Storm Watch 4, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
155 AM EDT Wed Sep 23 2026

.WHAT HAS CHANGED...

Storm Watches have been put up over the waters for Friday and
Saturday.

&&

.KEY MESSAGES...

- Dry, cool, and breezy weather continues through Thursday.

- A strong coastal low pressure system will bring impacts to
southern New England in the form of rain, rough seas, strong winds,
and coastal flooding/erosion Friday into the weekend. Exact timing
and magnitude of the winds and rain remain unknown.

&&

.DISCUSSION...

KEY MESSAGE 1...Dry, cool, and breezy weather continues through
Thursday.

More of the same over the next 48 hours as a sprawling high pressure
continues to sit over eastern Canada maintaining cooler than average
northeast flow over southern New England. High temperatures each day
at expected to remain in the low 60s (east coast, closer to the
onshore wind) to upper 60s (CT Valley). Normal highs for late
September are 5-10 degrees warmer. As the pressure gradient tightens
ahead of the approaching storms we'll continue to see those winds
ramping up, gusting 25 to 35 mph both Wednesday and Thursday.

KEY MESSAGE 2...A strong coastal low pressure system will bring
impacts to southern New England in the form of rain, rough seas,
strong winds, and coastal flooding/erosion Friday into the weekend.
Exact timing and magnitude of the winds and rain remain unknown.

Models continue to be consistent in indicating potential for a
strong low pressure system to make its way up the eastern seaboard
and eventually into the Northeast by Friday. Once here, detached
from strong steering flow, the low becomes entrenched overhead, even
retrograding back to the west for a time. This spells a prolonged
period of wet and windy weather Friday through Sunday, though exact
placement and magnitude of impacts remains uncertain. The latest
ensemble probabilities continue to indicate the greatest rainfall
potential (2+") over eastern MA and RI. The strongest winds will be
over the waters where Storm Watches have been hoisted starting on
Friday. On land the strongest winds will be along the coast and in
the higher elevations. Wind headlines will likely be needed as
ensemble guidance indicates >50% chance of gusts over 40 mph, even a
20-30% chance of gusts nearing 60 mph over Cape Cod and the islands.
Specific impacts will come into focus as we learn the eventual track
of the low. Timing of this early season nor'easter while trees still
have all of their leaves will lead to a greater concern for wind
damage to trees than if this were to happen late in the fall season.

Minor coastal flooding and significant coastal erosion is also a
concern as we experience a prolonged period of gusty NE winds,
combined with high astronomical tides. The greatest risk will be for
eastern facing beaches, as early as the Friday afternoon's high tide
for Nantucket, and as early as the Friday night high tide in Boston
Harbor. Many locations will see several tide cycles of minor
flooding well into the weekend. The low center lingers, weakening,
Sunday before finally exiting east around Monday.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

06Z update...

Through 12Z...High confidence.

NE winds of 5 to 15 kt tonight with 20-25 kt gusts at times
across the southeast New England coast and 25-30 kt for
Nantucket.

Wednesday and Wednesday Night...High confidence.

Mainly VFR. NE winds of 10 to 20 kt with gusts of 20 to 30 kt,
strongest towards the southeast New England coast. Gusts near 35
kt for Nantucket.

Thursday...High confidence.

VFR, outside of MVFR cigs over ACK. NE winds of 10 to 20 kt with
gusts of 20 to 30 kt, strongest towards the southeast New
England coast. Gusts near 35 kt for Nantucket.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR. Strong winds with local gusts up to 40 kt.

Friday: VFR. Strong winds with gusts up to 45 kt. Chance SHRA.

Friday Night: VFR. Strong winds with gusts up to 40 kt. Chance
SHRA.

Saturday: VFR. Strong winds with gusts up to 40 kt. Chance
SHRA, slight chance TSRA.

Saturday Night: Mainly VFR, with local MVFR possible. Strong
winds with local gusts up to 40 kt. Chance SHRA, slight chance
TSRA.

Sunday: Mainly VFR, with areas MVFR possible. Windy with gusts
up to 35 kt. Chance SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Thursday...High Confidence.

NE winds 20-30 kt with gusts up to 35 kt at times Wednesday and
Thursday as strong 1030+ mb high pressure over southeast
Ontario moves eastward into Quebec. This northeast fetch will
yield rough seas on the ocean waters, 6-12 ft. Dry weather and
good visibility prevail.

Outlook /Thursday Night through Sunday/...

Thursday Night: Moderate risk for gale force winds with local
gusts up to 45 kt. Rough seas up to 17 ft. Chance of rain
showers.

Friday: gale force winds with gusts up to 45 kt. Rough seas up
to 20 ft. Chance of rain showers.

Friday Night: gale force winds with gusts up to 45 kt. Rough
seas up to 22 ft. Chance of rain showers, slight chance of
thunderstorms.

Saturday: gale force winds with gusts up to 45 kt. Rough seas
up to 21 ft. Rain showers likely, chance of thunderstorms.

Saturday Night: Strong winds with local gusts up to 45 kt.
Rough seas up to 19 ft. Rain showers likely, slight chance of
thunderstorms.

Sunday: Strong winds with gusts up to 35 kt. Rough seas up to
16 ft. Rain showers likely, slight chance of thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ230-250-
     251.
     Gale Warning from 8 PM this evening to 8 PM EDT Thursday for
     ANZ231-254.
     Gale Warning from 5 AM early this morning to 8 PM EDT Thursday
     for ANZ232>235-237-281.
     Small Craft Advisory from 5 AM early this morning to 8 PM EDT
     Thursday for ANZ236.
     Gale Warning until 8 PM EDT Thursday for ANZ255-256-282-283.

&&

DISCUSSION...BW
AVIATION...BW
MARINE...BW