465
FXUS61 KBTV 030620
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
220 AM EDT Wed Sep 3 2025

.SYNOPSIS...
The warmer weather will continue today but the humidity will remain
low. A few scattered showers will be possible in the afternoon, but
more widespread rain will arrive Thursday afternoon into Friday
ahead of a large upper low. In addition to wetting rain, there will
be some stronger winds Thursday and Friday, especially in the
Champlain Valley and far northern Adirondacks.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 219 AM EDT Wednesday...With mostly clear skies, calm winds and
a dry airmass, radiational cooling has been efficient during the
night. Despite above average temperatures during the day, the are
falling back to around normals. Patchy fog has begun to develop in
the favored valleys and in places that saw rain yesterday, and it
will continue to expand in coverage for the rest of the night.
Surface high pressure will gradually push off to the east today, and
southerly flow will begin to develop. Temperatures should rise a
degree or two higher than today but the humidity will stay low. A
southerly low level jet moves overhead tonight, increasing winds in
the Champlain Valley and northern Adirondacks. It should also
restrict fog to the most protected valleys of eastern Vermont and
keep temperatures milder than the past few nights.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY/...
As of 219 AM EDT Wednesday...A deep trough will gradually move into
the region Thursday and Friday, bringing a couple fronts. The first
enters northern New York tomorrow afternoon and reaches Vermont in
the evening. It should bring a wide line of rain along with it. Some
embedded convective elements are possible, but with very weak
instability, there is a low severe threat. However, with a strong
low-level jet overhead, it will not take much to mix some of the
stronger winds to the surface so some gusty showers are likely. The
highest chances for thunder are over northern New York where the
instability and synoptic forcing will be greater. The front`s
evening and nocturnal passage in Vermont and weakening synoptic
forcing should keep the precipitation mostly plain rain there. While
a few showers are possible on Friday, it looks to be in a gap
between fronts so it should be mostly dry, before another weaker
front approaches for the evening. A southerly low level jet will be
overhead during the day Thursday, bringing gusty winds. It will
channel up the Champlain Valley and downslope across the far
northern Adirondacks, where gusts above 30 mph are possible.
Elsewhere, they should be in the 15- 25 mph range. Dry weather for
much of Thursday and some sunshine should allow for decent mixing,
despite an initial warm-air advection profile. Relative humidities
will also drop into the 30-40 mph range for most places, and
combined with the gusty winds, there are fire weather concerns
before the rain arrives.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 219 AM EDT Wednesday...* Beneficial, widespread rain is likely
Saturday * There is a low (~10-15%) chance of heavy rainfall of at
least 1"  on Saturday in northern/eastern Vermont, especially if
thunderstorms develop * Mainly dry & cool early next week

Friday night looks warm and breezy as the old front washes out over
the area and a new wave helps to blossom showers to our south or
southwest towards Saturday morning. Per NAEFS mean integrated water
vapor transport (IVT), anomalous southwesterly IVT will be present
along the boundary, and a seasonably strong upper jet (250 millibar
winds > 110 knots) will be situated to our north. These features
support widespread showers with some heavy rainfall rates, which
could be slow to move eastwards given deep southwesterly flow from
the surface to high altitude out ahead of the front.

There seems to be good agreement amongst most ensemble guidance that
the bands of showers with embedded thunderstorms will be positioned
over either far northeastern New York or western Vermont and points
east by midday Saturday before pushing gradually eastward through
the remainder of Vermont during the rest of the day. Faster timing
in some guidance may be why the six-hourly PoPs are a little lower
than what would be expected given higher likelihood of rain - would
think in eastern parts of our region rainfall is nearly certain with
this system, consistent with 90- 100% chance of measurable rain from
Friday night through Saturday night in the region (except 65-90% in
the St. Lawrence Valley). There is a lot of spread in potential
rainfall amounts, but areas east of the Green Mountains do have the
greater potential for a good soaking rainfall with this event. We`ll
have to watch if the wave is too progressive such that the heavy
rain mostly passes through New Hampshire and points north and east.

No significant weather is anticipated Sunday through Tuesday, with
temperatures generally in the upper 30s to near 50 at night and in
the 60s to low 70s during the day.

On Sunday behind the frontal wave, relatively gentle cool air
advection should take place with lack of northwest flow. Instead,
925 millibar west-southwesterly flow could lead to some lake-effect
rain showers from Lake Ontario into southern portions of northern
Adirondacks and possibly central Vermont. Predictability right now
is too low to indicate with much detail. While both Monday and
Tuesday will probably be dry, there is some spread in the global
ensembles to make it difficult to be specific other than there
doesn`t seem to be much air mass change coming as temperatures
remain a bit below normal. While the long wave trough axis will
likely make it to our east by Monday, there is a multi-model
ensemble scenario that disagrees with this idea which could linger
cloudier conditions and shower chances. And then relatedly on
Tuesday, while some upper level ridging will likely build into the
region with more sun and a bit warmer weather, the next trough could
be quickly on its heels such that clouds and rain chances could come
ahead

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
It remains a fog forecast for our airspace; besides fog, VFR
conditions are ahead under high pressure. Currently 1/4 to 3/4 SM
visibility is being observed at SLK and EFK where rain fell prior to
sunset. We can expect perhaps brief fluctuations but largely LIFR
conditions to continue through daybreak at these sites. Historically
on these types of nights, SLK remains LIFR through 11Z and then
improves around 12Z, with a slightly later timeframe at EFK.
Meanwhile, while fog has yet to form at MPV, think it`s on track to
see dense radiation fog form as it did two nights ago, but with a
later start and possibly earlier cessation time. Climatologically
with lack of fog at 06Z, there is about a 50% chance of IFR
conditions, peaking in between 10Z and 12Z, or closer to 20% chance
per LAMP guidance, but think timing is more the challenge than its
eventual development given clear skies and light winds at this site.

Otherwise, there will be a little bit of channeled southerly flow
around 12Z to 15Z for enhanced winds at BTV with a period of 15 knot
gusts indicated, while winds generally will be light southerly today
across the airspace. Have also brought in VCSH at SLK and EFK after
18Z, with potential repeat of diurnally driven showers nearby with a
low chance of a direct hit.

Outlook...

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

&&

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

&&

$$
SYNOPSIS...Myskowski
NEAR TERM...Myskowski
SHORT TERM...Myskowski
LONG TERM...Kutikoff
AVIATION...Kutikoff