119
FXUS61 KBTV 161736
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
136 PM EDT Tue Jul 16 2024

.SYNOPSIS...
Heat will remain the rule for a couple more days until a cold front
reaches the area on Wednesday afternoon. Another round of showers
and thunderstorms will move through the region late this afternoon
into the evening. Some of the storms may be strong, with gusty winds
and heavy rainfall. Following one last round of showers with a cold
front Wednesday evening, cooler and drier weather is expected for
the end of the week and into the weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 130 PM EDT Tuesday...Convection is firing across northern
New York with some impressive cells. It`ll ride into an airmass
of greater instability and begin to organize. Despite our
weaker instability here, low level dry air should reinforce the
tendency for strong winds south. Our Severe Thunderstorm Watch
is being queued up and we will have it out the door soon.

Previous discussion...Precipitation should exit into NH/Quebec
early this morning, and expect we`ll see a period of subsidence
and dry weather as we await our next system, a vigorous
shortwave which is currently producing a MCS over eastern MI.
This feature will slide eastward through the early morning
hours, gradually weakening as it does so. The question will be
how much we can destabilize before it arrives later this
afternoon. Current expectations are that we`ll see at least some
breaks in the mid/high clouds, helping to warm temperatures
into low 80s to low 90s, with a few locations in the wider
valleys approaching 95F. Combined with dewpoints well into the
60s to near 70F, it will be another hot and humid day,
especially in the Champlain and lower CT River Valleys, where
heat index values will be in the lower to mid 90s. Hence the
Heat Advisory for these locations remain in place until 8 pm
this evening.

The aforementioned decaying MCS/MCV will serve as a focus for
another round of showers and thunderstorms to develop over Ontario
later this morning, which will then translate eastward into the
afternoon hours. Consensus of the latest hi-res CAM runs shows this
convection moving off eastern Lake Ontario by mid/late afternoon,
and reaching the Champlain Valley roughly 6-8 pm. Meanwhile, shear
will increase ahead of an incoming upper trough, with 0-6km values
of 35-45 kt by this evening. Current indications are that the
strongest activity will slide across mainly central and southern
sections of our region, along and south of a line extending from
Ogdensburg to Charlotte to St Johnsbury. Strong winds will be
possible with the stronger cores, potentially forming into a broken
line bowing segments. Note that SPC has adjusted their Slight Risk
(level 2 out of 5) in their Day 1 Thunderstorm Outlook, keeping it
limited to mainly south-central VT, while the remainder of the
region is included in the Marginal Risk. The other concern will be
heavy rain, as PWATs will approach or even exceed 2 inches ahead of
this convection. While it should have good forward motion, intense
rainfall rates are likely due to efficient rainfall processes and
deep warm cloud depths in excess of 12 kft. Many areas remain
susceptible to flash flooding due to recent rainfall; indeed, some
locations such as Addison, Washington, and Lamoille Counties have
flash flood guidance as low as 1-1.5 inches in an hour, and 1.5-2
inches in 3 hours. As mentioned above, it looks like the heaviest
rain will remain over central and southern portions of our forecast
area, which have a bit more breathing room. However, the
aforementioned locations will need to be watched closely as it will
not take much for additional flash flooding, even if they remain
just outside of the heaviest storm cores. WPC continues to keep
areas from the Greens westward included in the Marginal Risk (level
1 out of 4) in their Day 1 Excessive Rainfall Outlook. Showers and
storms will quickly exit to the east by midnight or so tonight,
leaving behind another warm, muggy night.

For Wednesday...still some uncertainty as to how things will play
out with an upper trough digging to our west, lifting a surface low
through Ontario/Quebec. The question is how quickly the attendant
cold front and potential pre-frontal trough cross our region. As
with today, there will be ample moisture pooling ahead of the front
with PWATs once again approaching 2 inches. CAPE may be somewhat
limited due to poor mid-level lapse rates across much of our region;
the best instability looks to remain just to our southeast, but
still anticipate enough buoyancy/forcing for storms to develop
during the afternoon hours. Like today, main threats would be gusty
winds and heavy rainfall. We continue to be included in a Marginal
Risk (1 out of 5) for severe thunderstorms in SPC`s Day 2 outlook.
WPC`s Day 2 Excessive Rainfall Outlook keeps the Marginal Risk (1
out of 4) just to our south, but given how things will be primed
after a couple of rounds of heavy rain, isolated flash flooding
cannot be completely ruled out. Temperatures will be a little cooler
than the previous couple of days, but still fairly muggy with highs
in the upper 70s to upper 80s.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY/...
As of 355 AM EDT Tuesday...Some residual showers can be expected
Wednesday night, though drier air moving into the area will result
in decreasing precipitation rates. Best chance for some continued
overnight showers will be in Vermont, where a moisture boundary
will remain draped overhead during the overnight hours. With the
loss of diurnal instability, showers will be scattered in
nature but can`t rule out some early night embedded rumbles of
thunder. Overnight lows will be in the 60s for most areas, and
into the mid to upper 50s locally over the northern Adirondacks.

The moisture boundary over Vermont will clear the area by Thursday
morning, allowing for drier air to work in from the northwest.
Dewpoints Thursday will be noticeably lower than Wednesday`s, and
high temperatures will range from the low 70s to low 80s. An upper-
level shortwave dropping through will provide scattered clouds and
maybe an isolated shower or two...though afternoon shower potential
is capped in the 10-20 percent range. Some breezy afternoon
west/northwest winds with gusts in the 10-15 mph range are expected.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
As of 355 AM EDT Tuesday...The work week will close out with
expansive surface high pressure building to our west, which will
provide tranquil weather conditions for Friday and Saturday. With
the center of the anticyclone located over the midwest, our forecast
area will see refreshing northwesterly flow. High temperatures will
be in the 70s to mid 80s, with dewpoints in the 50s.

Saturday night into Sunday brings a slight chance of showers as a
cold front drops through, followed by another shot of cooler air to
start next week. Given overall lack of moisture, the passage of the
cold front will be largely uneventful with just some isolated to
scattered showers expected. Highs Sunday will be in the 70s to low
80s, with a gradual warning trend through Tuesday. On continued
northwesterly flow, no oppressive humidity on the horizon.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Through 18Z Wednesday...Currently VFR with southwest winds of 5
to 11 knots and a few gusts of 16 to 20 knots. A compact weather
system upstream will produce a line of showers and storms
lifting into the area between about 19z and 01z. Have noted
TEMPOs with 2-4SM TSRA. There may be gusty winds in storms, and
think the highest chance will be at KRUT, where gusts up to 24
knots in the storms are noted, but if it takes a direct hit,
those gusts could be higher. Winds could briefly go west behind
the storms, but should trend back towards the southwest or
become terrain driven at 5 knots or less. Some fog may develop,
but there is some flow just above the surface. For now, have
elected to show 3-4SM BR at KMSS, KSLK, and KMPV. There should
be some 1500-2500 ft agl ceilings behind the precipitation, that
will lift or scatter out beyond 10z. Conditions should be VFR
about 12-14z Wednesday. Additional shower activity is like in
Vermont past 16z Wednesday.

Outlook...

Wednesday Night: VFR. Slight chance SHRA.
Thursday: VFR. Slight chance SHRA.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: VFR. NO SIG WX.
Sunday: Mainly VFR, with local MVFR possible. Slight chance SHRA.

&&

.BTV WATCHES/WARNINGS/ADVISORIES...
VT...Heat Advisory until 8 PM EDT this evening for VTZ005-009-011-
     021.
NY...Heat Advisory until 8 PM EDT this evening for NYZ035.

&&

$$
SYNOPSIS...Hastings
NEAR TERM...Hastings/Haynes
SHORT TERM...Duell
LONG TERM...Duell
AVIATION...Hastings