427
FXUS61 KBTV 292351
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
751 PM EDT Sat Jun 29 2024

.SYNOPSIS...
Steady rain is expected to continue through the afternoon hours with
a break in rainfall early this evening. Several rounds of convection
are expected tonight and again on Sunday which could produce a few
strong to locally severe storms. Very localized flash flooding also
remains possible with any convection tonight that moves over the
same area. A cold front on Sunday will put an end to rain and
thunderstorm chances with a dry start to July on tap for the North
Country.

&&

.NEAR TERM /THROUGH SUNDAY NIGHT/...
As of 745 PM EDT Saturday...Infrared satellite shows cloud top
cooling occurring across northern NY with GLM detecting a
couple of cloud flashes moments ago across southern Clinton
county. After an unseasonably cool late June day for North
Country standards, temperatures are not expected to drop all
that much and actually even rise a few degrees as warmer air
aloft is advected into our region in the next few hours.
Surface analysis shows the actual surface warm front still well
south of our area. While there are some subtle signs of
environmental destabilization, the expectation is that
thunderstorms that do develop this evening into the first half
of the overnight hours should be of garden variety, with
potential for torrential downpours given that the PWATs of 1.9
inches is near max of SPC sounding climatology for the Albany,
NY upper air site.

PREVIOUS DISCUSSION...Rainfall continues across the North
Country this afternoon as a warm front continues to push through
the North Country. There was a quick burst in isentropic
forcing west of the Adirondacks earlier that allowed for a
period of heavy rain which has since subsided. So far, rainfall
totals are on track with anywhere from a quarter of an inch in
Vermont upwards to an inch in northern New York. Rainfall
associated with the warm front will continue into the late
afternoon or early evening hours before we see a brief break in
rainfall. Some gradual destabilization is expected within the
warm sector, especially across northern New York, this evening
which is expected to act as a catalyst for additional showers
and thunderstorms. At this time, flooding looks unlikely given
the additional showers and storms will be rather scattered and
rainfall totals thus far haven`t been anything excessive.
However, we continue to monitor the potential for a wet
microburst or two this evening across northern new York. There
are some pros and cons for this potential which we will
highlight. Pros:
DCAPE near or in excess of 1000 J/kg, strong low level shear
profiles, and mid-level dry air entrainment. Cons: Potential capping
due to rain cooled air and lack of SBCAPE and MUCAPE. With that all
said, there could be enough negative buoyancy associated with the
DCAPE to punch through any cap briefly. It`ll be something to watch
for sure but remains a very conditional set-up.

As the sun begins to rise on Sunday, so will our severe
probabilities. We have an unusual set-up on Sunday where our severe
potential is expected to peak by late morning and end by mid-
afternoon. Our airmass tomorrow will be highlighted by a very moist
low level environment with a decent bit of dry in the mid and upper
levels. This dry air remains a concern as it is expected to limit
areal coverage of thunderstorms. A pre-frontal trough is expected to
act as a trigger Sunday morning but just how many thunderstorms
develop remains very questionable. We will have a very favorable
environment tomorrow morning which will be highlighted by 1500+ J/kg
of CAPE, 50-60 knots of 0-6 km shear, and upwards of 800-1000 J/kg
of DCAPE. There is a potential nothing happens tomorrow while there
is also the potential for several strong to severe thunderstorms.
All of the high-res CAMs show 1-3 storms in the aforementioned
environment which could be long-tracked and could be strong to
severe but disagree on the placement of the thunderstorms. It`s more
important, in this case in particular, to understand the forcing
mechanisms and the background environmental fields rather than
trying to see where any single CAM is trying to depict a storm.
Timing also remains a bit of uncertainty as the last several runs
have an early pre-frontal trough although some ensemble guidance
suggests a later passage. A later passage would increase severe
potential while earlier passage would decrease it. We will be
monitoring this and should have a much better idea come Sunday
morning.

Following the pre-frontal trough, we will see a cold front lag
around 3 hours behind which should help scour out the low level
moisture and humid conditions. Decreasing rain chances will be seen
late Sunday afternoon through the overnight hours with a few gusts
of winds from the northwest following the FROPA. Temperatures will
return to more seasonal values Sunday night following the FROPA
which will be appreciated as no one really likes 70 degree
dewpoints.

&&

.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 318 PM EDT Saturday...A cooler, drier airmass moves into the
region for Monday. Dew points will fall into the 50s and 40s by the
end of the day. There is the chance of an isolated shower over the
higher terrain of Vermont during the day, but with dry low levels
and marginal conditions, anything would be very light. There is no
threat for thunder. Temperatures drop back into the 40s and 50s
overnight, in what will be the coldest night of the week. The
boundary layer should decouple in many areas and the coldest hollows
could drop into the low 40s or maybe even upper 30s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 318 PM EDT Saturday...Ridging builds in from the south for
Tuesday and Wednesday, sending temperatures above normal and
bringing the humidity back. Dew points eventually rise into the 60s
and temperatures will rise into the 80s. A weakening cold front
passes into the region Wednesday night and will bring some showers
and possible embedded thunderstorms. The most likely solution is
that it passes through northern New York in the evening and through
Vermont around and after midnight. However, there is still decent
ensemble spread so put a lot of chance PoPs on either side for now
until confidence grows. While there is the chance of thunderstorms,
there is no severe risk. While the front will not bring in a dry
airmass behind it, it will shunt the ridge back to the south before
it can become entrenched over the area send the temperatures and
humidity to high levels. The formal front generally dissipates but
there will still be a bit of a boundary in place on Thursday. There
is the possibility that a few showers fire along this but anything
would be light and scattered. Overall, the shower threat for the
Fourth of July is decreasing and thunderstorms are also not expected
regardless. A region of low pressure looks to move into the region
for the weekend and bring more chances of showers.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Through 00Z Monday...MVFR ceilings are expected to continue
well into the overnight hours with increasing low level moisture
associated with a warm front. Rainfall has been pretty steady
during the daytime hours and has generally kept visibility in
the 3-5 SM range but brief deterioration to IFR visibilities
cannot be ruled out for the first few hours of the TAF period,
i.e. from Sunday 00z to 06z. In addition, LLWS of 45-50 kt at
around 2000 ft elevation will be in place across all terminals
through Sunday 06z. Additional chances for showers and
thunderstorms do exist this evening but questions remain how
widespread they would be. Currently, confidence is too low to
put in TSRA. Thunderstorm chances would once again be present
particularly between Sunday 09z and 16z but once again,
confidence in areal and temporal coverage is too low to put in
the TAFs. Overall, ceilings begin to improve in the Sunday 12 to
15z time frame on with VFR conditions expected everywhere
outside of showers and thunderstorms. From Sunday 18z onwards,
winds turn to the west northwest as a cold front crosses the
region with 15-25 kt gusts possible.

Outlook...

Sunday Night: VFR. Slight chance SHRA.
Monday: VFR. NO SIG WX.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. Slight chance SHRA, Slight chance TSRA.
Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA, Slight chance TSRA.
Independence Day: Mainly VFR, with local IFR possible. Slight
chance SHRA.

&&

.HYDROLOGY...
The threat for localized heavy downpours and isolated flash flooding
continues across our region although looks less likely than
before.  The Weather Prediction Center Day 1 Excessive Rainfall
Outlook has been reduced to just a 5% chance of rainfall
exceeding flash flood guidance within 25 miles of a given point.
We`ve generally seen between 0.25" and 1" of rain thus far with
the highest amounts of rain across St. Lawrence County. An
additional 0.25" to 1" of rain is expected through Sunday
afternoon but rainfall rates overall will likely not support
flash flooding. However, several round of showers and
thunderstorms are expected tonight and again on Sunday. Should
one location see several rounds of convection, the additional
rainfall coupled with what has already fallen may lead to
localized flash flooding.

&&

.MARINE...
Winds have begun to diminish across Lake Champlain with winds
generally in the 15 to 30 knot range. We did see some gusts over
40 knots this morning but we haven`t seen these in quite some
time. Waves should begin to slowly diminish as winds diminish
this evening with waves currently in the 2-4 ft range and will
diminish to 1-3 ft after midnight.

&&

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

&&

$$
SYNOPSIS...Clay
NEAR TERM...Chai/Clay
SHORT TERM...Myskowski
LONG TERM...Myskowski
AVIATION...Chai
HYDROLOGY...Clay
MARINE...Clay