189
FXUS61 KBOX 052349
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
749 PM EDT Sat Sep 5 2026

.WHAT HAS CHANGED...
Issued a coastal flood advisory for tonight`s high tide for the
Cape and Islands, and could need to be extended into the Sunday
evening high tide.

&&

.KEY MESSAGES...

- Mostly cloudy with periods of off-and-on light showers tonight
  into early Sunday, before trending mostly sunny by Sunday
  afternoon. High risk for rip currents along the eastern coast
  Sunday, with minor coastal flooding around the evening high
  tide tonight and Sunday night for the Cape and Islands.

- Dry conditions Labor Day through much of Wednesday. Pattern
  becomes more unsettled Wednesday night into late-week with
  periods of showers possible and gusty winds possible Thursday.

&&

.DISCUSSION...
KEY MESSAGE 1...Mostly cloudy with periods of off-and-on light
showers tonight into early Sunday, before trending mostly sunny by
Sunday afternoon. High risk for rip currents along the eastern
coast, with minor coastal flooding around the evening high tide
tonight and Sunday night for the Cape and Islands.

Slow-moving, closed mid/upper low pressure over the Canada
Maritimes is helping to send wrap- around moisture in northeast
flow across much of New England, within a broad cyclonic mid-
level flow. This is leading to mostly cloudy skies this
afternoon with scattered hit-or- mostly-miss light showers, with
northeast winds around 10 mph. Expect these conditions to
generally hold steady through the afternoon, with the best shot
at light showers being in interior Southern New England. However
later tonight and overnight, a compact but pretty robust
shortwave evident in afternoon water vapor imagery well north of
Montreal digs south- southeastward through New England,
supporting at least a continuation of mostly cloudy conditions,
but also support a risk for showers spreading back eastward
overnight into early Sunday. By mid to late Sunday morning,
subsidence in the wake of this disturbance brings decreased
cloud cover with more sunshine and lighter northerly winds into
Sunday afternoon. Any showers this afternoon into early Sunday
won`t amount to much in terms of impacts, but there will be some
showers to dodge at times.

Northerly to northeast flow this weekend combined with rising
astronomical tides support a risk for very minor coastal
flooding around the evening high tides tonight and again on
Sunday night for the Cape and Islands. A coastal flood advisory
has been issued for tonight`s high tide, and another advisory or
coastal flood statement could be needed again for Sunday
night`s high tide. Overall minor impacts anticipated to the
typically more vulnerable spots (Easy Street on Nantucket and
Sesuit Harbor in Dennis). There is also an high risk for rip
currents along east-facing shorelines in eastern MA, as offshore
seas rise to around 4-6 ft overnight into Sunday.

Cloudy conditions and northeast breezes will help offset modest
cool advection tonight, leading to lows in the mid to upper
50s. Highs Sunday top out in the upper 60s near the eastern
coastline with the onshore flow, but should reach into the low
to mid 70s under increasing sunshine by afternoon elsewhere.

KEY MESSAGE 2...Dry conditions Labor Day through much of
Wednesday. Pattern becomes more unsettled Wednesday night into
late-week with periods of showers possible and gusty winds
possible Thursday.

The deeper mid-level trough shifts further eastward through the
day Monday while higher heights advect in as a mid-level ridge
builds to the west. This will bring in warmer temperatures aloft
with 925mb temperatures +15-17C. NW flow and a sufficiently
mixed boundary layer accompanied mainly clear skies should help
yield high temperatures in the the mid to upper 70s for most.
High pressure will support mainly dry conditions Monday with
similar conditions and temperatures likely for Tuesday under the
same pattern.

Ensemble guidance shows a signal for a transition to a more
unsettled pattern mid to late week. Flow aloft becomes more
zonal with a few embedded shortwave troughs moving through late
Wednesday through late-week. This should be accompanied by a
plume of above normal moisture (120-150% of normal) and a jet
positioned to supply lift across the region. This should be
enough to support periods of showers later Wednesday/Wednesday
night into Friday. There is spread across guidance in the finer
details of the timing of the waves which will influence timing
of the showers. Overall, there isn`t a strong signal for flash
flooding at this time. Marginal instability in place may owe to
a storm or downpour depending on the timing.

Another thing we will need to monitor is the potential for a
period of gusty winds Thursday. An 850mb 35-45kt LLJ positions
across southern New England into Thursday. If winds mix down
efficiently, this would support gusty winds. There is a signal
for anomalously gusty winds on the ECMWF EFI (still fairly far
out). Flow looks to become more westerly behind the passage of
the first wave with a signal for CAA. Both things that could
facilitate the mixing down of the higher winds aloft (to some
extent at least). As mentioned, timing of these waves are lower
confidence and this could have influence on when we get the
better mixing and thus the gusty winds. So plenty of details to
be worked out. If things align, ensembles show potential for
gusts in the 30-40 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 cooler airmass pushes
in sometime later Thursday into Friday with cooler temperatures
arriving by Friday (upper 60s/low 70s).

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

00z TAF Update:

Tonight: Moderate confidence.

Mainly BKN VFR/MVFR ceilings with periodic light -SHRA. A
disturbance aloft moves ESE from Quebec bringing a more uniform
batch of showers from N to S between 06Z and 15Z. NE winds
around 5-10 kt.

Sunday: High confidence.

BKN VFR/MVFR ceilings early Sunday, with any MVFR ceilings
improving to VFR mid to late-morning. NE winds 5-10 kt early
shift to NNE by late morning/early afternoon at 6-12 kts.
Cape/Islands terminals may see occasional gusts up to 20 kts.
BOS may hold onto NE/ENE winds after clouds clear.

Sunday Night: High Confidence.

VFR. NW winds 5-10 kts.

KBOS Terminal...High confidence in TAF. Batch of -SHRA possible
overnight. Most likely between 08-13Z. Brief MVFR cigs possible
in that similar timeframe.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday Night through Thursday/...

Labor Day through Tuesday Night: VFR.

Wednesday: VFR. Breezy.

Wednesday Night: VFR. Windy with gusts up to 30 kt. Chance
SHRA.

Thursday: VFR. Windy with local gusts up to 30 kt.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Sunday Night: High confidence.

SCAs remain in effect for the eastern outer waters late tonight
through Sunday as seas build to around 4-6 ft. NE gusts around
15-20 kt tonight into early Sunday, before becoming northerly
the rest of Sunday around 10-15 kt. Off-and-on light showers
this afternoon, but a better shot for showers exists overnight
to early Sunday; but only minor reductions to visibility, at
worst to 4 miles, are expected.

Outlook /Sunday Night through Thursday/...

Labor Day: Winds less than 25 kt. Areas of seas approaching
5 ft.

Monday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Tuesday through Tuesday Night: Winds less than 25 kt.

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 30 kt. Seas locally approaching 5 ft.

Wednesday Night: Low risk for gale force winds with gusts up to
35 kt. Areas of rough seas. Chance of rain showers.

Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Areas of rough seas.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents from 2 AM EDT Sunday through Sunday
     evening for MAZ007-014>016-019-022>024.
RI...None.
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Sunday for ANZ250-
     254-255.

&&

$$

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