865
FXUS61 KBOX 061938
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
338 PM EDT Sun Sep 6 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- Mix of clouds and sun with off-and-on showers through the
  afternoon, with decreasing clouds and a cool evening tonight.
  Full sun, seasonable temperatures and low humidity for the
  Labor Day Monday holiday.

- Dry conditions Tuesday through much of Wednesday. Pattern
  becomes more unsettled later Wednesday into early Friday with
  periods of showers possible.

&&

.DISCUSSION...
KEY MESSAGE 1...Mix of clouds and sun with off-and-on showers
through the afternoon, with decreasing clouds and a cool evening
tonight. Full sun, seasonable temperatures and low humidity for
the Labor Day Monday holiday.

We`re still governed by broad cyclonic flow aloft around a closed
mid/upper low over Nova Scotia, a feature which has moved very
little over the last 24 hours. This has led to a mix of clouds and
sun, and some heating where clouds have scattered has led to
"destructive sunshine" which has blossomed additional cloudiness
with scattered pop-up showers moving southward. These clouds and
scattered showers will continue through sundown. An additional
shortwave and mid-level moisture move southward from coastal ME
could sustain cloud cover across eastern New England for a few hours
after sundown, but we should trend mostly clear with falling
dewpoints overnight supporting good radiational cooling. There could
be some patchy mist or fog developing around sunrise, especially in
those areas which received rain. We also have one final evening with
nuisance splashover around the early-evening high tide at Nantucket
and the Cape and Islands with coastal flood advisories still in
effect. We fell just short of Advisory criterion last night at
Nantucket at 4.91 ft, and tonight should end up being similar
with a higher high-tide but weaker northerly winds. Lows tonight
should dip into the mid to upper 40s in the favored radiational
cooling locations, and in the low to mid 50s elsewhere, warmest
lows Cape and Islands.

Rising 500 mb heights on Labor Day Monday support full sun and
temperatures warming back into the mid to upper 70s, with low
humidity levels (dewpoints in the 40s to low 50s!) with some
northwesterly winds around 10 mph. Overall about as ideal weather
conditions for outdoor activities as one could ask for. By Monday
evening, clear skies early favoring strong radiational cooling then
give way to increasing midlevel cloud cover from the northwest by
the pre-dawn hours as a strong shortwave disturbance aloft passes to
our northeast. Lows end up slightly warmer, in the to mid 50s for
most, with mid/upper 50s for the eastern and southern coastlines.

KEY MESSAGE 2...Dry conditions Tuesday through much of
Wednesday. Pattern becomes more unsettled later Wednesday into
early Friday with periods of showers possible.

On Tuesday, the deeper mid-level trough continues to shift further
eastward as a mid-level ridge continues to build in from the west.
925mb temperatures warm to +17-18C yielding high temperatures in the
upper 70s with locations potentially hitting the 80 degree mark in
the valleys. High pressure in place will support mainly dry
conditions.

Ensemble guidance shows a signal for a transition to a more
unsettled pattern mid to late week. The mid-level ridge begins to
break down Wednesday, becoming more zonal by Thursday. Ensemble
guidance shows a consensus with a series of shortwave troughs moving
through the flow later Wednesday through Friday. This should be
accompanied by a plume of above normal moisture, rising to 160-190%
of normal by early Thursday yielding PWATS of 1.5" approaching 2.0".
The positioning of an upper jet should supply ascent for periods of
showers. There is spread across guidance in the finer details of the
timing of the waves which will influence timing of the showers. A
shortwave pushes through sometime Wednesday evening/night triggering
the first round of showers which should taper off through the
morning Thursday (at latest). The next wave moves through late
Thursday/Thursday Night bringing another round of showers. With the
timing of the waves still variable across guidance this leaves some
uncertainty in thunderstorm/downpour potential. There will be plenty
of moisture to support downpours; however, the timing of the wave
would need be early enough to tap into the marginal instability
build through the day for convection. Something to keep monitoring.
For now, we are not seeing a strong signal for severe or flash
flooding, just periods of showers with generally light accumulations
(< 0.60").

An 850mb 35-45kt LLJ shifts across southern New England into
Thursday. There does raise a flag for potentially gustier winds;
however, this will come down to how well we can mix down from 850mb
or even 925mb. If things align, ensembles show potential for gusts
in the 20-35 mph range on Thursday across the land and coastal
waters. Still plenty of details to work out in the pattern before we
come into better agreement about the gusts, but something to watch
for now.

Temperatures Wednesday/Thursday lean near to slightly above normal
with temperatures in the mid to upper 70s. A cold front pushes
through early Friday bringing a cooler airmass this will support
highs in the upper 60s low 70s.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

15z TAF Update:

Today: High confidence.

SCT-BKN VFR/MVFR ceilings (020-040 bases) continue as of mid-
morning, with widely SCT light -SHRA around pushing southward.
While showers come to an end shortly, anticipate some lifting
of cloud bases closer to VFR levels by afternoon. Another surge
of moisture comes down now over central Maine could bring an
increase in clouds toward BKN later this afternoon for eastern
terminals. North to northeast winds around 5-10 kt.

Tonight: High confidence.

Mostly VFR as cloud cover decreases. Some risk for patchy fog in
the river valleys prior to sunrise (08-12z) but its development
is uncertain. Winds decrease to light northerly.

Monday and Monday Night: High confidence.

VFR. NW winds increase to around 8-12 kt during the daytime,
easing and becoming WNW with an increase in VFR clouds after
06z Tue.

KBOS Terminal...High confidence in TAF. Mix of SCT-BKN VFR/MVFR
ceilings, but should trend VFR by early afternoon. NE winds
around 5-10 kt. Seabreeze possible but could be late in the
day.

KBDL Terminal...High confidence in TAF.

Outlook /Monday Night through Friday/...

Tuesday through Tuesday Night: VFR.

Wednesday: VFR. Breezy.

Wednesday Night: Mainly VFR, with local IFR possible. Windy
with local gusts up to 30 kt. Chance SHRA.

Thursday: VFR. Windy with areas of gusts up to 30 kt. Slight
chance SHRA.

Thursday Night: VFR. Breezy. Slight chance SHRA.

Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Through Monday Night: High confidence.

SCAs continue through early this evening to allow for residual 5
ft seas to subside.

Northerly winds around 15-20 kt this afternoon decrease to
around 10-15 kt overnight tonight. Essentially a repeat of those
wind conditions for Monday. Northerly winds pick back up again
Monday to around 15-20 kt, then subside overnight. Seas will
continue to decrease to 3 ft or less all waters by tonight and
remain in that range through Monday night.

Off-and-on light showers will continue through late this
afternoon. Otherwise dry weather with good visibility then
predominates.

Outlook /Monday Night through Friday/...

Tuesday through Wednesday: Winds less than 25 kt.

Wednesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas. Chance of rain
showers.

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 9 ft. Slight chance of rain
showers.

Thursday Night: Winds less than 25 kt. Areas of rough seas.
Chance of rain showers.

Friday: Winds less than 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ007-
     014>016-019-022>024.
     Coastal Flood Advisory until 8 PM EDT this evening for
     MAZ022>024.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ250-
     254-255.

&&

$$

DISCUSSION...Loconto/Mensch
AVIATION...Loconto/Mensch
MARINE...Loconto/Mensch