FXUS61 KBTV 180854

Area Forecast Discussion
National Weather Service Burlington VT
354 AM EST Mon Dec 18 2017

A warm front approaching from southwestern New York will bring
increasing cloudiness and widespread light snow this morning into
the afternoon. Snow accumulations between 1 and 3 inches are
generally expected, with localized totals around 4 inches for the
southern Green Mountains. A brief warm up is expected on Tuesday,
with gusty south to southwest winds. A frontal passage Tuesday
evening will bring a few rain or snow showers and a return to colder
temperatures. The next chance for significant precipitation will
arrive Friday night into Saturday. A low pressure system passing to
the west of the region is expected to bring mixed wintry
precipitation, transitioning to plain rain as warmer air moves in on
south winds.


A warm front, currently stretching from eastern Lake Erie
across northern PA/NJ, will slowly shift northward through
Tuesday. Already seeing light warm advection precipitation over
southern and western sections of our CWA, and this will continue
to spread over the remainder of the area this morning. Although
today will be warmer than yesterday, temperatures will remain
cold enough for this precipitation to fall as snow, which should
become more focused across the mountains as we head into the
afternoon. The snow will taper to showers later this evening as
weak low pressure slides to our north, ushering in some drier
air aloft. Low levels will remain relatively moist however; thus
expect some patchy freezing drizzle to develop overnight and
persist into early Tuesday morning. Continuing warm advection
tonight means temperatures will hold fairly steady or rise a bit
overnight, though they will remain cold enough for snow.
Snowfall totals through tonight will be in the 1 to 3 inch
range, with isolated higher amounts across the higher terrain of
the southern Greens.

Warm advection surges on Tuesday as the warm front moves to our
north, allowing showers to spread over the region once again.
Although the precip will start out as snow, temperatures rising into
the mid 30s to around 40 will allow the snow to change over to rain
in most locations. Higher elevations will likely remain a rain/snow
mix. The showers will become most numerous in the afternoon as a
cold front approaches from the north. Any snow accumulation will be
an inch or less.


As of 316 AM EST Monday...Large scale pattern shows developing
mid/upper level trof with weak sfc boundary passing across our
fa. The combination of caa...upslope flow...good 5h energy...and
some leftover moisture will result in a period of accumulating
snowfall across the dacks/green mountains Tues Night into Weds.
925mb temps near 0c at 00z Weds...support mainly rain valleys
with snow levels btwn 1500-2000 feet...but quickly dropping to
the valley floors by 06z Weds...as 925mb temps cool. Have
mention likely to cat pops from northern Dacks into the
central/northern Green mountains for Tues Night into Weds
Morning...with 3 to 5 inches of snow accumulation possible.
Meanwhile...westerly flow and warm boundary layer temps will
limit accumulation across the cpv and ct river valleys to an
inch or less. Have kept pops in the schc/chc range. 1030mb
surface high pres builds into our cwa on Weds into Weds
night...with west/northwest flow continuing. This results in
deep layer drying...along with progged 850mb temps dropping
btwn -14c and -16c by 12z Thursday. These thermal profiles
suggest steady or falling temps on Weds...under brisk winds.
Thinking lows mainly mid 20s to lower 30s by Weds AM...with
highs mainly in the 20s to lower 30s Weds...before dropping
into the single digits above and below zero. Still some question
on snow pack and winds...so have stayed close to
guidance...which has been too warm lately with lows in the
deeper protected valleys.


As of 316 AM EST Monday....1030mb high pres provides cwa with a
chilly but dry day on Thursday...with progged 850mb around -15c.
Highs mid teens to lower 20s with light northwest winds.
Thursday Night...temps will be tricky as latest 00z ECMWF shows
850 to 500mb moisture streaming from west to east across our
fa...along with increasing winds aft 06z Friday. Thinking temps
fall quickly early Thurs evening...before increasing aft
06z...with clouds/winds developing. Lows ranging from -5 to -10f
NEK/SLK to 5 to 10f cpv/slv. If skies are clear and winds stay
light...these temps will be much colder.

Next large scale synoptic system will impact our cwa Friday into
Saturday...as mid/upper lvl trof deepens across the central
Plains and sfc low pres develops. Models in good agreement with
sfc low pres tracking across the MS Valley into the central
Great Lakes by 12z Saturday...placing our cwa well established
in the warm sector. However...1030mb high pres over northern ME
will produce the classic cold air damming signature with cold
air remaining locked in the deeper valleys of eastern/central VT
late Friday into Saturday...even with progged 850mb temps
warming to 6c. Latest trends show a series of warm fronts and
associated ribbons of enhanced 850 to 700mb lift/moisture
impacting our cwa. Initially thermal profiles support all snow
late Friday aftn/evening with first surge...however developing
southwest 850mb jet of 55 to 65 knots will quickly warm 925mb to
850mb layer above 0c by 12z Sat. Meanwhile...cold air will
remain trapped in the northern SLV and parts of central/eastern
VT...especially ct river valley/nek with areas of sleet/freezing
rain likely. An advisory level event with some ice accumulation
looks likely at this time...given available moisture/lift. QPF
with southwest orientation of llvl jet will be terrain
influenced...with typical shadowing here in the cpv off the high
peaks. Difficult to determine amount of low level mixing with
shallow inversion and potential for gusty winds at this time.
Highs Saturday will range from the mid/upper 30s colder valleys
of eastern VT to lower/mid 50s CPV/parts of the western
dacks...thinking all locations briefly break into warm sector
with better mixing prior to fropa late Saturday into Sunday.
Sharp boundary sweeps across our fa with a period of rain
showers...changing to mountains snow showers by 12z Sunday.
Limited accumulation with developing dry slot behind fropa.
Temps mainly in the upper 20s to mid/upper 30s on Sunday with a
few leftover mountain snow showers possible.


Through 06Z Tuesday...VFR conditions will exist through about
09z with only mid and high level clouds over the area.
Eventually after 09z a warm front will approach from the
southwest and ceilings will lower into the MVFR category with
light snow developing as well. The snow will reduce visibilities
into the MVFR and IFR categories between 12z and 18z...then
improve back into the VFR category for the remainder of the
period. Ceilings however will remain in the MVFR category for
the remainder of the period, lowering to IFR at SLK late. Winds
will generally be variable and under 10 knots through about 18z
before become south for the remainder of the period.


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




NEAR TERM...Hastings
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