-- Discussion containing changed information from previous version are highlighted. --
129
FXUS61 KBTV 131430
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
1030 AM EDT Thu Jun 13 2024

.SYNOPSIS...
A warm and increasingly breezy day is expected ahead of a cold
front that will slide southeast Friday. Showers and possibly
thunderstorms will occur along this feature late tonight into
Friday. Localized stronger storms will be possible in far
southern Vermont early Friday afternoon. Cool and dry air
filters in for the weekend. Then by Monday, warm and moist air
will shift back into the region. Temperatures warming into the
upper 80s to mid 90s is expected by the middle of next week. In
conjunction with high dewpoints and warm overnight conditions,
heat impacts are likely next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
-- Changed Discussion --
As of 1029 AM EDT Thursday...No significant changes needed to
the forecast right now as the previous forecast remains well on
track. Mostly sunny skies this morning will trend to partly
sunny with some mid/high clouds moving this afternoon ahead of
an approaching shortwave trough. Latest guidance still holds off
on any precip associated with this feature until after 00Z so
did adjust PoPs slightly to indicate nil chances for precip
through the daylight hours. The remainder of the forecast is
unchanged at this time.

Previous Discussion...A fairly quiet morning with temperatures
warming fast under blue sky and increasing south winds. Some fog
is still present in eastern Vermont, and will likely be gone in
about an hour as winds continue to slowly ramp up. Today will
be quiet for the most part. Increasing warmth and moisture as
surface high pressure moves east will result in upper 70s to mid
80s today. Although dewpoints will be climbing, values in the
mid 50s to lower 60s won`t be overly oppressive. There`s no real
forcing today, but it appears a capping inversion could briefly
be breakable with daytime heating. There`s a lot of 10 PoPs
across the region, as there could be a stray shower that
develop. Some fast winds will be developing aloft, and so
increasing southerly gusts are expected this afternoon, perhaps
even up to 30 to 35 mph in parts of the St. Lawrence Valley.

The better chances for rain will be from convection that
develops across Ontario Province that then slides eastwards late
this evening into the overnight hours. Showers and storms
should be in a broken line approaching the St. Lawrence Valley,
but loss of daytime heating and better dynamics lifting north of
the forecast area should see this convection on the decline.
Late Friday morning, increasing instability should allow
showers and storms to reintensify in conjunction with a vort max
ejecting northeastwards. Frontogenesis is expected to take
place and a cold front will strengthen as it moves across
southern Vermont Friday afternoon. This will be the window when
southern and central Vermont has the best chance for showers
and storms early Friday afternoon. With about 500-1000 J/kg of
CAPE and about 40-45 knots of 0-6km shear, there may be a small
window for strong to locally severe storms. However, better
dynamics are going to be tied to the intensifying front that
reaches peak intensity south of the region in Massachusetts and
far southern New Hampshire. The intensity of storms will be
conditional on clearing with the potential for lingering clouds
and rain from the prefrontal trough. And so SPC`s depiction of a
slight risk outlook outside our forecast area and a marginal
risk outlook at the southern fringe of Rutland and Windsor
Counties of Vermont appear reasonable. WPC has a marginal risk
for excessive rainfall covering almost the same region. Cooler
and drier northwest flow will lie behind the front, with most
topping out in the 70s to near 80, though possibly up to mid-80s
perhaps in the Connecticut River Valley.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 316 AM EDT Thursday...Any lingering showers and thunderstorms
exit to the east in the evening, with north winds picking up through
the night as much colder and drier air mass advects into the region.
925mb temperatures fall from +13C to +7C by daybreak, leading to a
spectacular Saturday with abundant sunshine and dew points in the
30s and 40s. The only fly in the ointment would be the steady north
winds. Forecast soundings suggest mixing up to 850mb, which would
help mix down 20 to 25 mph gusts. With 850mb temperatures around
+5C, highs will only top out in the 60s to near 70. The cooler
apparent temperatures should be balanced out by the full sunshine on
tap and the high sun angle, given that we are only several days away
from summer solstice. Winds should diminish quickly after sunset.
With clear skies and light winds and a 1020mb surface high building
into the region, it should be a good radiational cooling night with
widespread lows in the 40s, except upper 30s for the sheltered
colder hollows and low 50s for the immediate Champlain Valley.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 316 AM EDT Thursday...Father`s Day looks to be quite similar to
Saturday, with lighter winds and daytime highs in the 70s. Dew
points look to be a tad higher, but still generally in the 40s. Once
again, with abundant sunshine and comfortable humidity, get outside
and enjoy the gorgeous conditions. And if you haven`t already done
so, you might want to set aside some time to put in the window AC as
summer heat and humidity will be making a return during the work
week. Ensemble guidance shows good agreement that a 590+ Dm upper
ridge will build across the southeast U.S., allowing for summer heat
and humidity to be advected into our region. Daytime highs could
approach or exceed 90 degrees each day from Monday into Wednesday
with little nighttime relief. Some locations, including Burlington,
could see the first heatwave of the season, defined as three
consecutive days of 90+ degree high temperatures. With dew points in
the 60s, heat index values could be in the mid to upper 90 range,
especially on Tuesday and Wednesday. Once again, at this time frame
in the forecast cycle, the fly in the ointment would be the
development of thunderstorms. Given plenty of daytime instability
and the potential for somewhere in the Northeast to be on the
periphery of a building heat dome, there is the potential for strong
to severe thunderstorms to develop and ride up and over a crest of
high pressure. Whether or not your location can muster three
straight days of 90+ highs, or is being issued with Heat Advisories,
the new experimental WPC heat risk is now highlighting the growing
potential for moderate to major (level 2 to 3 out of 4) risks of
heat-related impacts on Tuesday and Wednesday next week. It is not
out of the question that if thunderstorms do hold off, heat index
values could even push 100 degrees for part of the Champlain Valley
and the St Lawrence Valley from a combination of air temperatures in
the low to mid 90s and dew points in the mid 60s to around 70. This
would result in a low but non-zero chance of extreme risk (level 4
of 4) of heat related impacts. Given that the major heat risk
category affects anyone without effective cooling and/or adequate
hydration, the public is encouraged to take preventative measures
such as having access to AC or minimizing vigorous outdoor
activities during the peak of the heat.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
Through 12Z Friday...Mainly VFR for the next 24 hours. South to
southwest winds will increase today. By 14 or 15z, most
locations should be 6 to 13 knots sustained with gusts 15 to 22
knots possible, with the highest gusts at KMSS and KBTV. About
00z-02z, faster flow aloft ahead of a boundary with 40 to 45
knot winds at 2000 ft agl are likely and noted LLWS at various
terminals. This boundary will also bring precipitation, but
lagging behind the faster flow, likely arriving near KMSS about
03z-04z then shifting east. Activity will be breaking up and so
mentioned prevailing SHRA at KMSS and VCSH eastwards. Some 3-5SM
visibility may take place in heavier showers, but not
anticipating widespread reductions from rain. Surface winds
remain elevated after 00z at about 5 to 10 knots.

Outlook...

Friday: VFR. Chance SHRA, Slight chance TSRA.
Friday Night: VFR. Slight chance SHRA.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: VFR. NO SIG WX.
Sunday Night: VFR. Slight chance SHRA.
Monday: VFR. NO SIG WX.

&&

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

&&

$$
SYNOPSIS...Haynes
NEAR TERM...Haynes/Lahiff
SHORT TERM...Chai
LONG TERM...Chai
AVIATION...Haynes