957
FXUS61 KBTV 280747
AFDBTV

Area Forecast Discussion
National Weather Service Burlington VT
347 AM EDT Fri Jun 28 2024

.SYNOPSIS...
A beautiful day is on tap with plenty of sunshine and mild
temperatures in the upper 60s to mid 70s. Clouds increase tonight
with occasional showers developing on Saturday, along with breezy
south to southwest wind gusts of 30 to 45 mph. Localized heavy
downpours are possible on Saturday afternoon into Sunday, which will
need to be watched closely for the potential for localized flooding.
Drier weather returns by the start of next week.

&&

.NEAR TERM /THROUGH SATURDAY NIGHT/...
As of 342 AM EDT Friday...A chilly morning acrs our cwa with SLK
down to 36F as of 3:45 AM and BTV at 50F which is the coldest
for the date since 1990.

The near term concerns wl be gusty winds and developing precip
on Saturday acrs our fa. Today is very quiet with 1022mb high
pres shifting from the northern NY into the Gulf of Maine by 00z
this evening. Plenty of sunshine expected with comfortable
temps in the upper 60s to mid 70s. Light and variable winds
become south by this evening at 4 to 8 mph.

Tonight-Saturday...As sfc high pres shifts to our east, deep
south/southwest flow develops ahead of our next s/w trof with strong
moisture advection. Pw values surge to near 2.0" by 00z Sunday,
which are near daily maximum for the date or 2 to 4 std above normal
for late June. The dynamics associated with approaching
mid/upper lvl trof and orientation of the jet stream aloft wl
help us to maximize qpf amounts, but intially instability is
limited so rainfall rates should be held in check. Helping to
advect this deep layer moisture into our region with be an
anomalously strong 850mb jet of 50 to 60 knots from the
southwest on Sat. Sounding profiles show a sharp inversion
around 2.5kft, with top of the mixed layer winds of 35 to 42
knots on Sat. We should see enhanced southerly flow given
inversion height, especially acrs the central/northern CPV with
localized gusts 40 to 45 mph likely midday Saturday. Also,
secondary enhanced area of gusty winds are likely over the
northern Dacks along the route 11 corridor from near Malone to
Altona, where gusts to 40 mph is likely. A few isolated power
outages are possible in these areas on Saturday.

Timing of rain showers on Saturday acrs our cwa is rather
challenging, especially in the morning into early aftn hours.
Initially airmass is rather dry at all levels and expect some virga
associated with first surge of warm air/moisture advection. However,
secondary s/w energy and another surge of moisture advection
develops btwn 18-21z from sw to ne acrs our region and expect
showers to increase in areal coverage, with developing widespread
wetting rainfall likely acrs most of the region by 21z Saturday. I
have tried to integrate this thinking into the pop grids for Sat. As
we have mentioned multiple times over the past several days, many
ingredients are coming together for localized heavy downpours on Sat
aftn/evening, including warm cloud depths of 12.0 to 13.0 kft, pw
values near 2.0", sw orientation of 850mb jet of 50 to 60 knots, and
rrq of 250mb jet passing to our north acrs central Canada. Given the
orientation of the llvl jet toward the High Peaks, this area wl need
to be watched closely for localized heavy rainfall and potential
flooding, especially overnight as instability aloft increases to
help enhance localized heavier rainfall rates. WPC has upgraded
parts of northern NY in their latest day 2 ERO to slight risk, which
from our perspective looks reasonable given the synoptic scale
setup. Difficult to pin point exact qpf amounts thru 00z Sunday, but
generally 0.25 to 0.75 with highest values over northern NY with a
tenth of an inch or less over eastern/southern VT. Have placed
localized heavy rain wording into the grids btwn 21-00z acrs
northern NY on Sat, as elevated instability increases btwn 150-400
J/kg from west to east. Also, given the increasing elevated
instability parameters off both the NAM 3KM and HRRR have mention
isolated thunder. SPC has expanded their day 2 marginal risk to
cover all of northern NY, but feel the greatest threat maybe aft
00z, when instability increases further. Highs on Sat in the upper
60s to mid 70s, with increasing humidity toward sunset.

&&

.SHORT TERM /SUNDAY/...
As of 244 PM EDT Thursday...A 50 knot southwesterly low-level jet
will move directly overhead Saturday afternoon into Saturday
evening, as our area is squeezed between high pressure to our east
and a low lifting to our north. With the resultant warm air
advection on southwesterly winds, a temperature inversion will
develop in the 850 to 950 mb layer, which will prevent the strongest
momentum air from mixing to the surface in lower elevations.
Nonetheless, expect a gusty day with south/southwest wind gusts 20
to 30 mph for most locations. Higher elevations (above 2500 ft) will
gust higher, potentially 45+ mph. The Champlain Valley will also see
stronger winds in the 25 to 35 mph range as flow is channeled
up the valley. Peak wind gusts will be observed Saturday
afternoon/early evening just before the onset of rain. Once
steady rain moves into the area, winds will diminish slightly as
the rain stabilizes the air. Latest thinking on the timing for
arrival of steadier precipitation will be Saturday afternoon for
northern NY, and late afternoon/early evening for VT. However,
some earlier scattered showers are possible before the arrival
of the steady precipitation. Given the low-level inversion,
instability will be marginal if any, and thus have kept mention
of thunderstorms out of the forecast for Saturday. However,
ingredients are favorable for some heavy rainfall overnight.
Precipitable water values climb to around 2.0 inches, which is
around 200% climatological normal. In addition, deep warm cloud
depths of over 12 kft will increase precipitation rates, though
lack of instability will temper heavy rainfall potential. At
this point, it appears system will be just progressive enough to
preclude any widespread training threat, though some isolated
areas may have multiple heavy rain showers move overhead and
thus may see some ponding of water in poor drainage areas.
Current Excessive Rainfall Outlook from WPC for Saturday has our
forecast area outlined in the Marginal Risk. Will be watching
things closely, but not expecting widespread issues at this
point. Storm total amounts for Saturday through Saturday night
will be in the 0.5 to 1.0 inch range.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 244 PM EDT Thursday...Steady rain will come to an end Sunday
morning, but showers will continue thanks to a series of fronts that
will move through during the day. As the fronts/troughs move
through, will see decreasing moisture and thus potential for any
moderate to heavy rain within showers will be lessening. However,
steepening low and mid-level lapse rates will result in some
marginal instability, though depth of moisture and instability will
be relatively shallow. Thinking we will see a few embedded
thunderstorms during the day within the rain showers, though limited
instability will temper severe potential.

Once the final cold front sweeps through late Sunday, will be in for
a drier start to the work week as expansive high pressure builds in
from the west. Highs in the 70s/low 80s with dewpoints generally in
the 50s will feel quite refreshing and should be a beautiful stretch
of weather overall. A gradual warming trend can be expected going
into midweek. The next chance for showers will be in the
Wednesday/Thursday timeframe.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Through 06z Saturday...VFR conditions expected at all taf sites
for the next 12 to 24 hours as sfc high pres is building
directly overhead. Given the 1 degree spread at SLK and crnt
temp at cross over value, expect some periods of fog and
associated IFR vis is possible btwn 07-11z. Feel the potential
is in the 30-40% range, so have utilized a tempo group to
highlight the potential, otherwise light and variable winds will
become south 4 to 8 knots toward 00z this evening.

Outlook...

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

&&

.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 be be above 30 knots on
the broad lake at times during the day. Rough waves could
develop quickly. 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...Taber
NEAR TERM...Taber
SHORT TERM...Duell
LONG TERM...Duell
AVIATION...Taber
HYDROLOGY...Taber
MARINE...Kutikoff