893
FXUS61 KBTV 010022
AFDBTV
Area Forecast Discussion
National Weather Service Burlington VT
822 PM EDT Tue Jun 30 2026
.WHAT HAS CHANGED...
As of 821 PM EDT Tuesday...Updated PoPs and adjusted areal
coverage of showers/storms overnight with gusty wind potl. See
Key message 2 below.
&&
.KEY MESSAGES...
As of 821 PM EDT Tuesday...
1. Major to localized extreme heat risk anticipated Wednesday
and Thursday 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 continue through
Friday, some localized strong to severe storms possible, especially
late tonight.
3. Dangerously hot and humid conditions will linger into the
holiday weekend along with daily chances of showers and
thunderstorms.
&&
.DISCUSSION...
As of 821 PM EDT Tuesday...
KEY MESSAGE 1: A long and dangerous heat wave is expected to impact the
fa from Weds into the upcoming holiday weekend, as a strong
mid/upper lvl heat ridge builds acrs the central Appalachian
Mountains. Progged 925mb temps are expected to be in the 26-28C
range for Weds and 27-30C on Thurs, which is 99th-100th percentile
for our cwa, indicating the significance of this upcoming heat wave.
In addition, 2m dwpts wl continue to climb tonight as convection
helps to saturate the bl, resulting in many areas seeing values in
the 68-75F range by Weds. Little mixing out of drier air is expected
during peak heating, so this wl create heat index values around 105F
in the warning area and 95 to 100F in the advisory. The warmest day
continues to be Thursday acrs our cwa with high temps in the lower
90s mtns to upper 90s to near 100F in the Champlain and Lower CT
River Valleys. A few record high temps are likely to be broken
during this heat wave. The boundary layer moisture wl result in very
muggy conditions overnight with lows upper 60s to upper 70s most
nights. These very warm and muggy conditions wl provide little
relief at night, especially wider valleys.
KEY MESSAGE 2: Updated PoPs and shower/thunderstorm coverage
area overnight at 800 pm based on MCS track across ON/QE this
evening. Earlier TYX scans had echo tops to between 65-70 kft
per coord. with Toronto Wx/EC - quite impressive. Feel MCS will
continue to drop SSE overnight per instability gradient
over/just west of our region. As such, based on current track
have updated PoPs to categorical for a period of time overnight,
and mentioned gusty winds, mainly from the Champlain Valley
west. Some training and possible localized flash flooding could
be possible in areas across the Dacks where persistent heavy
rainfall occurs overnight, but confidence is low at this time.
Prior discussion on convective potential from earlier this
afternoon is below...
Prior discussion...Very challenging fcst with regards to
thunderstorm potential and intensity tonight through Friday. SPC
has upgraded most of our cwa to slight risk (2 out of 5) for
severe on Thurs with 15% wind and marginal risk for excessive
rainfall continues by WPC.
GOES-19 mid lvl water vapor imagery shows our next embedded s/w
energy and moisture north of the Great Lakes, diving southeast
toward the Ottawa Valley. This energy is expected to arrive around
midnight for the SLV and into the CPV by early Weds morning. The
elevated convective parameters are impressive with MU CAPE values
btwn 1200-1800 J/kg, along with a very well defined EML moving
directly overhead at 06z. This is associated with impressive waa and
very sharp sw to ne instability gradient acrs our cwa tonight. The
idea of a cluster of strong to locally severe thunderstorms are very
much possible overnight with damaging winds the primary svr wx
threat. We could see a very similar scenario to this aftn`s
convective that is occurring just south of our cwa overnight tonight
acrs our cwa. Anybody camping outdoors overnight tonight should
monitor the weather closely and be ready to take shelter if storms
threaten.
The heat and humidity wl create daily CAPE values in the 2000-3000
J/kg acrs our cwa with 0 to 6 km deep layer shear around 30 knts.
However, better shear in the 40 to 50 knt range arrives along the
International Border area by Thurs aftn. Our thinking for Weds is
more trrn showers and thunderstorms are likely with some localized
threat for severe possible, given the large CAPE values. The
synoptic scale ascent on Weds and Thurs is much less with weaker
dynamics/short wave energy, but instability wl be greater. Thinking
primary convective mode would be pulse-like, evolving into mini-
bowing line segments with localized damaging winds as the main
threat, followed by hail. SPC has upgraded our entire cwa to slight
risk for severe (2 out of 5). Additional threat for strong to severe
storms are possible on Thurs and Friday, but overall coverage and
intensity is difficult to determine at this time.
KEY MESSAGE 3: Heading into the weekend, warm weather lingers although
temperatures and heat indices will not be as warm as the previous
days. Current forecast shows temperatures reaching the 80s areawide,
with temperatures trending cooler heading into the start of next
week. Overnight lows remain warm, generally in the 60s, which may
lead to accumulating heat impacts. There are 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.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...VFR with mixed MVFR overnight as area of
showers, and heavier cluster of storms tracks near/just west of
the area. Main threat of stronger storms and assoc. turbulence
to generally occur from the Champlain Valley west in the 02-08Z
time frame, but threat is conditional and confidence only modest
at best for any one terminal to experience a stronger storm.
Strong, gusty winds and severe turbulence in the vicinity of any
storms will be a possibility overnight. Showers/storms mainly
clear southeast by sunrise Wednesday leaving VFR conditions area
wide by later in the morning/afternoon. Winds generally light
southerly 5-10 kts through the forecast period outside any
convection.
Outlook...
Wednesday Night: VFR. Slight chance SHRA, Slight chance TSRA.
Thursday: VFR. Chance SHRA, Chance TSRA.
Thursday Night: VFR. Chance SHRA, 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,
Slight 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:
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...JMG/Neiles/Taber
AVIATION...JMG
CLIMATE...NWS BTV
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