970
FXUS61 KBTV 301719
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
119 PM EDT Tue Jun 30 2026
.WHAT HAS CHANGED...
As of 117 PM EDT Tuesday...
Updated to include severe thunderstorm watch for St Lawrence
County and upgraded Excessive Heat Watch to Excessive Heat
Warning and Heat Advisory for the rest of the area. A complete
discussion will be issued by 4 PM with all the details.
&&
.KEY MESSAGES...
As of 223 AM EDT Tuesday...
1. Major to localized extreme heat risk expected Wednesday thru
Friday with heat index values near 105 degrees possible in the
Champlain Valley/Eastern Windsor and 95 to 100 elsewhere.
2. Daily chances for showers and thunderstorms increase today
and continue through Friday, with some localized strong to severe
storms possible.
3. Dangerously hot and humid conditions will linger into the
holiday weekend along with daily chances of showers and
thunderstorms.
&&
.DISCUSSION...
As of 223 AM EDT Tuesday...
KEY MESSAGE 1: Ridging builds into the region from the west for middle
and late week, with surface high pressure centering over the mid-
south. This will cause multiple days of southwest flow and allow an
area of significant heat to become established in the region. This
will be aided by an unseasonably strong area of low pressure across
the Great Plains. The ridge looks to remain in place at least
through Friday, before it finally looks to get shunted to the south
on Saturday. The peak of the highest heat indices looks to be on
Wednesday and Thursday, with the former having the highest dew
points and the latter likely having the highest temperatures. There
will be a couple factors that could potentially mitigate the worst
of the heat, but despite those, there is high confidence of
impactful heat from Wednesday through Friday. The first factor is
the potential for showers and thunderstorms each day, which would
drop temperatures and provide clouds to minimize solar heating.
Daily ridge runners look to pass around the periphery of the high,
and even if they remain to the north over Quebec or to the west over
western New York, there will still be convective debris carried into
the region by the upper level westerly flow. The other is the exact
placement of the high, mostly affecting Friday. Guidance is still
split on the exact end of this heat event, and there is still a low
possibility that the high retreats to the southwest enough during
the day that the worst of the heat remains to the south, though well
above average conditions would prevail. Overall, heat indices in
the 95-100 range are forecast for most places, with heat indices to
around 105 in the Champlain and Lower Connecticut River valleys.
Overnight lows around and above 70 will provide minimal relief and
the duration will cause cumulative effects.
KEY MESSAGE 2: The region will be on the northeastern extent of a large
ridge of high pressure, with the surface high centered well to the
south over the middle south. This puts us in the prime area for
ridge runners as they round the top of the high over the Great Lakes
and begin to dive southeast. An elevated mixed layer will become
established on Wednesday and continue into Thursday, but as is
typical, despite a few thousand joules of CAPE, capping will try to
prevent any convection from forming. However, the shortwaves should
provide enough forcing to overcome this and set off some
thunderstorms. The first MCS is currently over Lake Huron and will
move southeast today, though guidance has thankfully been trending
toward sending the strongest convection south too quickly and
keeping it to the west. The main area to watch for strong to severe
storms looks to be St. Lawrence County. There is no model
consistency for Wednesday through Friday, but there are also no
signals of continuous convection. Even after the current MCS
formed, most model guidance was not even initializing it for a
couple runs. Additional synoptic forcing from a cold front on
Saturday could lead to the most widespread showers and storms.
Overall, adequate 0-6 KM shear and CAPE will be present all week,
but the cap and placement of the ridge will be acting against the
severe potential. Isolated to scattered strong to severe storms will
be possible any day due to the environment, but they will be very
conditional. The biggest hazard with any of these storms would be
damaging winds.
KEY MESSAGE 3: Heading into the weekend, warm weather looks to linger
although temperatures and heat indices will not be as warm as the
week above. Current forecast shows temperatures generally in the 80s
areawide, with temperatures gradually trending cooler heading into
the start of next week. Overnight lows look to remain on the w armer
side, generally in the 60s, which may lead to accumulating heat
impacts. Although it looks like it won`t be quite as hot as earlier
in the week, it is important to remember to drink water and take
frequent breaks if working outside, especially with such an extended
period of warmer weather. There looks to be chances for showers and
thunderstorms throughout the weekend with the proximity of the
frontal boundary moving through the area, which may also help keep
temperatures cooler. There continues to be a lot of uncertainty in
this time range in regards to precipitation chances heading into
next week, with a wide range of model solutions at this time.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Through 12Z Wednesday...VFR conditions continue to prevail at all
terminals, and will continue through much of the forecast period
with a few high clouds overhead. Winds continue to remain light and
variable, trending more southerly after 12Z. There continues to
be some uncertainty in regards to convective development and
possible showers and thunderstorms after 18Z, but given the
uncertainty they have been left out of the forecast for now. If
any showers and thunderstorms do develop late in the forecast,
brief periods of MVFR and possibly IFR would be possible if
overhead, but VFR will generally prevail. Some MVFR ceilings may
develop towards the end of the forecast period, after 06Z or so,
but there is still a lot of uncertainty in how low ceilings will
trend.
Outlook...
Wednesday Night: VFR. Chance SHRA, Slight chance TSRA.
Thursday: VFR. Chance SHRA, Chance TSRA.
Thursday Night: VFR. Slight chance SHRA, Slight chance TSRA.
Friday: VFR. Slight chance SHRA, Slight chance TSRA.
Friday Night: VFR. Slight chance SHRA, Slight chance TSRA.
Independence Day: VFR. Chance SHRA, Chance TSRA.
Saturday Night: VFR. Slight chance SHRA.
Sunday: Mainly VFR, with local MVFR possible. Slight chance SHRA.
&&
.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...Heat Advisory from noon Wednesday to 7 PM EDT Friday for
VTZ003-004-006>008-010-016>020.
Extreme Heat Warning from noon Wednesday to 7 PM EDT Friday
for VTZ001-002-005-009-011-021.
NY...Heat Advisory from noon Wednesday to 7 PM EDT Friday for
NYZ026-027-029>031-034-087.
Extreme Heat Warning from noon Wednesday to 7 PM EDT Friday
for NYZ028-035.
&&
$$
WHAT HAS CHANGED...Taber
DISCUSSION...Kremer/Myskowski
AVIATION...Kremer
CLIMATE...NWS BTV
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