567
FXUS61 KBTV 282348
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
748 PM EDT Fri Jun 28 2024

.SYNOPSIS...
We hope you were able to enjoy the sunshine today or will be
able to as we have a very wet and windy weekend on tap for the
North Country. Rainfall associated with a warm front will
overspread the region Saturday morning with a brief break in
rain before several rounds of showers and thunderstorms are seen
Saturday night through Sunday morning. A cold front will bring
an end to the rain Sunday evening with seasonal and dry weather
on tap to start off July.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 736 PM EDT Friday...No big tweaks needed for the evening
update. Slightly adjusted clouds based on satellite
observations, but the forecast is running smoothly. Have a great
night!

We`ve got a quiet afternoon and evening on tap with high
pressure currently residing overhead. A few fair weather cumulus
have formed along the higher terrain this afternoon but a
plethora of dry air in the low levels will prevent any shower
activity through the first half of the overnight hours. After
midnight, rain chances will begin to creep up along the St.
Lawrence River as the leading edge of a warm front begins to
move into the region. By Sunrise on Saturday, rain is expected
throughout the St. Lawrence Valley but won`t be until later
Sunday that rain pushes eastward.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 259 PM EDT Friday...We`ve got an active weekend on tap with
both the potential for flash flooding, strong to locally severe
thunderstorms, and gusty winds up to 45 mph. We`re going to break
the weekend down into several sections that will highlight each
threat individually below.

Flash Flooding Potential...As a warm front tracks across the region
Saturday morning, we will see PWATs and dewpoints surge throughout
the day. The latest consensus on high-res models and ensembles is
that PWAT values will increase to 2-2.25" by mid-afternoon Saturday
as dewpoints approach 70 degrees. Quite the difference from the dry
conditions seen today. The models remain quite aggressive with the
isentropic lift accompanying the warm front which is expected to
yield some impressive rainfall totals across the region (more on
this in a moment). Following the period of isentropic lift, a brief
break in rainfall is expected prior to another round (possibly
several) of convection developing in the afternoon/evening which
could drop locally heavy rainfall. It appears thunderstorms won`t
develop until the round of convection in the afternoon/evening given
the stability that comes with a warm frontal passage which should
initially limit rainfall rates. When all is said and done, we are
looking at a widespread 0.50" to 1.00" of rainfall with the warm
frontal passage but amounts with the convection later in the day on
Saturday remain clouded as any once cell could produce very heavy
rainfall. The only downside to the heavy rain potential is that the
low level jet will be between 45 and 60 knots which will allow
storms to move very quickly across our forecast area. With recent
rainfall and additional early morning rainfall, any convective
bursts in the afternoon and evening could create some localized
flash flooding. Areal coverage isn`t enough to warrant a watch but
the threat continues to exist so be sure to stay weather aware.

Severe Weather Potential...There will be two periods where we could
see strong to severe storms. The first period will be Saturday
evening (mainly between 8 PM and 2 AM Sunday) as a strong shortwave
on the leading edge of the upper level trough will allow for better
synoptic lift. Surprisingly, the break in rainfall in the afternoon
is expected to allow for some weak destabilization that should
continue into the evening. With better upper level support, guidance
shows a round of thunderstorms moving through the area overnight.
Normally, overnight convection isn`t anything to worry about but
models are now suggesting upwards of 1000 J/kg of DCAPE while
soundings show near textbook wet microburst signatures. The main
question will be the stability of the boundary layer following
sunset but some strong to locally severe storms will be possible
Saturday night into early Sunday morning.

The second round will come Sunday afternoon with a pre-frontal
trough moving through a rapidly destabilizing environment. While
some of the high-res guidance may be a little over zealous with CAPE
values, we could see both SB and MLCAPE approach or exceed 1500-2000
J/kg. With deep layer shear still in place, we could see a broken
line of thunderstorms develop Sunday afternoon and push west to
east. This is a more recent development and it`ll be interesting to
watch future runs of numerical guidance to see if the severe threat
is able to materialize given the cold front is about 3 hours behind
the pre-frontal trough. More on this tomorrow.

Gusty Wind Potential...An unusually strong low level jet is expected
on Saturday that is likely to coincide with the passage of the warm
front. Winds at 850 mb will be upwards of 60 knots but we are
unlikely to mix these winds down to the surface given rain cooled
air creating a stable boundary layer. However, we could see some
downsloping on the northern slopes of the Adirondacks which could
allow for places like Malone to gust up to 45 mph. The Champlain and
St. Lawrence Valleys will see channeled southerly to southwesterly
flow which will allow for localized wind gusts up to 40 mph.
Elsewhere, the combination of terrain and rain cooled air should cap
winds gusts to below 35 mph. Nevertheless, it`ll be breezy so be
sure to secure any lawn furniture that may blow around.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 259 PM EDT Friday...Ridging will build in for the first part of
the week before a boundary sets up near the region toward the end of
the week, pushing the ridge and increasing heat/humidity to the
south but keeping the drier/cooler air to the north. There is high
ensemble agreement that shifts in this boundary placement would not
bring too much of a change in the weather. Monday should be mostly
dry though a weak terrain induced shower cannot be ruled out over
Vermont. Temperatures will be slightly below normal with low
humidity. Temperatures rise above normal with increasing humidity
for the rest of the week. However, the highest heat and humidity
will be kept to the south. A cold front approaches the region mid-
week but stalls and falls apart. This will provide the lift for some
showers and possible thunderstorms to develop on Wednesday-Friday
though none of these look to substantial, but the exact timing of
the highest shower chances remains to be seen. However, most of the
time it will be dry. Therefore, went with a lot of slight chance and
chance PoPs during this time. None of the rain looks heavy and
consistent enough to cause much of a hydro threat and there does not
look to be enough instability to cause much of a severe threat.
Going out farther, while temperatures may be a bit above normal, the
ridge responsible for the high heat and humidity looks to remain
suppressed to the south for some time.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
Through 00Z Sunday...All terminals are VFR for the next 12 hours.
Rain arrives between about 10-12z and will be spotty as low
level dry air gets mixed out followed some breaks before more
areawide activity shifts from southeast to northeast about 15z
Saturday. Most rain should not inhibit visibility much initially,
but after 15z, pockets of reduced visibility will be possible
in embedded areas of heavier rain. For now, have indicated 4-6SM
visibilities, but some lower observations will be possible.
Ceilings will begin to lower with heavier rain as well,
generally down to 1500-3500 ft agl. Winds will trend southerly
around 5 knots through 08z and then begin to increase towards 10
to 15 knots sustained and gusting 18 to 25 knots. Channeled
south winds will likely result in intermittent 30 knot gusts at
KBTV and downslope gusts to 30 knots at KSLK. At 2000 ft agl,
increasing south to southwest winds of 45 to 50 knots
necessitates some LLWS potentially as early as 15z, but mainly
after 20z, across terminals and will likely continue until the
low-level jet moves east sometime after 00z Sunday. Beyond 00z,
we will be monitoring the potential for nighttime convection
with heavy rain possible.

Outlook...

Saturday Night: Mainly VFR, with local MVFR possible. Definite
SHRA, Chance TSRA.
Sunday: VFR. Chance SHRA, Chance TSRA.
Sunday Night: Mainly VFR, with areas MVFR possible. Slight chance
SHRA.
Monday: VFR. Slight chance SHRA.
Monday Night: VFR. NO SIG WX.
Tuesday: VFR. NO SIG WX.
Tuesday Night: VFR. NO SIG WX.
Wednesday: VFR. Chance SHRA.

&&

.HYDROLOGY...
The threat for localized heavy downpours and isolated flash flooding
is possible this weekend across our region. The Weather Prediction
Center Day 2 Excessive Rainfall Outlook has northern NY in slight
risk or at least 15% chance of rainfall exceeding flash flood
guidance within 25 miles of a given point. The area of greatest
concern based on anticipated precipitation amounts would be across
the High Peaks of northern NY, with a secondary area of concern over
central VT, given recent rainfall amounts. Current forecasts
indicate between 0.60 and 1.50 inches of rainfall is expected with
localized amounts of 2.0 to 3.0 inches possible in the heavier
thunderstorm activity late Saturday into Sunday. Please continue to
monitor the latest forecast for additional details over this
upcoming weekend.

&&

.MARINE...
Unseasonably strong winds are expected on Saturday when a Lake
Wind Advisory will be needed for Lake Champlain. South winds
may exceed 25 knots by daybreak and may increase above 30 knots
on the broad lake at times during the day. Rough waves are
expected to develop in response to the strong winds. Wave
heights on the broad lake and inland sea may build into the 3 to
5 feet range briefly Saturday.

&&

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

&&

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