Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 162327

Area Forecast Discussion
National Weather Service Burlington VT
627 PM EST Sat Dec 16 2017

A weak upper level disturbance will move east of Vermont this
evening, allowing for clearing skies as high pressure builds in
from northern Ontario. It will be a cold night with diminishing
winds. Low temperatures are generally expected in the single
digits, and locally below zero across the northern Adirondacks.
Quiet and seasonably cold weather is expected Sunday. A weak
warm front will bring light snow late Sunday night into Monday.
Temperatures will briefly moderate above freezing on Tuesday,
before another cold front brings a return of seasonably cold
conditions mid to late in the week.


As of 626 PM EST Saturday...Previous forecast in good shape but
based on latest satellite trends did opt to update sky cover
through the overnight and early AM hours. Increasingly blocked
flow combined with lingering low level moisture behind an
exiting trough continues to produce some low level stratus
across northern Vermont with a few isolated snow showers noted
at KMVL and KEFK. Expect these clouds to persist through at
least midnight as far south as KMPV, before retreating northward
through the remainder of the night. Could impact low temps
across northern areas, but based on current readings have left
mins alone for now.

Previous Discussion...
In the wake of the trough, a nwly wind shift (10 mph with gusts
to near 20 mph next 1-3 hrs) and a reinforcing shot of arctic
air is moving in with lower dewpoints (generally in the single
digits) in the St. Lawrence Valley and points upstream across
Ontario. Will see clearing skies from WNW-ESE with dry air
advection, and as sun sets and PBL stabilizes this eve. Will see
sfc anticyclone across nrn Ontario gradually build ESEWD
overnight with diminishing NW winds as well. Should set up good
radiational cooling overnight, with lows mainly in the single
digits above zero, except below zero readings across nrn NY with
winds diminishing a bit sooner. Have gone with +7F at BTV, and
-7F at SLK.

Sunday will be seasonably cold but dry with sfc anticyclone
cresting across nrn NY and VT. PoPs NIL with highs in the upper
teens to lower 20s. Should see partly to mostly sunny

For Sunday night, a subtle warm frontal feature and weak sfc
reflection across Lake Huron will lift newd toward the North
Country. Will see increasing clouds during the night, with a
chance of light snow developing during the pre-dawn hrs across
the nrn Adirondacks into wrn VT. May see a light coating of snow
(D-0.5") in spots across nrn NY and Rutland County by sunrise,
but limited available moisture and modest forcing for ascent
should keep snowfall rates light. Temperatures will drop early
in the evening, but then level off or slowly rise later with
developing light S-SE winds. Lows Sunday night generally 5-15F,
except near zero across far nern VT with later arrival of cloud


As of 249 PM EST Saturday...Light warm air advection snow showers will
spread through the area Monday as a warm front moves northeastward
through New England. In the upper levels, confluent zonal flow
and a weakening wave moving eastward will provide some weak
synoptic ascent, however moisture will be limited and total snow
accumulations will remain under an inch from Sunday through
Monday. As the upper- level forcing departs to the east, snow
showers will generally taper off Monday afternoon into Monday
evening in valley locations and any remaining snow will become
more orographically focused. Daytime highs Monday will be
considerably warmer than Sunday, topping out in the upper 20s to
around 30 after the passage of the warm front. Monday night
temperatures will dip down a few degrees, however overnight lows
will be moderated by fairly extensive cloud cover. After
tapering off Monday evening, coverage of snow showers will once
again start to increase Monday night as the next upper- level
disturbance approaches New England from the west.


As of 249 PM EST Saturday....As a longwave trough digs over the
northeast portion of the United States, better dynamics will
support more widespread precipitation Tuesday. What will start
off Monday night as light snow showers will transition to rain
showers Tuesday morning over lower elevations of the North
Country and the Champlain Valley. By early Tuesday afternoon,
most of the forecast area will have transitioned to rain as
warmer air continues to pump in from the southwest. The upper-
level trough axis and a surface cold front will pass through New
England Tuesday night, ending the brief warm up. Colder
northwesterly flow will cool the column back below freezing and
any remaining rain showers will become all snow by early
Wednesday morning. As the more favorable dynamics clear to the
east, precipitation will become less widespread by Wednesday

Wednesday and Thursday will mark a return to cooler more seasonal
temperatures and will be considerably drier than the start of the
week, although some light snow showers can`t be ruled out as weak
disturbances pass overhead.

Attention then shifts to the potential for the next system to
approach the area towards the end of the work week/early weekend.
Models continue to spin up a surface low over the Great Lakes region
Friday supported aloft by energy ejected out of a shortwave trough
over the southwestern United States. This system is still well out
into the future and much could change over the next week.  However,
confidence is increasing that next weekend could feature fairly
active weather over the eastern portion of the country.


Through 00Z Monday...Mainly VFR conditions expected through the
next 24 hours with SCT-BKN clouds around mountain top levels
across northern Vermont to continue through the overnight hours.
Brief period of MVFR ceilings is possible at KMPV through
midnight per upstream obs at KEFK and KMVL, but beyond that all
other terminals should remain VFR. Light winds are expected
through the period as well.


Sunday Night: VFR. Slight chance SN.
Monday: Mainly MVFR, with areas VFR possible. Chance SN.
Monday Night: Mainly MVFR, with local IFR possible. Chance SHSN,
Slight chance SN.
Tuesday: Mainly MVFR, with local VFR possible. Likely SHRA,
Chance SHSN.
Tuesday Night: Mainly VFR, with areas MVFR possible. Chance SHSN,
Chance SHRA.
Wednesday: Mainly VFR, with local MVFR possible. Chance SHSN.
Wednesday Night: Mainly MVFR, with areas VFR possible. NO SIG WX.
Thursday: Mainly VFR, with areas MVFR possible. Slight chance




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