Williston, Vermont Weather Forecast Discussion

374
FXUS61 KBTV 052338
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
738 PM EDT Fri Sep 5 2025
.SYNOPSIS...
A cool and unsettled weather pattern is expected this upcoming
weekend with several rounds of showers anticipated, especially on
Saturday. Additional terrain and lake effect showers are possible on
Sunday across northern New York into parts of central and northern
Vermont. Temperatures will hold mainly in the 60s, except mid 70s on
Saturday in the Connecticut River Valley, with mostly 60s to near 70
on Sunday. Cool and dry weather is expected for the start of next
week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 155 PM EDT Friday...GOES 19 water vapor shows deep mid/upper
lvl trof acrs the Great Lakes with a vertically stacked low pres
system near Hudson Bay. A well defined mid lvl dry slot has resulted
in mostly sunny skies today, but a narrow axis of moisture and
associated 700-500mb vorticity channel is approaching the eastern
Great Lakes attm. This energy and moisture, along with weak
secondary trof wl swing from west to east acrs our cwa btwn 00z-08z
tonight, with broken line of showers. Have included 30 to 40% to
cover this potential overnight, but given lack of deep layer
moisture, feel areal coverage wl be limited. Soundings suggest good
bl mixing with tightening gradient associated with sfc trof, so not
anticipating much fog development overnight with temps holding in
the mid 50s to mid 60s. Warmest in the CPV where southerly winds are
expected to be the strongest.
Our next system for Saturday is a combination of northern stream
energy over the northern Plains and deeper moisture and stronger
dynamics over Iowa, that wl phase together and ride along tightening
thermal boundary to produce widespread rain showers. Noted both
NAM/HRRR show weak sliver of instability developing over southeast
sections, to support an embedded rumble with slightly better
rainfall rates. Most of northern NY and central/northern VT wl be
post frontal with cool strato formed precip anticipated, with temps
holding in the mid 50s mtns to mid 60s valleys, except mid 70s near
VSF. Have coordinated with WPC to remove our entire fa from day 2
ERO, as most of our cwa remains in moderate/severe drought, plus
without instability hourly rainfall rates wl remain below 1/3 hr
ffg, which is 2.0 to 4.5 inches. Total qpf looks to be in the 0.25
to 0.75 with a few localized higher amounts in convective elements
over southern sections near 1.0 possible on Sat.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 155 PM EDT Friday...Mid/upper lvl trof prevails acrs the
central Great Lakes with strong southwest flow aloft. A potent s/w
is progged to be approaching the SLV around 12z Sunday, combined
with lake enhanced moisture from favorable southwest flow and weak
layer of instability per sounding data, have increased pops over
northern NY into the mtns of central/northern VT on Sunday. In
addition, weak sfc convergence wl help to enhance precip chances,
especially northern dacks and parts of central/northern Vt mtns.
Moisture is limited, so areal coverage should be mostly confined to
the trrn with qpf of a tenth or two at most. Temps are tricky on
Sunday with southwesterly flow here in the CPV, with a few breaks,
feel highs could warm into the lower 70s, while upper 50s to mid 60s
prevail in the trrn with cloudy skies. A few breaks are possible in
the morning, before dynamics arrive. 1026mb sfc ridge builds into
our region Sunday night into Monday, with clearing skies and cooling
temps. Areas of fog/mist are likely toward 12z Monday, as temps cool
back into the mid 30s SLK/NEK to lower 50s near Lake Champlain.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 130 PM EDT Friday...On Monday we will continue to be
under the influence of an upper level trough though a ridge of
surface high pressure will build also. This will lead to a cool
and cloudy day Monday and can`t rule out a light rain shower as
well. Surface high will begin to slide eastward overnight, but
conditions should still be calm enough for some fog formation
early Tuesday morning. Upper level ridge builds over the area on
Tuesday and flow becomes more southwesterly, leading to some
warmer temperatures for Tuesday and Wednesday. During Wednesday
night and Thursday an upper level trough will cross the region,
along with a very weak surface front. Do not think we`ll see
much more than clouds on Thu, but a slight chance of showers is
included. Temperatures will also be pretty cool Thursday but
will be short lived as southerly return flow develops again on
Friday.
&&
.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Through 00z Sunday...Conditions are currently VFR with south to
southwest winds around 5 to 10 knots. Clouds around 7000-10000
ft agl will continue to pass through the region. Over the next
few hours, winds at 2000 ft agl will increase out of the
southwest to 35 to 45 knots. This is expected to result in
pockets of LLWS, especially across Vermont, from about 01z to
07z. This surge of wind will also bring hit or miss showers.
PROB30s are noted for a few hours overnight at all terminals.
Though decreasing, winds off the surface will remain elevated
while high clouds begin streaming out of the southwest, and this
will likely prevent fog. If anyplace could get fog, probabilistic
data suggests KMPV is the most likely. Given uncertainties,
have opted for 3SM for now from 07z to 13z. Beyond 13z, a wave
of showers and embedded thunderstorms will lift northeast across
the region and begin to exit east of Vermont about 22z-23z.
Ceilings and visibilities could drop to MVFR in association with
rain, and heavier convection could produce localized IFR
conditions.
Outlook...
Saturday Night: VFR. Chance SHRA.
Sunday: VFR. Slight chance SHRA.
Sunday Night: VFR. NO SIG WX.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. NO SIG WX.
&&
.MARINE...
A Lake Wind Advisory continues for increasing south winds 15 to
25 knots this afternoon into the overnight hours. As of 7:30
PM, there has been little observed sustained or gusty winds up
to Lake Wind Advisory criteria. However, a wide range of model
data supports the development of a nocturnal southerly jet
channeling through the Champlain Valley. Winds are still
expected to increase, especially as we lose daytime heating,
mixing should become a bit more favorable. Waves will build 1 to
3 feet with some higher swells possible in the open waters.
Winds and waves decrease after midnight tonight.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Taber
NEAR TERM...Taber
SHORT TERM...Taber
LONG TERM...Neiles
AVIATION...Haynes/Neiles
MARINE...BTV

NWS BTV Office Area Forecast Discussion