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FXUS61 KBTV 201902
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
302 PM EDT Mon Jul 20 2026
.WHAT HAS CHANGED...
As of 302 PM EDT Monday...
Thunderstorm risk for Wednesday in Vermont has continued to
decrease.
&&
.KEY MESSAGES...
As of 302 PM EDT Monday...
1. Scattered showers and thunderstorms Tuesday afternoon and
evening, followed by a lower chance on Wednesday primarily in
northern and eastern Vermont. Strong wind gusts are possible with a
few storms, especially in southern St. Lawrence County.
2. Blue sky conditions for Thursday with cool and crisp air.
3. A warming trend at the end of the week followed by a chance
of thunderstorms Sunday.
&&
.DISCUSSION...
As of 302 PM EDT Monday...
KEY MESSAGE 1: Tranquil weather today will become dynamic on Tuesday as
an unseasonably strong low pressure system (roughly 992 millibars
over northeastern Ontario) drags multiple fronts through the area
through Wednesday night. Strong southerly flow between this low
pressure area and high pressure to our east will transport
increasing humidity following a couple of dry days, with dew points
climbing back into the 60s by afternoon. Generally with large scale
divergent flow ahead of a potent upper level trough, scattered
showers will develop Tuesday, while thunder risk is limited
by instability struggling to reach 500 J/kg. Greater
instability is favored in northern New York where a severe
thunderstorm risk remains.
Damaging wind gusts are driving the severe weather outlook for
tomorrow. The risk timing appears to begin roughly 2 to 3 PM, peak
around 4 to 6 PM, and diminish by 8 PM. Thunderstorms are
strongly favored downwind of Lake Ontario, then trend southward
into central New York and points south and east with time.
Therefore, in our forecast area the chances of these stronger
thunderstorms is much higher in St. Lawrence County and perhaps
Franklin County. These areas may have just enough favorable
ingredients for a localized wet microburst to occur; CAPE should
reach around 1000 J/kg, some mid-level dry air will be present,
and steep 0 to 3 kilometer lapse rates are favored given the
time of day and deep mixing promoted by the background wind.
Cell motions will tend to be from southwest to northeast given
the cloud layer flow, and there could be multiple rounds of
thunderstorms in this area. The latest HREF local probability
matched mean shows 6 hour precipitation approaching 3 inches,
and convection allowing models depict hourly rainfall rates
between 1 and 2 inches. Altogether, an isolated instance of
urban/flash flooding (affecting part of a town or two) is
possible along with the severe wind threat.
Farther east, peak instability is expected to diminish greatly,
in part due to some stable marine influence from south-
southeasterly flow and also due to potential daytime cloudiness
from scattered showers ongoing during the morning to our south.
As such, risk of thunderstorms of any variety is fairly low
from the Adirondacks eastward, especially towards northeastern
Vermont. Even in the most unstable air in our western areas, it
appears CAPE will be insufficient for supercells. So the
possibility of severe storms making it farther east is low,
contingent on cells organizing in a quasi-linear fashion and
sweeping eastward. That being said, a few rumbles of thunder
will be possible amongst widespread showers Tuesday evening
driven by cooling temperatures aloft, but the overlap of
sufficient moisture and instability is limited and would not
expect much activity overnight besides widespread showers.
Rainfall amounts will tend to average from 0.3" to 0.7", with
the typical locally higher amounts within thunderstorms
anticipated.
Based on the latest forecast data, the Wednesday convective threat
for Vermont has trended downward. Most guidance shows isolated
coverage of showers and maybe a thunderstorm or two developing
ahead of the lagging surface cold front during the midday or
late afternoon. If, and it`s a big if, there is enough
instability to overcome copious dry air aloft and associated
poor lapse rates in the mid-levels, ample deep layer ahead of
the front will support organized thunderstorms that would be
capable of strong winds, with probabilities increasing in
eastern Vermont. We`ll have to watch trends, but for now it
looks like a mainly quiet weather day with only slight chances
for thunderstorms.
KEY MESSAGE 2: An unseasonably cool air mass, with minimal high
altitude smoke, should make for outstanding weather for outdoor
activities on Thursday as an upper level trough pushes to our
northeast. Westerly flow in the morning will probably support some
rough conditions on Lake Champlain that should improve during the
day as anomalous low level temperatures moderate along with
decreasing wind speeds. Expect high temperatures not too far off of
seasonable norms due to abundant sunshine, currently projected to
range through the 70s.
KEY MESSAGE 3: A surface high pressure will dominate Friday and
Saturday, bringing a warming trend with it. Daytime temperatures in
valley locations will slowly rise from the upper 70s on Thursday to
the upper 80s by Sunday. We are tracking a low pressure system that
gets pushed north of our CWA by the upper level ridge. If the
current forecast holds this system will not impact our CWA. The most
impactful system in the extended will be an upper level trough and
associated surface front that comes through on Sunday. This system
is forecasted to bring a chance of rain showers and a slight chance
of thunderstorms Sunday into Monday.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Through 18Z Tuesday...VFR dominates throughout the day, with just
some fair weather Cu. Otherwise southerly winds with moderate
gusts throughout the day. Winds will die down overnight, with no
fog development anticipated. Tomorrow afternoon winds will pick
up along with a chance of showers and thunderstorms.
Outlook...
Tuesday Night: Mainly VFR, with local MVFR possible. Definite
SHRA, Chance TSRA.
Wednesday: Mainly VFR, with local MVFR possible. Chance SHRA,
Slight chance TSRA.
Wednesday Night: VFR. NO SIG WX.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. Slight chance SHRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
WHAT HAS CHANGED...Kutikoff
DISCUSSION...Langbauer/Kutikoff
AVIATION...Langbauer
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