Area Forecast Discussion
Issued by NWS Burlington, VT

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FXUS61 KBTV 072025

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

After another cold night tonight, a warming trend begins Friday and
continues through the weekend with temperatures climbing well above
normal, especially on Sunday. A 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 325 PM EST Thursday...Mainly quiet conditions are expected
through the period with lingering snow showers across the North
Country this afternoon ending this evening. Weak shortwave energy
associated with an exiting trough and on the leading edge of an
upper ridge just west of the Great Lakes produced some light snow
showers across the North Country this afternoon, surprisingly
reducing visibility to below 2 miles in some spots. Not seeing any
real accumulations on area webcams, so the impact was basically nil.
As we move into the evening hours, the upper level support and mid-
level moisture wanes across the region and thus, we should see snow
showers reduce in areal coverage. Cloud cover will be tricky
overnight as 1000-850mb moisture increases from west to east, and
this is easily seen on afternoon GOES-R satellite imagery. To the
east though, moisture is thinning east of the Greens so a period of
clearing skies is expected which will help to produce colder min
temps tonight. Basically looking at lows in the teens to low 20s
from the Champlain Valley westward as well as southern Vermont, with
central/northeast Vermont ranging from 5 below to 10 above.

As the aforementioned upper level ridge slowly edges eastward over
the Great Lakes on Friday, and the Northeast Friday night, dry
conditions continue along with a notable warming trend. Temps during
the day will warm back to normal values for early December to
slightly above normal with highs around freezing along the
international border to upper 30s and around 40 south. Temps cool a
bit overnight, but with increasing SSW flow they`ll hold in the 20s
east to low 30s west.


As of 325 PM EST Thursday...A relatively quiet period of wx
anticipated as 925mb to 500mb southwest flow develops with moderate
waa. Weak embedded s/w energy in the flow aloft, combined with some
modest 925mb to 850mb lift may produce spotty light precip on Sat
aftn into Sat night. Depending upon near sfc temps, pockets of
freezing drizzle could be possible acrs northern NY Sat night. Attm
confidence of precip and bl temps is marginal so have not included
in the fcst. Progged 925mb temps btwn 6-8C support highs near 40F
NEK to near 50F southern SLV, with a wide range in lows on Sat
night, as deeper valleys east of the Greens decouple. Expecting lows
mid 20s NEK/eastern VT to l/m 40s SLV/CPV.


As of 325 PM EST Thursday...An active period of wx still is
anticipated on Sunday into Monday with several potential hazards.
System continues to evolve with several changes/trends noted in the
12z guidance as energy/trof of interest is entering the Pacific NW
attm. Water vapor shows a rather complex trof with numerous embedded
s/w, along with abundant deep layer moisture advection. This system
wl travel acrs the inter- mountain west thru Friday, before multiple
pieces of s/w energy eject into the central/high Plains. Initial s/w
energy wl help develop weak low pres over the western Great Lakes
with cold frnt extending into the MS River Valley. Meanwhile,
additional s/w energy crntly over the PAC NW wl dig on backside,
helping enhance a deep full latitude mid/upper lvl trof acrs the MS
Valley/central Appalachian Mtns by Sunday. Several waves of sfc low
pres develop along the cold frnt, as its progresses eastward into
the Mid Atlantic/NE CONUS on Sunday night into Monday. Deep
southerly flow associated with full latitude trof ahead of sfc
boundary/low pres wl advect pw values over 1.0" into our cwa, which
is 3 to 5 STD above normal for early/mid Dec. This moisture,
combined with developing dual 25h jet structure, a slight negative
tilt to the trof axis and enhanced ribbon of 850 to 700mb fgen
forcing, supports a 6 to 12 hour window of moderate to heavy
rainfall late Sunday into Monday from west to east acrs our cwa.
Based on above ingredients, thinking qpf ranges from 1 to 2 inches
with localized amounts up to 3 inches possible, especially parts of
the central/southern Greens. Thinking about 2 inches is likely here
in the CPV, especially given the deep southerly flow paralleling the
boundary, with deep moisture advection. Instability is minimal, so
hrly rainfall rates should minimize potential for flash flooding,
but potential needs to be watched closely, especially when combined
with snowmelt. These anticipated qpf amounts and snowmelt wl cause
sharp rises on many streams and rivers, with several rivers having
the potential to reach minor flood, including the Otter Creek,
Ausable, Mad, and Missisquoi. If crnt trends continue a flood watch
maybe needed for portions of the region in later fcsts.

Next question is how quickly cold air develops on backside and rain
changes to snow from west to east acrs our cwa. The latest
experimental Winter Storm Outlook product from WPC has dropped the
northern Dacks into the 30 to 50% range of exceeding warning
criteria, along with parts of the northern Greens. Its always
extremely challenging to capture the exact thermal profiles, given a
sharpening thermal gradient and timing of rain changing to snow in
these scenarios. In addition, how much moisture lingering behind the
boundary wl play an important role in the amount of accumulating
snowfall on backside. If system stays positively tilted and more
progressive as supported by some guidance, snowfall wl be limited,
but if trof becomes negatively tilted and slower, heavier snowfall
for the mtns is possible. Our crnt thoughts suggest the best
potential for accumulating snowfall of at least 3 inches or more
would be acrs the northern Dacks into portions of the
central/northern Greens above 1000 feet. Depending upon the timing
of rain changing to snow, a slippery Monday morning commute is
possible acrs portions of our cwa. For now we have the general idea
of rain changing to snow acrs the dacks, followed by
northern/central Greens and eventually into the CPV by Monday
morning. Thermal profiles support highs mid 40s to l/m 50s Sunday,
with values holding steady overnight until falling sharply as the
boundary crosses our region toward Monday morning. Highs Monday
range from the mid 20s dacks to mid 40s lower CT River Valley.

Another trend is for less wind given weaker area of low pres, very
stable low levels associated with precip, and strongest 925mb to
850mb wind fields displaced slightly to our south and east.
Strongest 850mb winds of 45 to 50 knots occur on Sunday morning acrs
the dacks, where summit gusts up to 50 mph are possible, but much
weaker in deeper valleys, with gusts ranging in the 20 to 30 mph

For midweek, much quieter wx anticipated with temps returning to
near normal and chances of mostly mtn snow showers. GFS is
advertising a cold frnt on Weds with some slightly better
moisture/forcing which could produce a period of light accumulating
snowfall. Did lower highs a bit for midweek, especially associated
with 850mb temps near -15C and 925mb values ranging btwn -8 and -
12C, supporting mostly 20s to lower 30s.


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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