St. Johnsbury, Vermont 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

789
FXUS61 KBTV 090004
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
804 PM EDT Fri Aug 8 2025

.SYNOPSIS...
We are looking at an extended period of heat that is likely to
continue through at least the middle of next week. Many locations in
the Champlain and St. Lawrence Valleys will see at least 3 days of
90 degree temperatures with the possibility for 4 to 6 days of 90
degree temperatures. Elsewhere, temperatures will generally be in
the mid 80s to lower 90s through Wednesday. After today, we don`t
expect any rainfall across the region through the middle of next
week with high pressure overhead.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 126 PM EDT Friday...Afternoon showers and thunderstorms will
dissipate around sunset with clearing skies expected with the loss
of daytime convection. This will set up another good radiational
cooling night across the North Country with river valley fog
expected once again. For tonight, the most likely culprits for fog
will be along the Winooski and Connecticut River but we could see
some patchy fog anywhere where rainfall occurs; especially close to
sunset. Fog is expected to be less widespread tonight given lower
dewpoints (surface moisture) and a nocturnal jet of 10-15 knots
situated at around 1000 ft.

The warming trend will continue on Saturday with high temperatures
climbing into the mid 80s to near 90 degrees. Unlike the past
several days, we aren`t expecting and showers or thunderstorms as
increasing subsidence and warming temperatures aloft are both
expected to limit any diurnal instability. Model sounding suggest
very poor low and mid-level lapse rates may support some fair
weather cumulus but these clouds will likely have littler vertical
development due to the lack of buoyancy. Temperatures Saturday night
will be a few degrees warmer than tonight which will be a common
trend in the coming week as temperatures continue to steadily warm.
Fog is looking less likely Saturday night given an even stronger
nocturnal jet of 20 knots.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
As of 126 PM EDT Friday...Similar to Saturday, temperatures will be a
few degrees warmer than the previous day with high temperatures in
the upper 80s to lower 90s. Cloud cover will be minimal given very
limited moisture within the atmosphere and weak instability as
temperatures in the mid- levels continue to warm. Some locations will
see their second consecutive 90 degree day on Sunday which begins to
introduce increased risk for heat related illness. Luckily,
dewpoints will remain in the lower 90s and will limit heat indices.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 134 PM EDT Friday...A long duration period of much above
normal temps looks to continue most of next week with NWS heat
risk in the moderate to major level across most of our region.
The peak of the heat looks to occur on Monday and Tuesday with
values in the upper 80s to mid 90s with a few valley locations
in the upper 90s possible. Initially dewpoints look to hold in
the upper 50s to lower 60s, which wl keep apparent/feel like
temps similar to actual air temps. Still heat advisories maybe
needed for parts of the area.

As south/southwest winds strengthen on backside of sfc high
pres dwpts wl increase by mid week along with humidity values.
In addition, southerly winds and higher dwpts wl result in
warming overnight lows, especially for Monday night thru midweek
with lows only in the mid 60s to l/m 70s likely. Warmest values
in the SLV and CPV during this period. Still a large spread
with regards to magnitude and timing of a potential boundary
with slightly cooler wx for mid to late next week. For now have
chc pops on Weds/Thurs with cooler air arriving by late week.
This wl continue to be fined tuned as we become closer,
especially with regards to pops and impacts on temps. No
widespread rainfall is expected in the next 5 to 7 days, so our
stretch of very dry wx continues for most valley locations.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Through 00Z Sunday...Mostly a persistence TAF forecast followed
for the next 6 to 12 hours as areas of fog redevelop tonight
with mainly calm winds at the surface. Potential for IFR/LIFR
in fog/br overnight is roughly the same at MPV and SLK based on
the latest LAMP probs, in the the 30 to 40% probability range.
With recent light rain and BR present, have gone more aggressive
on fog development at SLK compared to guidance, especially
given what occurred last night. That being said, there is
definitely a bit more wind near the surface present and the
webcam at nearby Gabriels per NYS Mesonet shows less mist than
last night in the area. As such, think dense fog may be a bit
delayed compared to yesterday. Otherwise, have continued to show
IFR fog prevailing at MPV from 08Z to 13Z and tempo at EFK from
08Z to 11Z. Any fog will dissipate between 11Z and 13Z.
Generally light south winds through the remainder of the period.


Outlook...

Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
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. Slight chance SHRA, Slight chance TSRA.
Wednesday: VFR. Chance SHRA, Chance TSRA.

&&

.CLIMATE...
Record daily high temperatures are likely on Monday, August 11,
and Tuesday, August 12. Below are some of the records in
jeopardy of being broken:

Max Temp Records
Date     KBTV     KMPV      KMSS     KPBG
08-11            90|2016  93|2016  91|1970
08-12  93|2002   89|2021  91|1988  90|2007

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.

&&

$$
SYNOPSIS...Clay
NEAR TERM...Clay
SHORT TERM...Clay
LONG TERM...Taber
AVIATION...Kutikoff/Taber
CLIMATE...WFO BTV