459
FXUS61 KBTV 281913
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
313 PM EDT Sun Jun 28 2026

.WHAT HAS CHANGED...
As of 312 PM EDT Sunday...

Temperatures for Tuesday and Wednesday have been reduced slightly to
account for increased cloud cover and precipitation chances.
Dangerous heat still looks on track Wednesday through the holiday
weekend. The threat for severe weather has increased for Wednesday.

&&

.KEY MESSAGES...
As of 312 PM EDT Sunday...

1. Dangerous heat expected on Wednesday. Heat headlines will
likely be needed in the coming days.

2. Strong to severe thunderstorms possible Tuesday and
Wednesday.

3. Dangerously hot and humid conditions prevail into next
weekend with daily chances of scattered showers and thunderstorms
expected.

&&

.DISCUSSION...
As of 312 PM EDT Sunday...

KEY MESSAGE 1: We will see a gradual warming trend over the next
several days with temperature slowly approaching 90 degrees by
Tuesday afternoon across southern Vermont. The latest deterministic
and ensemble guidance has dropped temperature a few degrees Tuesday
afternoon as increased cloud cover and rain chances from a shortwave
trough moving overhead will coincide with peak heating.
Nevertheless, temperatures in the mid to upper 80s with dewpoints
climbing into the mid 60s can be expected. The jury is still out on
how warm Wednesday will be as cloud cover is expected to persist
across the region in the wake of widespread showers and
thunderstorms that will be exiting the region Wednesday morning.
This will initially stunt our diurnal heating which may limit our
ability to warm into the mid 90s. Another fly in the ointment will
be scattered to numerous showers and thunderstorms Wednesday
afternoon may also inhibit heating. The NBM thinks we could warm all
the way up to 97 degrees in the wider valleys on Wednesday but the
latest thinking is that we will likely be more in the 90-94 range
with the possibility of not even breaking 90 degrees in some areas.
Still, with dewpoints surging into the lower 70s Wednesday
afternoon, heat indices will climb between 95 and 103 for most, if
not all, locations. This would warrant the issuance of a heat
advisory if trends continue to show these heat indices and
confidence increases.

KEY MESSAGE 2: Surface high pressure will shift off to the east Tuesday
morning while we remain under the northern periphery of an
impressive 500 mb high pressure system. Models continue to keep the
center of the upper level high well to our south which will leave us
with northwesterly flow aloft. Several shortwave disturbances are
expected to move through the region on Tuesday and Wednesday with
scattered to numerous showers and thunderstorms. Tuesday will be the
tricky day as the shortwave timing will likely be during the evening
and overnight hours, thus limiting surface instability. The NAM and
GFS both show elevated thunderstorms capable of small hail and very
heavy rain but without these storms being rooted in the boundary
layer, it`s very likely we see any strong to severe wind gusts.
Nevertheless, it`s impressive to see what the models are showing
overnight as it`s not a typical set-up for some stronger
thunderstorms. Wednesday looks significantly more likely that we
could see severe weather across the Northeast. Temperatures at or
above 90 degrees, dewpoints near or above 70 degrees, and a strong
shortwave should all come together to produce a robust round of
thunderstorms during the afternoon hours. Models are showing CAPE
values between 1500 and 2000 J/kg and 0-6 km shear of 40-45 knots.
This is plenty for some supercells to develop so it`ll be worth
watching closely as Wednesday approaches.

KEY MESSAGE 3: Large scale synoptic pattern shows mid/upper lvl ridge
anchored over the central Appalachian Mtns thru most of the upcoming
week, while the westerly flow aloft with embedded s/w`s are progged
to be near the International Border. This expanding heat ridge wl
produce dangerously hot and humid conditions for Thurs and Friday,
with the peak of the conditions expected on Thurs. The latest heat
risk analysis shows widespread moderate to major impacts with
localized extreme values possible in the Champlain Valley on Thurs
and Friday, with slight improvement by Saturday. Current forecast by
WPC shows highs on Thurs upper 80s to mid 90s, with some localized
upper 90s expected near VSF, while dwpts are in the 60s, supporting
heat index values btwn 95 and 100 degrees. Similar type conditions
are forecasted by WPC for Friday, before cooler and slightly drier
air develops by next Saturday.

The chances for thunderstorms wl be closely associated with timing
of s/w energy in the westerly flow aloft for Thurs thru next
weekend. The expanding ridge axis on Thurs may push the strongest
dynamics along and north of the International Border, while mid lvl
cap is possible acrs most of our cwa. As better dynamics and
moisture arrive late Thurs into next weekend, the idea of
aftn/evening showers and storms looks reasonable. Given the progged
sfc based CAPE values in the 1500-2500 J/kg and 0-6km deep layer
shear of 30 to 40 knots, the potential for strong to severe storms
wl need to be watched. Also, the nw to se orientation of multiple
rounds of daily convection with favorable pw`s and high precip
efficiency (high precip rates), given the tall convective structure,
localized heavy rainfall and flash flooding will be possible too.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Through 18Z Monday...High pressure continues to build across our
taf sites this afternoon with VFR conditions and light terrain
driven winds under 6 knots. Given surface dewpoints are already
4 to 8 degrees lower this afternoon and another day removed from
precipitation, the probability of fog at MPV/SLK and EFK is <
20% at this time. Maybe a brief window of 20 to 40 minutes near
sunrise of IFR cigs/vis, but otherwise VFR conditions prevail
thru 18z Monday. Winds eventually turn to the south by Monday at
4 to 8 knots.

Outlook...

Monday Night: VFR. NO SIG WX.
Tuesday: VFR. Chance SHRA, Slight chance TSRA.
Tuesday Night: Mainly VFR, with areas MVFR possible. Chance SHRA,
Chance TSRA.
Wednesday: Mainly VFR, with local MVFR possible. Slight chance
SHRA, Slight chance TSRA.
Wednesday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA, Slight chance TSRA.
Thursday: Mainly VFR, with local MVFR possible. Slight chance
SHRA, Slight chance TSRA.
Thursday Night: VFR. Chance SHRA, Slight chance TSRA.
Friday: VFR. Chance SHRA, Chance TSRA.

&&

.CLIMATE...
Extreme heat and humidity is possible later this week,
especially on Wednesday and Thursday, which could lead to some
daily records. Below are the current daily high and low
temperature records in jeopardy at our area climate sites.

Record High Temperatures:

June 30:
KBTV: 93/2018

July 1:
KBTV: 96/2018
KMPV: 92/2018
KPBG: 94/1968
KMSS: 94/2018

July 2:
KBTV: 97/2018
KMPV: 90/2018
KMSS: 94/2018

July 3:
KMPV: 91/2002


Record High Minimum Temperatures:

July 1:
KBTV: 76/2018
KPBG: 73/1971
KSLK: 69/2018

July 2:
KPBG: 77/2002
KSLK: 68/2002

July 3:
KBTV: 76/1911
KPBG: 73/2002

July 4:
KPBG: 71/1973
KSLK: 67/1952

&&

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

&&

$$

WHAT HAS CHANGED...Clay
DISCUSSION...Clay/Taber
AVIATION...Taber
CLIMATE...NWS BTV