792
FXUS61 KBTV 011031
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
631 AM EDT Tue Sep 1 2026

.WHAT HAS CHANGED...
As of 220 AM EDT Tuesday...

A Marginal Risk (level 1 out of 5) for severe thunderstorms has been
introduced to southwestern St. Lawrence County for Wednesday.

&&

.KEY MESSAGES...
As of 220 AM EDT Tuesday...

1. Rain along a stationary boundary will push through the
region this morning into early this afternoon, tapering off this
evening for most. Some isolated areas of drizzle will be possible
overnight mainly in eastern Vermont and the Adirondacks.

2. Heavier, more widespread, rain is expected Wednesday into
Wednesday night with some embedded thunderstorms. Isolated showers
will continue Thursday, mainly across Vermont.

3.  A few showers linger into late-week, trending drier through
the weekend.

&&

.DISCUSSION...
As of 220 AM EDT Tuesday...

KEY MESSAGE 1: Confluent flow driven by departing high pressure to the
southeast, and a stalled stationary boundary over the Great Lakes
and south into the Mid-Atlantic will push showers through the region
this morning into the early afternoon. Radar depicts a broad area of
light to moderate showers extending from the St. Lawrence Valley
into northeastern Ontario. This area of showers will ride along a
stationary boundary into northern New York with good isentropic
lift, before diving south into the Hudson Valley, following the
synoptic flow of the departing area of high pressure. Stratiform
rain is expected across much of northern New York and areas south of
I-89 in Vermont. The Northeast Kingdom may be able to stay dry
through much of the day today. Rainfall rates will be fairly light
with a thin warm cloud depth, in association with decently dry mid
levels. Rainfall may resemble light rain or drizzle intermittently
between showers. Most of the more persistent shower activity should
move south and east of the region by this afternoon, with just some
lingering light showers. Trends have kept the better instability and
thunder chances to our southwest in the quasi warm sector and along
the stationary boundary. Rainfall amounts through this evening are
expected to be less than half and inch with a quarter to a half an
inch southwest of a line from Massena, NY to the Orange/Caledonia
County border in Vermont. As showers depart this afternoon, low
level moisture will linger, though mid levels will remain fairly
dry. Thus, some drizzle may still linger into the overnight hours,
particularly in eastern Vermont where damed cold air will reside
under the approaching warm air from the west leading to further
isentropic lift. While it will not be a total washout today, with
likely breaks between showers, especially this afternoon, it will
likely be dreary. With the added cloud cover temperatures today
temperatures will struggle to get out of the 60s in our south and
western regions, with some warmer temperatures on the northern edge
of the shower activity near the International Border where mid 70s
will be possible.

KEY MESSAGE 2: A more dynamic system will push into the area Wednesday
into Wednesday night as the stationary boundary to our southwest,
drifts northeast closer to our region. A surface low over the Great
Lakes associated with a parent low in northeast Ontario will track
east from eastern Ontario. Showers are expected to move into the St.
Lawrence Valley by the early afternoon on Wednesday, though with
limited instability due to likely convective blowoff preceding
these showers. However by the mid to late afternoon models depict
good elevated instability above an inversion layer which could help
sustain some thunderstorm activity primarily in the later afternoon
and evening hours in the St. Lawrence Valley. 1000-1500J/kg of
MLCAPE associated with 30-40kts of 0-6km bulk shear would be ample
to support embedded thunderstorms towards the later afternoon. Any
stronger storms Wednesday afternoon, would be tied to northwestern
New York, and conditional on the amount of cloud cover and
antecedent convection. Temperature profiles likely will not be of
much help with surface temperatures in the mid to upper 70s
Wednesday afternoon. Should convection become self-sustaining in
Canada, it likely would be able to continue due to the available
MUCAPE to 1500-2000J/kg modeled across the St. Lawrence Valley. As a
result of this slight upward trend, the Storm Prediction Center has
added southwestern St. Lawrence County in a Marginal Risk (level 1
out of 5) for Severe thunderstorms Wednesday afternoon-Wednesday
night. As the showers and embedded thunderstorms continue to track
east Wednesday evening, a developing nocturnal inversion will help
decrease the threat of any stronger storms in addition to the
overall thunder chances. However, showers will still retain the
potential for heavier downpours into Vermont beyond sunset. Rainfall
rates in the HREF through Wednesday evening denote pockets of 0.25-
0.5"/hour rates across northern New York. A good wetting rain is
anticipated Wednesday night areawide with most areas expected to see
three-quarters of an inch to an inch of rain, with perhaps an inch
to 1.5 inches in the higher terrain of the Greens. Ensembles still
show a 20-50% chance of receiving an inch or more, with 2 inch
probabilities unchanged and less than 10%. While most of the area is
still in a Marginal Risk (level 1 out of 4) for the potential for
isolated Flash Flooding, the threat remains low and conditional upon
the heavy rain axis becoming colocated with the rain axis today.
Regardless, there will be several hours between rain events today
and Wednesdays in addition to marginal rainfall totals. The bulk of
the rain is expected to fall overnight Wednesday into Thursday
morning. The heaviest showers should depart early Thursday morning
to our east, though some lingering showers will still be possible in
eastern Vermont as a trailing cold front shifts east. Within this
thin warm sector a few pop up showers and isolated thunderstorms
will be possible Thursday afternoon, mainly in southern Vermont
where chances for any clearing will be highest. No severe storms are
expected at this time Thursday. Unsettled weather will finally trend
towards more quiet conditions as we near Friday and the weekend.

KEY MESSAGE 3: The upper-level low centered over central Quebec will
shift southeastward through Saturday.  Multiple shortwaves rotating
around the low will keep some scattered showers around, interspersed
with drier periods in between shortwaves.  Friday`s showers look
mainly focused over northwestern slopes of higher terrain with
northwesterly flow in place.  As the low further shifts away on
Saturday, flow will become northeasterly and thus favor showers on
the northeastern slopes.  Sunday will trend drier as the low moves
out to sea and high pressure builds in from the west.

Given the lingering upper-level low, temperatures will remain on the
cooler side of seasonal normals.  Highs through the weekend will
generally be in the 70s, with lows in the 40s and 50s.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Through 12Z Wednesday...Steady showers will continue over
southern portions of our forecast area through early this
afternoon. These showers will bring periods of reduced
visibilities in the 3-6SM range to KSLK and KRUT. Showers will
be more scattered at other TAF sites, but have included tempos
and PROB30s where appropriate for KMSS, KPBG, KBTV, and KMPV, as
they all remain along or just north of the line of steadier
showers. Thus, expect visibilities to bounce up and down at
these sites. Steady showers will come to an end early this
afternoon, though some additional lighter passing showers are
possible. Once the showers depart, low-level moisture will be
suppressed underneath a low-level inversion, setting the stage
for some low stratus and a trend towards low MVFR/IFR ceilings
after 06Z Wednesday.

Outlook...

Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA,
Slight chance TSRA.
Wednesday Night: Mainly MVFR, with local IFR possible. Definite
SHRA, Slight chance TSRA.
Thursday: Mainly MVFR, with areas IFR possible. Chance SHRA.
Thursday Night: Mainly VFR, with areas MVFR possible. Slight
chance SHRA.
Friday: MVFR. Chance SHRA.
Friday Night: Mainly VFR, with areas MVFR possible. Slight chance
SHRA.
Saturday: Mainly MVFR, with local IFR possible. Slight chance
SHRA.

&&

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

&&

$$

WHAT HAS CHANGED...Danzig
DISCUSSION...Danzig/Duell
AVIATION...Duell