Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 071722

Area Forecast Discussion
National Weather Service Burlington VT
1222 PM EST Thu Dec 7 2023

Colder than normal temperatures continue today with scattered
light snow showers across northern New York. A warming trend
begins Friday and continues through the weekend with
temperatures climbing well above normal, especially on Sunday. A
potentially strong storm system will move into the region
Sunday afternoon and evening, bringing rain and gusty winds
before ending as snow Sunday night into Monday. While some area
rivers could approach or exceed bankfull Sunday night into
Monday, significant flooding is not expected.


As of 1126 AM EST Thursday...Quick early afternoon update to the
forecast made to account for more areal coverage of prevailing
snow showers across southern St. Lawrence county, and to cool
max temps a bit based on current observational trends.
Otherwise, no changes made beyond today. Previous discussion

This morning, a shortwave trough slides southwest of our
region, bringing clouds and scattered snow showers to areas
mainly south and west of the Champlain valley where there is
better lift and moisture. With temperatures in the mid 20s to
low 30s, only a coating up to an inch of snow is expected. For
areas east of the Adirondacks and across Vermont, indications
are that after a cloudy start to the day, sunshine would return
by the late morning into the afternoon hours as the 925-700mb
level RH values fall to 30-50 percent range. However,
temperatures will remain unseasonably chilly in the 20s thanks
to a 1020mb surface high nosing in from Quebec and reinforcing a
pocket of -8 to -11C 925mb temperatures. For reference, typical
highs for early December across our region are in the mid to
upper 30s.

Heading into the overnight hours, the relative clear skies east of
the Greens as well as the albedo effect of the extensive snow cover
there will allow temperatures to plummet quickly into the single
digits, with a few negative readings across the Northeast Kingdom.
Cloud cover will be increasing across the Champlain Valley, so
expect mainly teens for overnight lows there and low to mid 20s
across the St Lawrence Valley. Snow showers could also linger across
the western zones into the southern Greens for a part of the
overnight hours, but expect a mainly quiet night of weather.

On Friday, a warming trend begins with temperatures moderating to
seasonal values. Upper ridging begins to build in with a 1024 mb
surface high sliding to our east during the day. It will be dry with
a mix of sun and clouds. High temperatures would generally be in the
30s across the region, with upper 30s to lower 40s possible for
portions of the Champlain and St Lawrence valley. Apparent
temperatures would be chillier with a southeast breeze but it should
feel relatively more comfortable to be outdoors compared to earlier
in the work week.


As of 350 AM EST Thursday...Quiet/dry weather this period as surface
high settles into the western Atlantic while upper ridging builds
into the region with winds trending steady south over time. This
will lead to significantly moderating temperatures with highs on
Saturday in the 40s to locally near 50 in the SLV with corresponding
lows Saturday night holding mild from 35 to 45.


As of 350 AM EST Thursday...The most impactful system of the 7-day
forecast to then affect the region Sunday into Monday.
Deterministic/ensemble solutions have begun to settle onto a
common theme, essentially painting a picture of a strong frontal
zone accompanied by a weak wave of low pressure riding
northward along the boundary through the region. These trends
now suggest any higher wind threat should be fairly limited.
However, copious moisture streaming northward along/ahead of the
front in combination with excellent dynamical forcing/upper
support should still produce steady moderate to occasionally
heavy rainfall across the region by Sunday afternoon/night. A
mix of blended QPF progs from favored output suggests a
widespread 1-2 inch event with scattered totals around 2 to 2.5
inches across southern counties, which will likely prompt
significant rises on area rivers due to snowmelt and runoff.
Ensemble hydrological output maintains higher probabilities of
several rivers at least nearing or exceeding bankfull by Sunday
night/early Monday so this will need to be monitored. However,
major flooding is not expected. Additionally, given the
relatively shorter duration of this warmup, the higher
elevations above 1500 feet will likely keep a good portion of
the existing early season snowpack, but significant settling is
certainly expected as rain will occur even at summit levels
Sunday afternoon/evening. As colder air streams in on the back
side of the boundary Sunday night, rain will likely change to
wet snow with early estimates and existing analogs suggesting a
few inches will be likely in the northern mountains with perhaps
a slushy inch or so in the broader northern valleys before
precipitation tapers off Monday morning. High temperatures to
run quite mild on Sunday (45 to 55) before values settle back
toward more seasonal values by later Monday/Monday night as
conditions trend dry.

Thereafter, a fairly quiet work week appears in store with
seasonably cool temperatures and mainly dry weather. A weak northern
stream clipper-type low may track through the region Wed/Wed night
with some scattered snow shower activity as suggested by GFS/ECMWF
deterministic output, but any accumulations should be minor. Daily
highs to generally run in the upper 20s to mid 30s with overnight
lows 15 to 25 or so.


Through 18Z Friday...VFR conditions at all sites this afternoon
will trend towards MVFR ceilings at KMSS/KSLK after 00Z and
after 04-06Z at all other sites except KEFK/KMPV. Brief IFR is
possible at KSLK as well from 08-14Z. Some light snow will
affect KMSS/KSLK this afternoon, but vsby should remain VFR,
maybe briefly MVFR at lowest. Winds will be light and variable
less than 5kts through the period.


Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: Mainly VFR, with local IFR possible. Chance SHRA.
Sunday: MVFR/IFR conditions possible. Definite RA.
Sunday Night: Mainly IFR, with areas MVFR possible. Windy with
gusts to 30 kt. Definite RA, Definite SN.
Monday: Mainly MVFR, with areas IFR possible. Likely RA, Likely
SN, Chance SHSN, Chance SHRA.
Monday Night: Mainly MVFR, with areas VFR possible. Slight chance
Tuesday: Mainly VFR, with local MVFR possible. NO SIG WX.




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