231
FXUS61 KBTV 270649
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
249 AM EDT Mon Jul 27 2026
.WHAT HAS CHANGED...
As of 243 AM EDT Monday...
Confidence has increased in the potential for heavier downpours
and localized flash flooding on both Tuesday and Wednesday. Area
of highest concern is northern New York, but any spot that sees
multiple days of heavy rain will need to be monitored.
Based on latest model trends, have incorporated a sharper
gradient of precipitation chances and amounts Tuesday and
Wednesday due to the main axis of moisture and instability over
New York on Tuesday as well as southeasterly and easterly
downsloping on Wednesday.
&&
.KEY MESSAGES...
As of 243 AM EDT Monday...
1. Scattered showers and thunderstorms are expected this
afternoon, mainly across the Adirondacks, featuring occasional
heavy downpours.
2. More widespread showers and thunderstorms are expected
Tuesday through Thursday as a slow moving system tracks through
the region through the midweek, bringing the potential for
localized flash flooding.
3. An unsettled weather pattern prevails late week into next
weekend as departing system is replaced by another developing
mid/upper level trof.
&&
.DISCUSSION...
As of 243 AM EDT Monday...
KEY MESSAGE 1: Surface high pressure is currently stationed across the
Ohio Valley early this morning with upper level troughing directly
overhead northern New York and Vermont. Throughout the night,
temperatures are expected to fall into the mid 50s to mid 60s. This
will also bring the potential for patchy valley fog, especially in
Adirondack locations that received rainfall yesterday (portions of
western Adacks reported 0.50-1.50 inches). Throughout the day
today, troughing will slide east of the region, but we should
have enough shortwave energy, moisture, and warmth to allow for
some showers and thunderstorms, about 25-65% chance in northern
New York, highest in the northern Adirondacks. For Vermont,
chances are lower in general, around 5-40%, and mainly in the
Greens or from any precip that forms in the Adirondacks and
holds together as it drifts eastward. Should the New York
locations that received sufficient rainfall yesterday (these
areas may include Hogansburg, Brasher, Tupper Lake, Parishville,
Horseshoe Lake, South Bombay, Stark, and eastern Potsdam)
receive another round or two of showers or thunderstorms today
we`ll need to monitor these areas for potential flash flooding,
but this threat is highly conditional. The Weather Prediction
Center currently has most of northern New York, outside of the
Champlain Valley, under a Marginal Risk (Risk level 1 out of 4;
5% chance for rainfall exceeding flash flood guidance) for
today. Northern New York rivers could see some small rises, but
nothing near bankfull with the recent dryness we have had.
Temperatures today will be in the upper 70s to mid 80s, slightly
above seasonal normals. Tonight, shower activity should dwindle
again like yesterday, and lows will be relatively mild in the
mid 50s to mid 60s. Total precipitation amounts will be around
0.10-0.25" in the Adirondacks and parts of the Greens, locally
higher in heavy, slow moving storms.
KEY MESSAGE 2: A slow moving upper low is expected to track through the
region midweek, bringing chances of persistent showery weather
Tuesday through Thursday. On Tuesday, models place the upper low
somewhere from the southern Ontario-Quebec line to central New York,
and its associated surface low pressure around eastern Lake Ontario
and central New York. This multi-layer low pressure is expected to
move very little Tuesday and Tuesday night, spinning cyclonically
over the Northeast and drifting slightly eastward. As it does so, it
will send plumes of moisture into our area, resulting in
widespread showers and thunderstorms likely for northern New
York and southern Vermont. Northern Vermont is a little less
certain, with several models keeping the main slug of rain from
reaching the Vermont- Canada border and Northeast Kingdom,
largely due to downsloping off the Green Mountains with a
southeasterly flow. The main moisture and instability looks to
be stationed over New York, with ridging anchored over Maine.
Tuesday will also be one more chance for temperatures to reach
the upper 70s and 80s before the system wicks away our warmth,
which will help fuel any thunderstorms. Models are suggesting
Pwats could reach as high as 1.75-2.00 inches in some locations,
and surface instability runs around 1500 J/kg, producing tall,
skinny CAPE soundings. At times, storm motions look to run under
10 knots, indicating any showers or storms could be slow
moving, heavy rainers. Forecast additional precipitation amounts
from early Tuesday morning into late Tuesday night will be as
high as 0.50-1.00" Adirondacks and west as well as portions of
southern Vermont. For the northern Champlain Valley as well as
northern Vermont and southeastern Vermont, we`re looking at
closer to 0.05- 0.50". At the moment, the most likely 24 hour
period for the St. Lawrence Valley to get 1 inch is Tuesday and
Tuesday night. Any areas that see heavier downpours today will
need to be especially watched on Tuesday. The WPC has a Marginal
(at least 5%) Risk of excessive rainfall over the entire
forecast area Tuesday.
On Wednesday, the multi-layer low pressure swings southeast into the
mid-Atlantic, continuing southeasterly to even easterly flow at
times across the forecast area. Precipitation continues to look more
likely in southern portions of the forecast area with downsloping in
the wider valleys, and we lose the majority of instability. Our
highs only reaching the upper 60s to mid 70s, we won`t see the same
convective showers and storms that we`re expecting Tuesday. Still,
steadier rain could produce as much as 0.75-1.25" of additional rain
in southern Vermont, with 0.30-0.75" elsewhere. Wednesday is another
period that the WPC has our entire area under Marginal Risk of
excessive rainfall. River rises will be expected by Wednesday night
following the bulk of the precipitation. At the moment, the most
likely period of 1 inch within 24 hours for most of the area falls
from Tuesday night to Wednesday, though southeastern Vermont could
make out especially well Wednesday-Wednesday night in southeasterly
flow. Once again, locations that receive heavy rain today or Tuesday
will need to be closely monitored on Wednesday. Lingering showers
and thunderstorms are also likely on Thursday as the upper level
trough slowly exits the region and the occluded surface low remains
nearby while temperatures rebound slightly into the 70s. Most likely
location of any lingering showers or thunderstorms on Thursday will
be eastern Vermont, closest to forcing.
KEY MESSAGE 3: An unsettled weather pattern continues for late week
into next weekend as first system slowly departs by Friday, before
another one arrives late Sat into Sunday. Still a large spread in
timing of each system, especially toward next weekend, but cutoff
and closed 7-5h circulation, feel the potential for showers wl
linger into Friday associated with initial trof and weakening area
of low pres. ECMWF shows weak differential heating boundary with
some instability progged acrs northern NY/Champlain Valley, while
deeper moisture/clouds linger over VT on Friday. This convergence
and instability wl support a the threat for showers and embedded
storms on Friday.
Weak ridge tries to build into our cwa for Saturday, before next s/w
and associated energy arrives late Saturday into Sunday. The
evolution and track of 700-500mb trof, along with associated sfc low
pres wl determine placement and areal coverage of showers/storms for
this upcoming weekend. Latest guidances shows Saturday highest
potential over northern NY, while Sunday activity wl be more
widespread impacting both VT and NY. Limited run to run continuity
and large spread in potential solutions results in low forecaster
confidence and associated predictability on probability and timing
of precip, especially Sunday into early next week. Temps wl be
driven by clouds/precip, but mostly above normal values anticipated,
especially at night with lows in the upper 50s to upper 60s, while
highs range from the mid 70s to mid 80s. Some levels of humidity are
expected, but the probability of much above normal temps or
significant heat is low given anticipated pattern.
&&
.AVIATION /06Z MONDAY THROUGH FRIDAY/...
Through 06Z Tuesday...Aviation challenge is duration of fog at
SLK and potential fog development at MPV. Currently LIFR in fog
at SLK, but conditions have been bouncing between LIFR and VFR
as mid level clouds are impacting SLK. Thinking mostly
prevailing LIFR in fog thru 08-09z, before additional clouds
will produce intervals of IFR or lower conditions at SLK and
improving to VFR by 11z. MPV thinking a brief window of IFR or
lower conditions are possible between 09-11z. Otherwise, VFR
conditions prevail at the rest of our sites with light terrain
driven winds, becoming south/southwest 3 to 7 knots by mid
morning.
Outlook...
Tuesday: VFR. Chance SHRA, Chance TSRA.
Tuesday Night: Mainly VFR, with local IFR possible. Chance SHRA,
Slight chance TSRA.
Wednesday: MVFR/IFR conditions possible. Definite SHRA, Chance
TSRA.
Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA.
Thursday: Mainly MVFR, with areas IFR possible. Likely SHRA,
Slight chance TSRA.
Thursday Night: Mainly MVFR, with local IFR possible. Slight
chance SHRA, Slight chance TSRA.
Friday: MVFR/IFR conditions possible. Slight chance SHRA, Slight
chance TSRA.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
WHAT HAS CHANGED...Storm
DISCUSSION...Storm/Taber
AVIATION...Taber
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