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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBTV 181229
AFDBTV

AREA FORECAST DISCUSSION
National Weather Service Burlington VT
729 AM EST Fri Jan 18 2019

.SYNOPSIS...
Scattered snow showers spread across the region today with a
coating to two inches expected. A significant snowstorm will
affect the area Saturday night and Sunday. Six to eighteen
inches of snow are expected by late Sunday, isolated higher
amounts in the Southern Greens. Bitterly cold temperatures are
then expected for Sunday night through Monday night with
dangerous wind chills.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 636 AM EST Friday...Light snow has begun to move into the
area and has generally been light so far. No big changes for 700
am update. Previous discussion follows.

Weak low pressure system passes well to our North today,
bringing scattered light snow showers to Northern New York and
Vermont. Not a lot of forcing or moisture, but could see a
coating to two inches by the end of the day. Warm southerly flow
will push temps into the upper 20s to around 30. Behind this
system, cold high pressure will briefly ridge into the area.
Temperatures drop into the single digits above and below zero
tonight. Temperatures will be cold on Saturday as well with
highs only in the single digits. Will see increase in clouds
through the day with next significant storm approaching from the
Ohio river valley. Snow will begin during the evening hours,
spreading from southwest to northeast across the area.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/...
As of 323 AM EST Friday......WINTER STORM WARNINGS AND ADVISORIES IN
EFFECT...

Very little change made to the forecast from previous thinking for
the weekend storm as 00Z NWP remained very consistent with the
previous runs with the only notable change being a slight change in
timing. With that in mind, confidence is now high enough to warrant
winter storm headlines for Saturday night through Sunday.

Borrowing from my discussion yesterday to describe the synoptic
setup, energy dropping into the four corners early this morning
remains progged to lead to lee side surface cyclogenesis later this
afternoon over the southern Plains. Meanwhile, strong arctic high
pressure located near Hudson Bay will be providing the Northeast
with a bitter cold and dry airmass Friday night into Saturday with
925mb temps in the -15C to -25C range. This will set the stage for a
strong thermal gradient to develop across the Tennessee Valley where
the developing surface low will track east-northeast to near D.C by
Sunday morning, and further on over Cape Cod and into the Bay of
Fundy by Sunday night. Snow spreads into the forecast area from
southwest to northeast Saturday evening, with the worst travel
conditions expected early Sunday morning from roughly 06-15Z with 1-
2"/hr snowfall rates possible, especially across central/southern
Vermont where an enhanced band of 850mb fgen is progged to pivot. A
change from previous model runs is that by 18Z the best deep layer
moisture and lift begin to quickly lift east-northeast away from the
region so expect snow to rapidly taper off towards sunset instead of
later into the evening.

Now that we`re entering time range of mesoscale models we`re able to
begin to provide better detail to the expected QPF and subsequent
snowfall accumulations which based on mean SLR`s of 15-20:1 will
yield a wide area of 12+ inches. Thinking the St. Lawrence Valley
sees the least amount of snowfall due to drier northeasterly flow
and being further removed from the surface low on the coast with
accumulations mainly in the 6-8" range. The Adirondacks to the
Champlain Valley should see 10-14", 12-16" central/northeast VT, and
the big winners will be southern VT where Rutland/Windsor/Orange
counties see 16-20" with locally up to 2 feet possible across the
higher terrain.

An additional hazard during the storm will also be increasing
northerly winds during the daylight hours Sunday, with areas of
blowing snow likely. North winds of 15-25 mph, with gusts to 35 mph
are likely in the Champlain Valley, resulting in low visibility in
blowing snow at times.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 323 AM EST Friday...Bitterly cold wind chills continue to be
main highlight for the long term as a strong pressure gradient
develops over the region Sunday night through Monday as departing
low pressure deepens across the Canadian Maritimes, and arctic high
pressure builds into the Northeast. Strong low level cold air
advection noted by 925mb temps dropping into the -25 to -30C range
combined with northerly winds of 15-25 mph will yield wind chills of
20 to 30 below, and locally as low as 35 below across the Northern
Adirondacks Sunday night. Temperatures don`t budge out of the single
digits above and below zero either Monday despite winds beginning to
abate as high pressure will center overhead Monday night. Wind chill
warnings and advisories look probable, but we will address this
later on down the road.

High pressure builds over region for Monday night through Tuesday
with continued arctic temps of -5F to -20F for lows Monday night,
but light southerly return flow Tuesday will offer highs warming
into the teens above zero. Our next system approaches Tuesday night
with a drastic change in temps possible as surface low pressure
looks to track northeast through the St. Lawrence Valley ushering in
a much warmer airmass. So much warmer than ptype will be an issue as
highs surge into the 30s Wednesday with a mix of rain and snow
possible through Wednesday night before a cold front passage early
Thursday morning.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
Through 12Z Saturday...1500 to 2500 foot overcast deck has
overspread the North Country. Snow showers are expected to move
across the region today which will create some localized IFR
visibilities at MSS and SLK. Other locations may see brief
periods of IFR/MVFR visibilities with snow showers but MSS and
SLK are the most likely locations to see snow showers through
Friday afternoon. Winds have shifted to the south 5 to 12
knots. It looks like ceilings will improve and snow showers will
exit the region after 18Z Friday but lingering MVFR ceilings
will be seen across northern New York and southern Vermont.
Ceilings will continue to improve to VFR overnight.

Outlook...

Saturday: VFR. Chance SN.
Saturday Night: Mainly MVFR and IFR, with areas VFR possible.
Definite SN.
Sunday: Mainly MVFR and IFR, with areas VFR possible. Definite
SN, Chance SHSN, Areas BS.
Sunday Night: VFR. Chance SHSN.
Martin Luther King Jr Day: VFR. Slight chance SHSN.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. Slight chance SHSN.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Winter Storm Warning from 4 PM Saturday to 4 PM EST Sunday for
     VTZ001>012-016>019.
NY...Winter Storm Warning from 4 PM Saturday to 4 PM EST Sunday for
     NYZ028>031-034-035.
     Winter Weather Advisory from 4 PM Saturday to 4 PM EST Sunday
     for NYZ026-027-087.

&&

$$
SYNOPSIS...Neiles
NEAR TERM...Neiles
SHORT TERM...Lahiff
LONG TERM...Lahiff
AVIATION...Neiles