045
FXUS61 KBTV 261819
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
219 PM EDT Wed Aug 26 2026
.WHAT HAS CHANGED...
As of 219 PM EDT Wednesday...
Confidence in isolated severe thunderstorms has increased for
Thursday afternoon and evening.
&&
.KEY MESSAGES...
As of 219 PM EDT Wednesday...
1. Thunderstorms are increasingly likely Thursday afternoon and
evening, with greater chances in Vermont and particularly southern
areas. Some storms will be capable of strong winds and heavy rain.
2. Lingering and decreasing shower and thunderstorm threat for
Friday followed by beautiful weather to start the weekend.
3. Unsettled weather with increasing chances for precipitation
expected for early next week.
&&
.DISCUSSION...
As of 219 PM EDT Wednesday...
KEY MESSAGE 1:
Likelihood of numerous showers and thunderstorms for Thursday
afternoon and evening continues to increase today in portions of
northern New York and Vermont. Big picture: isolated severe
thunderstorms areawide remain possible east of the St. Lawrence
Valley. If confidence in location and intensity of thunderstorms
increases tonight, this outlook could very well change. Strong
moisture advection will occur ahead of a cold front with well
aligned southwesterly flow and mainly southerly winds at the
surface. Plenty of solar heating to start the day concurrent with
the incoming trough cooling temperatures aloft will aid in
blossoming instability. MLCAPE will surge into the 1000-1500 J/kg
range across the Champlain Valley and central Vermont during the
afternoon as surface temperatures and dew points will likely be in
excess of 80 and 60. About 30-35 knots of deep layer shear and
similar effective shear will likely be present. Overall, the
CAPE/shear balance appears to be sufficient for some stronger
variety thunderstorms and possible low-topped supercells to form.
In our region, the most likely timing for thunderstorms, including
isolated severe storms, appears to be from about 4 to 8 PM. The
greatest risk area is somewhat uncertain, but favors the region from
the eastern Adirondacks into at least the western half of Vermont.
Storm initiation may be upstream in central or eastern New York
earlier in the afternoon where the best instability will be located,
with cells moving parallel to the flow towards the northeast into
our region coincident with a warm front. This boundary will help
winds turn to more of a southeasterly flow near the surface across
the southern Champlain Valley into portions of central Vermont; with
some low level convergent flow along with terrain-generated lift,
storms may tend to strengthen during the evening as 0-1 km storm
relative helicity increases. The low level spin/veering winds will
aid in organized, stronger storms that could be more long lived than
a typical thunderstorm. All hazards with these storms are on the
table, with the most likely one being straight line winds. The
greater the instability, the more likely these hazards come to
fruition. At this time, a greater risk/more coverage of stronger
storms is favored south of our region per consensus of both the
physically-based and machine learning model guidance.
There is also a localized flash flood threat with this event,
particularly in the evening and in south central/western portions of
Vermont. While precipitable water will not be particularly high,
values in excess of 1.5" and/or 85th percentile for the time of year
will be sufficient for heavy rain. Additionally, integrated vapor
transport from the southwest coincident with deep moisture will be
present. Some CAMs show a plausible, but unlikely, scenario in which
multi-cell thunderstorms that had been propagating southeastward
stall out for a couple of hours, repeatedly moving over the same
areas and producing locally 2+ inches of rainfall within three
hours. Some slight pressure rises and pause in height falls are
noted during this period, which can contribute to stalling of
convection that was previously moving along. There remains mixed
signals among CAMs during the latest model cycle on this potential,
so confidence is fairly low on flash flooding, but note training
thunderstorms are possible if ingredients line up.
KEY MESSAGE 2: Deep moisture will be shunted to our east by Friday
morning. As such, the only limited thunderstorm potential will be
tied to the lingering surface cold front which will most likely be
passing uneventfully through the region during the morning. It
appears it will get hung up just enough over southern Vermont that a
small window during the afternoon hours where showers develop along
the boundary exists such that a thunderstorm is possible in south
central to southeastern portions of the state, especially if these
areas break out into some sunshine. Abundant dry air aloft points to
widely scattered showers, so only a very select few locations will
see hazardous weather as showers will struggle to produce lightning.
Thunderstorm probabilities have fallen into the 10 to 13% range in
southern/eastern portions of Vermont (contrasted with 30-40% in much
of the area on Thursday). Following any convective activity during
the afternoon, a very pleasant air mass will continue advecting in
from the northwest Friday night setting the stage for a gorgeous,
sunny day with low humidity for Saturday as ridging builds in at the
surface and aloft. High temperatures should be very seasonable,
ranging through the 70s.
KEY MESSAGE 3: High pressure will slide to our east on Sunday, and at
this point, expect the second half of the weekend to be mainly dry.
Uncertainty grows thereafter as an upper trough swings across Quebec
and into northern/eastern New England, sweeping a cold front along
its wake. There remains considerable spread in model solutions with
this system, particularly how far southward the front makes it
before possibly lifting back north as a warm front as low pressure
slides to our north. For example, the 12z GFS solution sets up the
front directly over our region, with waves of low pressure to slide
along it from later Sunday into mid week. The result is a period of
particularly wet and cooler weather. Do note the GEFS ensembles
don`t support the operational solution, with 24-hr probabilities of
greater than a half inch of rainfall remaining fairly low.
Meanwhile, the 00z ECMWF isn`t so dire, lifting the cold front back
to our north Monday into Tuesday, keeping rounds of showers more
transient and allowing us to warm back up into the 80s by mid week.
Have not made changes to the NBM from Sunday onward given the
uncertainty, but it`ll be interesting to see how trends play out as
we draw closer to next week.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Through 18Z Thursday...VFR conditions will prevail for much of the
TAF period with fair weather cumulus remaining SCT AOA 3500 ft
through this evening. Clouds dissipate toward sunset, with a few
mid/high clouds expected overnight. Patchy fog will be possible late
tonight/early Thursday morning, mainly along the favored river
valleys in eastern VT. Periods of IFR/LIFR conditions are expected
due to fog at MPV 08z-12z Thu, with less confidence of
significant impacts at EFK. Clouds increase again after 12z Thu
ahead of an approaching frontal boundary, but VFR should prevail
with shower/thunderstorm development holding off until late in
and/or after this forecast period. Winds generally 5 kt or less
this afternoon and overnight. Only exception will be a SE lake
breeze at PBG, where sustained winds will remain closer to 10 kt
until 23z. Winds will begin to increase later tonight and
especially during the daylight hours on Thu. Expect S/SW winds
around 10 kt with gusts of 16-20 kt.
Outlook...
Thursday Night: VFR. Chance SHRA, Slight chance TSRA.
Friday: Mainly VFR, with local MVFR possible. Chance SHRA, Slight
chance TSRA.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: Mainly VFR, with areas MVFR possible. Chance SHRA.
Monday: Mainly MVFR, with local IFR possible. Chance SHRA, Slight
chance TSRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
WHAT HAS CHANGED...Kutikoff
DISCUSSION...Kutikoff/Hastings
AVIATION...Hastings
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