711
FXUS61 KBTV 021819
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
219 PM EDT Sun Aug 2 2026
.WHAT HAS CHANGED...
As of 217 PM EDT Sunday...
Winds may be breezy to locally gusty, especially on mountain summits
tomorrow afternoon. A strong thunderstorm is also possible, mainly
in eastern Vermont late tomorrow morning into early tomorrow
afternoon. Otherwise no significant changes to the current forecast.
&&
.KEY MESSAGES...
As of 217 PM EDT Sunday...
1. Showers and embedded thunderstorms will increase across the
region today and tonight. Locally heavy rainfall possible,
especially in the St. Lawrence Valley.
2. A strong thunderstorm is possible late tomorrow morning into
the early afternoon, with breezy conditions along a cold front,
before conditions trend calmer and drier into mid week.
3. Seasonably warm and unsettled weather expected for the
latter half of this into next weekend.
&&
.DISCUSSION...
As of 217 PM EDT Sunday...
KEY MESSAGE 1: A slow moving upper level trough with associated closed
surface low is beginning to enter the St. Lawrence Valley with the
axis currently over eastern Ontario. Open wave showers and embedded
thunderstorms within an area of 1000J/kg MUCAPE are tracking
parallel to the St. Lawrence River, mainly west of the US-11
corridor. This baroclinic zone will serve as the focal point for
multiple rounds of showers throughout the day in the St. Lawrence
Valley. Recent model guidance has continued the trend of keeping the
heaviest of the convection and rain just across the International
Border into Ontario. Nonetheless, given PWs to 1.8-2", and deep warm
layer cloud depths, heavy rain is still possible in western St.
Lawrence County where 1 to 1.5 inches of rain are expected through
tonight. Locally up to 2 inches will be possible, especially under
any convective elements in western St. Lawrence County. The WPC
continues to highlight the St. Lawrence Valley with a Slight Risk
(level 2 out of 4) for a 15% chance of exceeding flash flood
guidance. While isolated urban flash flooding cannot be ruled out,
significant enough rainfall capable of producing flooding is not
anticipated over the prevailing flatter terrain. Outside of the
North Country showers, channeled flow in the Champlain Valley will
lead to intermittent gusts up to 25 mph near Lake Champlain. These
gusts will taper down with the arrival of showers this evening.
The deformation boundary, and associated showers, will shift east
into the Champlain Valley and Vermont this evening into tonight. A
few spot light showers may be possible across Vermont this
afternoon, but most will remain dry until later this evening. There
is good agreement that overnight Sunday should have the better
rainfall coverage and contain the bulk of the rainfall. A few areas
of brief 0.25-0.5 inch/hour rates will be possible across northern
New York within the boundary as it shifts east towards Vermont.
Rainfall across Vermont is expected to range between half an inch
and and an inch, with the higher amounts across the central and
northern Greens.
KEY MESSAGE 2: A clearing cold front will sweep across the entire
region from west to east, early to mid tomorrow morning, reaching
Vermont by late tomorrow morning. Wrap around moisture along the
convergent deformation band in northern New York will likely lead to
some continued light shower chances (only 30-40%) through tomorrow
afternoon. In Vermont, modest instability and shear could lead to an
isolated strong thunderstorms in the late morning to early afternoon
hours, primary east of VT-100. SBCAPE increases to 500-1500J/kg,
with 30-40kts of shear would be sufficient for potentially an
isolated strong thunderstorm. However, lingering low clouds from
overnight rains, and competing updrafts along the front, may lead to
lesser chances. The SPC does place most of eastern Vermont in a
Marginal Risk (level 1 out of 5) for an isolated severe thunderstorm
tomorrow afternoon. Expectations are that most storms if they
develop would be sub-severe with plenty of cloud cover and
stratiform rain around, but an isolated strong thunderstorm cannot
be ruled out if an area can break out of the clouds and tap into
some diurnal heating. Associated with the cold front, breezy, to
locally gusty, winds are expected along the higher terrain and
Champlain Valley tomorrow. As the front swings east, and associated
strengthening 40-50 knot low level jet will move along the northern
portions of the region. Gusts on summit levels could gust up to 30-
35 MPH, with valley winds around 20-30 MPH, mainly between 2 and 8
PM. Winds will temper down with sunset and the development of a
nocturnal inversion.
Showers and thunderstorms will taper off for most by late Monday
afternoon. Lingering northwest wrap around flow could lead to some
continued stubborn shower chances along the higher terrain of the
northern Greens and Adirondacks Monday night. Across eastern
Vermont, fog development appears likely in the valleys of the region
with brief high pressure nudging in from the west, and calming
winds. Tuesday and Wednesday will be quieter and calmer with
temperatures in the upper 70s to mid 80s and mostly clear skies.
Dewpoints will slowly creep up by mid week however, approaching the
mid 60s in some places.
KEY MESSAGE 3: No significant changes to the forecast for later this
week/next weekend, as we look to remain squeezed between a strong
Bermuda high to our east and troughiness across the Northern/Central
Plains. This will place us square under broad W/SW flow, with upper
shortwaves occasionally rippling overhead. Humidity will increase as
moisture streams northward into our region; dewpoints look to
approach 70F with PWATs of 2+ inches Thursday and Friday. Models
differ on how long this persists, with a potential frontal passage
sometime over the weekend, but this is highly uncertain at this
time. In the meantime, we can expect rounds of showers and a few
thunderstorms through the end of the week. With no real strong
forcing and relatively warm air aloft limiting available CAPE, don`t
anticipate any severe weather at this time. Locally heavy rain will
be possible, but flow should be enough to keep showers/storms
moving, limiting any flood threat.
&&
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Through 18Z Monday...VFR conditions to mainly prevail through 00z Mon
with isolated to scattered showers to occasionally lower visibility
and/or ceilings to MVFR. The bulk of the activity through this
afternoon and evening will be over northern NY, particularly KMSS,
where a few thunderstorms will also be possible. Showers become more
widespread from 00z Mon onward, spreading from west to east ahead of
an incoming front. Ceilings will lower to 1200-2500 ft at all
terminals by 10z, with some indications of IFR ceilings will be
possible. Visibility generally 5-6+SM, though conditions could be
briefly lower in any heavier rain. Frontal passage occurs Monday
morning, bringing showers to an end, but ceilings will likely remain
MVFR through the end of the TAF period, with additional rain
possible Monday afternoon. S/SW winds to remain 6-12 kt with gusts
to around 20 kt through 00z, then gusts diminish overnight. However,
LLJ will result in LLWS of 35-40 kt at all terminals overnight, as
well. Winds will trend more toward the W after the frontal passage
on Monday morning.
Outlook...
Monday Night: VFR. Slight chance SHRA.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. Chance SHRA.
Wednesday Night: VFR. Chance SHRA, Slight chance TSRA.
Thursday: VFR. Chance SHRA, Chance TSRA.
Thursday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA, Slight chance TSRA.
Friday: Mainly VFR, with local IFR possible. Chance SHRA, Chance
TSRA.
&&
.MARINE...
As of 217 PM EDT Sunday...
A Lake Wind Advisory is in effect for the broad and northern
waters of Lake Champlain until 8 PM today. South winds ahead an
approaching frontal system will lead to increasing winds on Lake
Champlain enhancing gusts and wave conditions. Winds and gusts
on the lake will increase to 15 to 25 knots through this
afternoon. Waves will be generally 1 to 3 ft. Gusts will weaken
back to around 10 to 15 knots after sunset this evening.
&&
.CLIMATE...
As of 217 PM EDT Sunday...
Possible heavy rainfall tomorrow into Monday could approach
daily rainfall record levels. Below are the current daily
precipitation total records that may be broken at our area
climate sites.
Record Precipitation:
August 2:
KMSS: 1.31/2020
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
WHAT HAS CHANGED...Danzig
DISCUSSION...Danzig/Hastings
AVIATION...Hastings
MARINE...NWS BTV
CLIMATE...NWS BTV
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