturday with some lake effect snow
continuing east of Lake Ontario. Cold air advection will be
pushing into the region and we`ll see temps falling Sunday into
Monday below normal with highs in the 40s Saturday and in the
upper 20s to near freezing for Sunday and Monday. Tuesday looks
pretty brutal with a deepening low pressure system over
Newfoundland which pushes a lobe of the polar vortex into
Quebec. Both the GFS and EC show this feature but the GFS is
much colder bringing some -20C 850mb temps to the North
Country. Both deterministic models bring some single digits
highs to the North Country. We`ll continue to monitor that but
its definitely worth noting that a pretty cold airmass looks on
its way next week. Precip chances will generally stay in the
chance category throughout the weekend into mid week as we`ll
see several open short waves track through the North Country
with the most defined wave tracking through sometime Monday
afternoon into Tuesday morning.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
Through 12Z Thursday...Periods of mvfr cigs/vis possible
through 15z as upslope flow and low level cold air advection
combined to produce mountain clouds and light snow shower
activity. Moisture profiles quickly decrease by this aftn with
mianly vfr conditions prevailing. Brief 15 to 20 minutes of ifr
cig/vis is possible this morning at slk, as upstream obs at
OGS/PTD show ifr cigs. Winds will become breezy from the
northwest at 10 to 15 knots with localized gusts up to 25 knots
possible. These winds will decrease and become trrn driven by
sunset with vfr conditions prevailing overnight.

Outlook...

Thursday: VFR. NO SIG WX.
Thursday Night: Mainly VFR, with areas MVFR and IFR possible.
Definite SN, Chance FZDZ.
Friday: MVFR and IFR. Likely SN, Definite RA, Chance FZDZ.
Friday Night: Mainly MVFR, with local VFR possible. Chance SHSN.
Saturday: Mainly MVFR, with areas VFR possible. Chance SHSN,
Slight chance SHRA.
Saturday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHSN.
Sunday: VFR. NO SIG WX.

&&

.MARINE...
A Lake Wind Advisory continues today for west/northwest winds 15
to 25 knots with localized gusts up to 30 knots. These winds
will decrease to 10 to 20 knots toward sunset. Waves generally 1
to 3 feet, except some higher swells in the open water.

&&

.CLIMATE...
Below are the record low min temperatures for November 15th:

Burlington, VT      9 (1933)
Montpelier, VT      8 (1996)
St. Johnsbury, VT  16 (2003)
Massena, NY        12 (1967)
Plattsburgh, NY    13 (1967)
Saranac Lake, NY  -12 (1993)

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Taber
NEAR TERM...Taber
SHORT TERM...Deal
LONG TERM...Deal
AVIATION...Taber
MARINE...
CLIMATE...RSD