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Area forecast discussion
National Weather Service Burlington Vermont
940 PM EST Thu Nov 14 2019

Synopsis...
scattered snow showers across the region will generally wane tonight
ahead of a strong Arctic cold front which will move through the area
Friday afternoon and evening and could produce some strong
convective showers and snow squalls. An even colder air mass will
descend upon the region behind this front with record lows expected
again on Friday and Saturday night. This cold snap will be short-
lived with temperatures warming back to near normal values through
the beginning of next week.

&&

Near term /through Friday night/...
as of 940 PM EST Thursday...overall forecast in good shape.
Only minor tweak needed and that was to keep light snow going a
little longer in Vermont and limit it over northern New York
latest radar and surface observations. After midnight the
precipitation will come to an end across Vermont and lake band
off of Lake Ontario will get established over parts of northern
New York. Have tweaked forecast to account for this scenario
with rest of forecast unchanged.

Previous discussion...
no major changes to the forecast for the next 36 hours from
what we've been previously advertising. A warm front lifting
through the region today has been quite the overachiever with
many locations seeing off and more so on snow showers through
the day. Quantitative precipitation forecast has been rather light though given weak dynamics
other than the isentropic lift, with area webcams showing mainly
a dusting to perhaps a half inch in the heavier, more
persistent showers. As the front continues to lift north this
evening, scattered snow shower activity should generally wane
with the exception of up the St. Lawrence Valley where a
southwesterly fetch off Lake Ontario will aid in a continuation
of lake effect snow showers, mainly through pre-dawn with
accumulations generally an inch or less. Elsewhere, we should
also see low level moisture scour out across portions of the
forecast area, mainly east of the Adirondacks which will allow
temps to fall back into 20s despite increasing warm air
advection.

For Friday and Friday night the focus for the period continues to be
a strong Arctic front that will push into northern New York during
early afternoon and quickly traverse the forecast area from
northwest to southeast from late afternoon through the evening
hours. Driven by a strong jet streak of 100-125kts at 500mb and a
modest low level jet of 30-40kts at 925-850mb the front will be very
progressive with a residence time over any single location on order
of an hour to two at best, with a significant drop of 10-15 degrees
within 3-4 hours Post frontal passage as 925-850mb temps plunge back
into the teens below zero. Due to this strong temperature gradient,
a strong band of f-gen will likely develop along and ahead of the
front, and combine this with a couple hundred joules of Lake Ontario
enhanced cape and you've got the ingredients for not only convective
snow showers but also snow squalls. Based on the latest hi-res
guidance, the best forcing will occur between Malone and btv from
around 4-7pm and will likely disrupt the evening commute briefly
causing white out conditions with a quick accumulation of up to
couple inches of snow. As is typical with these fronts, as it tracks
eastward across the Adirondacks into the Champlain Valley the
mountains disrupt the forcing and lesser impacts are likely across
east/southeast Vermont with perhaps a dusting to an inch of
accumulation.

Ahead of the front temperatures Friday will warm back towards
seasonal values in the mid to upper 30s, but with high pressure
quickly building into the region Friday night, clearing skies, fresh
snow and cold temps aloft will support lows dropping back to near
record values in the single digits and teens above zero. A spot
below zero reading is certainly likely in the colder hollows of the
Adirondacks and Northeast Kingdom.

&&

Short term /Saturday through Saturday night/...
as of 327 PM EST Thursday...high pressure will be firmly in
control, and the airmass overhead will be very dry. Dewpoints
below -20 c extend from 975 to 700mb getting as low as -40 c off
forecast GFS soundings. There could be a few clouds to start
the morning with a narrow layer of moisture below the strong
inversion overhead, but by afternoon, you will be hard pressed
to find a cloud in the sky. With the polar air mass in place,
highs will only rise into the 20s. Overnight, expect single
digit temperatures across much of the area and falling below
zero across our cold hollows. A few record lows are under
threat. Interestingly, the NAM shows a thin layer of moisture
near the surface with light winds overnight. Most models are a
bit drier, but fog may not be out of the question.

&&

Long term /Sunday through Thursday/...
as of 327 PM EST Thursday...Sunday and much of Monday is
expected to be dry. As high pressure shifts offshore, we will
remain in a ridge axis extending southwest from the center.
Winds will begin to turn southerly, and we will moderate into
the 30s, and overnight lows will be in the teens to 20s.

Models are coming into better agreement regarding the next
system to come, though with differences in timing noted. A
negatively tilted upper trough will dig across the Great Lakes
right on the heels of a shortwave and coastal low moving east of
the 40 north/ 70 west benchmark. Confluent mid-level flow will funnel
moisture into the north country, and we will be placed in a
favorable left exit region of the jet. Light precipitation will
increase overnight Monday into Tuesday morning. Sounding
profiles suggest mixed precipitation, but anticipate this aspect
of the forecast to undergo changes, especially if the system
comes through during the day as opposed to overnight.

Several shortwaves will round the base of the upper trough
established over the Great Lakes before it gets kicked out next
Thursday. Temperatures remain below average through the period.

&&

Aviation /03z Friday through Tuesday/...
through 00z Saturday...as snow showers from earlier this
afternoon have largely come to an end, most taf sites have
improved to VFR flight conditions. VFR conditions with ceilings
in the 3000 ft to 6000 ft range will persist through the end of
the taf period for much of Vermont. Further west however, some
light lake effect snow showers over northern New York will
reduce ceilings and visibilities to MVFR ranges through the end
of the taf period. There will be some periods of brief
improvement as the lake effect band waffles back and forth, so
expect variable MVFR/low VFR conditions at kmss and kslk. A
line of snow squalls will move through northern New York after 20z.
These snow squalls will bring briefly heavy snow and gusty
winds, resulting in a quick period of LIFR/IFR visibilities. The
snow squalls will become less intense as they move into
northwestern Vermont after 23z.

Winds will generally be under 10 kts through 12z, however a
low-level jet overhead will result in some areas of low level wind shear
(especially across the Adirondacks and southern Vermont higher
terrain). After 12z, gusty southerly/southwesterly winds will
develop at the surface.

Outlook...

Friday night: VFR. Chance shsn.
Saturday: VFR. No sig weather.
Saturday night: VFR. No sig weather.
Sunday: VFR. No sig weather.
Sunday night: VFR. No sig weather.
Monday: mainly VFR, with areas MVFR possible. Chance ra, slight
chance freezing rain.
Monday night: mainly IFR, with local MVFR possible. Chance pl,
chance fzra, chance snow.
Tuesday: mainly IFR, with areas MVFR possible. Chance ra, chance
snow.

&&

Climate...
here are some min and low Max temperature records which could be broken over
the next few days.

Min temp records
datekbtv kmpv k1v4 kmss kpbg kslk
11-16 6|1967 4|1967 10|2003 0|1967 11|1967 -11|1933
11-17 7|1924 5|1972 20|2017 12|1980 14|1972 -10|1933

Low Max temp records
datekbtv kmpv k1v4 kmss kpbg kslk
11-16 22|1933 22|1967 31|2018 20|1967 29|1967 16|1933

&&

Btv watches/warnings/advisories...
Vermont...none.
New York...none.

&&

$$
Synopsis...lahiff

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