Williston, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

826
FXUS61 KBTV 121804
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
Issued by National Weather Service Albany NY
204 PM EDT Tue Aug 12 2025

.SYNOPSIS...
Unseasonably hot conditions will linger into Wednesday as
humidity begins to increase ahead of a weak frontal system;
this will keep dangerous heat ongoing into the afternoon hours
for portions of the North County. As the front swings through,
isolated to scattered showers and  thunderstorms will occur,
with potential for a couple of stronger storms. Conditions turn
relatively cooler and drier for the end of the week before
warming again over the weekend. Early indicators point to
sharply cooler and drier weather early next week.

&&

.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
*A Heat Advisory remains in effect through Wednesday morning in
 the St. Lawrence and northern Champlain Valleys. Initially
 drier heat will become more humid through the day Wednesday,
 keeping conditions dangerous for those unprepared for hot
 temperatures.

High pressure and clear skies tonight give way to increasing
cloud cover, continued heat and rising humidity Wednesday. With
rising humidity, heat indices will become less neutral and begin
adding thermal stress as the day wears on, especially in
portions of the Champlain Valley. As such, the Heat Advisory was
extended through 8PM Wednesday here. Temperatures in the
mid/upper 90s today are still projected to only cool to around
70 degrees like last night, not allowing structures to
efficiently cool. Temperatures will not be as high Wednesday,
but rising dewpoints ahead of a broken frontal system will
promote heat index values greater than local temperatures. For
locations in the Champlain Valley where it will take longer for
showers to arrive, this will keep heat risk higher. Those
without adequate cooling should exercise caution and should
employ mitigation efforts such as limited time in uncooled
locations.

As dewpoints rise coincident to increasing instability and
forcing associated with the approaching broken frontal system,
shower chances will be increasing. CAMs and some global models
are projecting SFC based CAPE ranging from 1000-2000 J/kg. With
0-6 km shear still 20 kts or less, pulse variety cells are
anticipated. However, should outflow boundaries become deep
enough, cell induced shear could increase into the 20-30 kt
range, allowing for brief organization of cells. DCAPEs support
wind as a primary hazard outside of lightning since freezing
levels will be high, and a lack of shear will keep the hail
threat low. Bottom line, a few stronger storms will be possible.
By the evening, the surface front will begin sagging southward,
allowing for winds for northern tier counties to switch
northerly and begin cooling off.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
Relatively cooler conditions are projected with highs generally
in the upper 70s to mid 80s. The proximity of the boundary will
keep slight changes of showers ongoing for central and southern
locations. As the boundary drags out, temperatures will cool
further Thursday night into a more comfortable range in the 50s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
High pressure briefly builds down into the region from Canada
Friday, and it will bring in some cooler and less humid
conditions. However, the high will be relatively weak and its
residence time will be brief so it will only drop conditions
down to around climatological normals. Conditions will likely
remain warmer and more humid father south as the airmass will
have trouble making its way south due to brief and weak
advection. Return southerly flow will increase temperatures back
above climatological normals for the weekend and the humidity
will also increase. A cold front looks to pass trough from north
to south on Sunday, but while there is the potential for the
convection, the environment continues to look very marginal.
GEFS, EPS and CAN probs of more than 1000 J/kg pf CAPE are less
than 10% for the entire area, with the highest probabilities
further south, while the most favorable values of 0-6 km wind
shear look to be farther north and displaced from the best
CAPE. The front is expected to bring a more impressive change in
airmass, with temperatures looking to fall to around or below
climatological normals for parts of next week as large scale
ridging retreats to the southwest.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Through 18Z Wednesday...VFR conditions and mainly SKC will
prevail across all terminals through Wednesday morning.
Southerly winds will generally remain around 5-10 kts, though
will be higher in the valleys with around 10 kts at BTV, 10-15
at PBG and MSS along with gusts around 15-20 kts. Then after
00Z flow will still remain light enough for decoupling with
resumption of light/terrain driven flow.

A pre-frontal trough will move close enough to the area after
06Z to spread some clouds with bases around 5 to 10 kft into
northern New York and northwestern Vermont. These clouds will
be accompanied by widely scattered showers and storms,
especially near the MSS terminal towards the end of the period.
Confidence on exact timing of storms into the terminals is low,
and precludes mention in the current TAF.

Outlook...

Wednesday: VFR. Chance SHRA, Chance TSRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, Slight chance TSRA.
Thursday: Mainly VFR, with local IFR possible. Slight chance
SHRA, Slight chance TSRA.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.

&&

.CLIMATE...
Record daily high temperatures are were reached yesterday and
more will likely occur today:

Max Temp Records

August 11th - Observed|Record (Year)
KBTV         KMPV        KMSS        KPBG        KSLK
             91|90(2016) 95|93(2016) 91|91(1970) 90|93(1944)

August 12th - Forecast|Record (Year)
KBTV         KMPV        KMSS        KPBG        KSLK
95|93(2002)  91|89(2021) 94|91(1988) 92|90(2007) 90|93(1944)

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Heat Advisory until 8 PM EDT Wednesday for VTZ001-002-005-009-
     016-017.
NY...Heat Advisory until 8 AM EDT Wednesday for NYZ026-027-087.
     Heat Advisory until 8 PM EDT Wednesday for NYZ028-035.

&&

$$
SYNOPSIS...Boyd
NEAR TERM...Boyd
SHORT TERM...Boyd
LONG TERM...Myskowski
AVIATION...NWS ALY
CLIMATE...WFO BTV