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National Weather Service Marine Forecast FZUS51 KBOX

FZUS51 KBOX 181105
CWFBOX

Coastal Waters Forecast for Massachusetts and Rhode Island
National Weather Service Boston/Norton MA
704 AM EDT Wed Mar 18 2026

Coastal waters from the Merrimack River MA to Watch Hill RI out to 25 NM

ANZ200-190000
704 AM EDT Wed Mar 18 2026

Synopsis for Massachusetts and Rhode Island coastal waters

High pres builds over the waters Wed into Thu, moving offshore Fri as a cold front approaches from the west. Low pressure passes the region this weekend.

ANZ250-190000
Coastal waters east of Ipswich Bay and the Stellwagen Bank National Marine Sanctuary
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

TODAY
NW winds 15 to 20 kt with gusts up to 25 kt, becoming W 5 to 10 kt this afternoon. Seas 5 to 7 ft. Wave Detail: SE 6 ft at 11 seconds and NW 5 ft at 5 seconds.

TONIGHT
S winds 5 to 10 kt. Seas 3 to 5 ft. Wave Detail: SE 5 ft at 10 seconds and NW 2 ft at 4 seconds.

THU
S winds 5 to 10 kt, becoming SE 10 to 15 kt in the afternoon. Seas 3 to 4 ft. Wave Detail: SE 4 ft at 10 seconds and SE 2 ft at 3 seconds.

THU NIGHT
S winds 10 to 15 kt, becoming SW after midnight. Seas 2 to 4 ft. Wave Detail: SE 3 ft at 9 seconds and SE 2 ft at 3 seconds.

FRI
SW winds 10 to 15 kt. Seas 2 to 4 ft. Wave Detail: SE 3 ft at 8 seconds and SW 2 ft at 3 seconds.

FRI NIGHT
S winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 4 ft. Wave Detail: E 4 ft at 9 seconds and SW 2 ft at 3 seconds. A chance of rain after midnight.

SAT THROUGH SUN NIGHT
NW winds 20 to 25 kt with gusts up to 30 kt. Seas 3 to 5 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ251-190000
Massachusetts Bay and Ipswich Bay
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

TODAY
W winds 15 to 20 kt with gusts up to 25 kt, becoming NW 5 to 10 kt this afternoon. Seas 3 to 5 ft. Wave Detail: NW 4 ft at 4 seconds and E 4 ft at 11 seconds.

TONIGHT
S winds 10 to 15 kt, diminishing to 5 to 10 kt after midnight. Seas 2 to 3 ft. Wave Detail: E 3 ft at 10 seconds and NW 2 ft at 4 seconds.

THU
S winds 5 to 10 kt, becoming SE 10 to 15 kt in the afternoon. Seas 2 to 3 ft. Wave Detail: E 3 ft at 10 seconds and SE 2 ft at 3 seconds.

THU NIGHT
S winds 10 to 15 kt, becoming SW after midnight. Seas 2 to 3 ft. Wave Detail: E 3 ft at 9 seconds and SE 2 ft at 4 seconds.

FRI
SW winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: SE 3 ft at 9 seconds and S 1 foot at 3 seconds.

FRI NIGHT
S winds 10 to 15 kt. Seas 2 to 3 ft. Wave Detail: E 3 ft at 9 seconds and S 2 ft at 3 seconds. A chance of rain after midnight.

SAT THROUGH SUN
W winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 4 ft. A chance of rain.

SUN NIGHT
NW winds 20 to 25 kt. Seas 3 to 5 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ231-190000
Cape Cod Bay
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

TODAY
NW winds 10 to 15 kt with gusts up to 20 kt, becoming N 5 to 10 kt this afternoon. Seas 2 to 4 ft. Wave Detail: NW 3 ft at 5 seconds and SE 3 ft at 11 seconds.

TONIGHT
S winds around 5 kt. Seas 2 to 3 ft. Wave Detail: NW 2 ft at 5 seconds and E 2 ft at 8 seconds.

THU
SE winds 5 to 10 kt. Seas around 2 ft. Wave Detail: E 2 ft at 7 seconds and N 1 foot at 4 seconds.

THU NIGHT
S winds 5 to 10 kt. Seas around 2 ft. Wave Detail: SE 2 ft at 8 seconds and SE 1 foot at 2 seconds.

FRI
SW winds 5 to 10 kt. Seas around 2 ft. Wave Detail: SE 2 ft at 6 seconds and SW 1 foot at 2 seconds.

FRI NIGHT
SW winds around 10 kt. Seas around 2 ft. Wave Detail: E 2 ft at 9 seconds and SW 1 foot at 2 seconds. A chance of rain after midnight.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 4 ft. A chance of rain.

SAT NIGHT
SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 3 ft.

SUN AND SUN NIGHT
SW winds around 15 kt, becoming NW 20 to 25 kt. Seas 2 to 4 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ254-190000
Coastal waters from Provincetown MA to Chatham MA to Nantucket MA out 20 nm
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

TODAY
NW winds 15 to 20 kt with gusts up to 25 kt, diminishing to 5 to 10 kt this afternoon. Seas 6 to 9 ft, subsiding to 5 to 7 ft this afternoon. Wave Detail: SE 7 ft at 11 seconds and NW 4 ft at 6 seconds, becoming SE 6 ft at 10 seconds and NW 3 ft at 6 seconds.

TONIGHT
SE winds around 5 kt. Seas 4 to 6 ft. Wave Detail: SE 5 ft at 10 seconds and NW 2 ft at 6 seconds.

THU
SE winds 5 to 10 kt. Seas 3 to 5 ft. Wave Detail: SE 5 ft at 9 seconds and N 1 foot at 5 seconds.

THU NIGHT
SE winds 5 to 10 kt, becoming SW after midnight. Seas 3 to 4 ft. Wave Detail: SE 4 ft at 9 seconds and N 1 foot at 3 seconds.

FRI AND FRI NIGHT
S winds 10 to 15 kt. Seas 2 to 4 ft. Wave Detail: SE 4 ft at 9 seconds and SW 2 ft at 3 seconds.

SAT THROUGH SUN
SW winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 ft. Wave Detail: S 4 ft at 5 seconds and E 4 ft at 9 seconds. A chance of rain.

SUN NIGHT
NW winds 20 to 25 kt with gusts up to 30 kt. Seas 4 to 6 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ255-190000
Coastal Waters extending out to 25 nm South of Marthas Vineyard and Nantucket
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

TODAY
NW winds 15 to 20 kt, diminishing to 5 to 10 kt this afternoon. Seas 5 to 8 ft. Wave Detail: S 8 ft at 10 seconds and W 3 ft at 5 seconds.

TONIGHT
SE winds around 5 kt. Seas 4 to 6 ft. Wave Detail: S 5 ft at 10 seconds and W 1 foot at 6 seconds.

THU
E winds 5 to 10 kt. Seas 3 to 4 ft. Wave Detail: SE 4 ft at 9 seconds.

THU NIGHT
SE winds around 5 kt, becoming S after midnight. Seas 2 to 4 ft. Wave Detail: SE 3 ft at 9 seconds.

FRI AND FRI NIGHT
S winds 10 to 15 kt. Seas 2 to 4 ft. Wave Detail: SE 4 ft at 9 seconds and SW 3 ft at 4 seconds.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 ft. Wave Detail: S 5 ft at 5 seconds and E 4 ft at 9 seconds. A chance of rain.

SAT NIGHT
SW winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 ft.

SUN AND SUN NIGHT
SW winds 15 to 20 kt, becoming NW 25 to 30 kt. Seas 3 to 5 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ256-190000
Coastal Waters from Montauk NY to Marthas Vineyard extending out to 20 nm South of Block Island
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

TODAY
NW winds 10 to 15 kt with gusts up to 20 kt, becoming NE 5 to 10 kt this afternoon. Seas 6 to 8 ft, subsiding to 5 to 6 ft this afternoon. Wave Detail: S 8 ft at 10 seconds and W 2 ft at 5 seconds, becoming S 6 ft at 10 seconds and W 1 foot at 5 seconds.

TONIGHT
S winds around 5 kt. Seas 4 to 5 ft. Wave Detail: S 5 ft at 10 seconds.

THU
SE winds 5 to 10 kt. Seas 4 to 5 ft. Wave Detail: SE 4 ft at 9 seconds.

THU NIGHT
S winds around 5 kt. Seas 3 to 4 ft. Wave Detail: SE 4 ft at 9 seconds.

FRI
SW winds 5 to 10 kt. Seas 3 to 4 ft. Wave Detail: SE 3 ft at 9 seconds.

FRI NIGHT
SW winds 10 to 15 kt. Gusts up to 20 kt after midnight. Seas 3 to 4 ft. Wave Detail: SW 3 ft at 4 seconds and SE 3 ft at 9 seconds. A chance of rain after midnight.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 ft. A chance of rain.

SAT NIGHT
SW winds 15 to 20 kt with gusts up to 25 kt. Seas 4 to 5 ft.

SUN AND SUN NIGHT
SW winds 15 to 20 kt, becoming NW 20 to 25 kt. Gusts up to 30 kt. Seas 3 to 5 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ232-190000
Nantucket Sound
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

TODAY
NW winds 10 to 15 kt with gusts up to 20 kt, becoming N 5 to 10 kt this afternoon. Seas 3 to 5 ft. Wave Detail: W 3 ft at 4 seconds and SE 2 ft at 11 seconds.

TONIGHT
S winds around 5 kt. Seas 2 to 3 ft. Wave Detail: SE 2 ft at 10 seconds and NW 1 foot at 4 seconds.

THU
SE winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: SE 2 ft at 9 seconds and W 1 foot at 3 seconds.

THU NIGHT
S winds around 5 kt. Seas around 2 ft. Wave Detail: SE 1 foot at 2 seconds and SE 1 foot at 9 seconds.

FRI AND FRI NIGHT
S winds 10 to 15 kt. Seas around 2 ft. Wave Detail: SW 2 ft at 3 seconds and E 2 ft at 9 seconds.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 3 ft. Wave Detail: S 3 ft at 4 seconds and E 2 ft at 9 seconds. A chance of rain.

SAT NIGHT
SW winds around 15 kt with gusts up to 20 kt. Seas 2 to 4 ft.

SUN AND SUN NIGHT
SW winds around 15 kt, becoming NW 20 to 25 kt. Seas 2 to 4 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ233-190000
Vineyard Sound
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

TODAY
NW winds 10 to 15 kt with gusts up to 20 kt, becoming SW 5 to 10 kt this afternoon. Seas 3 to 5 ft. Wave Detail: S 4 ft at 10 seconds and NW 2 ft at 5 seconds.

TONIGHT
S winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: S 3 ft at 9 seconds and SW 1 foot at 4 seconds.

THU
SE winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: S 2 ft at 9 seconds.

THU NIGHT
S winds 5 to 10 kt, becoming SW after midnight. Seas around 2 ft. Wave Detail: SE 2 ft at 8 seconds and SE 1 foot at 2 seconds.

FRI
SW winds 5 to 10 kt, increasing to 10 to 15 kt in the afternoon. Seas around 2 ft. Wave Detail: SE 2 ft at 8 seconds and SW 1 foot at 3 seconds.

FRI NIGHT
SW winds 10 to 15 kt. Seas around 2 ft. Wave Detail: SW 2 ft at 4 seconds and SE 1 foot at 8 seconds. A chance of rain after midnight.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 4 ft. A chance of rain.

SAT NIGHT
SW winds 15 to 20 kt. Seas 2 to 4 ft.

SUN AND SUN NIGHT
SW winds 15 to 20 kt, becoming NW 20 to 25 kt. Seas 2 to 3 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ234-190000
Buzzards Bay
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

TODAY
NW winds 10 to 15 kt with gusts up to 20 kt, becoming SW 5 to 10 kt this afternoon. Seas 2 to 4 ft. Wave Detail: S 3 ft at 10 seconds and NW 2 ft at 5 seconds.

TONIGHT
S winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: S 2 ft at 9 seconds and S 1 foot at 4 seconds.

THU
SE winds 5 to 10 kt. Seas around 2 ft. Wave Detail: S 2 ft at 9 seconds.

THU NIGHT
S winds 5 to 10 kt. Seas around 2 ft. Wave Detail: S 2 ft at 8 seconds and SE 1 foot at 2 seconds.

FRI
SW winds 5 to 10 kt, increasing to 10 to 15 kt in the afternoon. Seas around 2 ft. Wave Detail: SW 1 foot at 2 seconds and SE 1 foot at 8 seconds.

FRI NIGHT
SW winds 10 to 15 kt. Seas around 2 ft. Wave Detail: SW 2 ft at 3 seconds and SE 1 foot at 8 seconds. A chance of rain after midnight.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 4 ft. A chance of rain.

SAT NIGHT
SW winds 15 to 20 kt. Seas 2 to 3 ft.

SUN AND SUN NIGHT
SW winds 10 to 15 kt, becoming NW 20 to 25 kt. Seas 2 to 3 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ235-190000
Rhode Island Sound
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THIS EVENING

TODAY
NW winds 10 to 15 kt with gusts up to 20 kt, becoming SW 5 to 10 kt this afternoon. Seas 5 to 7 ft, subsiding to 3 to 5 ft this afternoon. Wave Detail: S 7 ft at 10 seconds and W 2 ft at 5 seconds, becoming S 5 ft at 10 seconds and W 1 foot at 5 seconds.

TONIGHT
S winds 5 to 10 kt. Seas 3 to 5 ft. Wave Detail: S 5 ft at 10 seconds.

THU
SE winds 5 to 10 kt. Seas 3 to 4 ft. Wave Detail: S 4 ft at 9 seconds.

THU NIGHT
S winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: SE 3 ft at 9 seconds.

FRI
SW winds 5 to 10 kt, increasing to 10 to 15 kt in the afternoon. Seas 2 to 3 ft. Wave Detail: SE 3 ft at 8 seconds and SW 2 ft at 3 seconds.

FRI NIGHT
SW winds 10 to 15 kt. Seas 2 to 3 ft. Wave Detail: S 3 ft at 4 seconds and SE 3 ft at 9 seconds. A chance of rain after midnight.

SAT
S winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 4 ft. A chance of rain.

SAT NIGHT
SW winds 15 to 20 kt. Seas 3 to 5 ft.

SUN
SW winds 15 to 20 kt. Seas 2 to 3 ft. A chance of rain.

SUN NIGHT
NW winds 20 to 25 kt. Seas 2 to 4 ft. A chance of rain and snow.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ237-190000
Block Island Sound
704 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THIS EVENING

TODAY
NW winds 5 to 10 kt, becoming SW this afternoon. Seas 4 to 6 ft. Wave Detail: S 6 ft at 11 seconds and W 2 ft at 4 seconds.

TONIGHT
S winds 5 to 10 kt. Seas 3 to 5 ft. Wave Detail: S 5 ft at 10 seconds.

THU
SE winds 5 to 10 kt. Seas 3 to 4 ft. Wave Detail: SE 4 ft at 9 seconds.

THU NIGHT
S winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: SE 3 ft at 9 seconds.

FRI
SW winds 5 to 10 kt. Seas 2 to 3 ft. Wave Detail: SE 3 ft at 9 seconds.

FRI NIGHT
SW winds 10 to 15 kt. Seas 2 to 3 ft. Wave Detail: SE 3 ft at 8 seconds and SW 2 ft at 3 seconds. A chance of rain after midnight.

SAT
S winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 4 ft. A chance of rain.

SAT NIGHT
SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 4 ft.

SUN
SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 3 ft. A chance of rain.

SUN NIGHT
NW winds 20 to 25 kt. Seas 2 to 4 ft. A chance of rain and snow.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ230-190000
Boston Harbor
704 AM EDT Wed Mar 18 2026

TODAY
W winds 10 to 15 kt with gusts up to 20 kt, becoming NW 5 to 10 kt this afternoon. Waves around 2 ft this morning, then 1 foot or less.

TONIGHT
S winds 10 to 15 kt, diminishing to 5 to 10 kt after midnight. Waves 1 foot or less.

THU
SE winds 5 to 10 kt. Waves 1 foot or less.

THU NIGHT
S winds 10 to 15 kt, becoming SW 5 to 10 kt after midnight. Waves around 2 ft in the evening, then 1 foot or less.

FRI
SW winds 5 to 10 kt. Waves 1 foot or less.

FRI NIGHT
S winds 10 to 15 kt. Waves 1 foot or less, then around 2 ft after midnight. A chance of rain after midnight.

SAT THROUGH SUN NIGHT
NW winds 20 to 25 kt. Waves around 2 ft. A chance of rain.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

ANZ236-190000
Narragansett Bay
704 AM EDT Wed Mar 18 2026

TODAY
NW winds 5 to 10 kt, becoming S this afternoon. Waves 2 to 3 ft.

TONIGHT
S winds 5 to 10 kt, diminishing to around 5 kt after midnight. Waves 2 to 3 ft.

THU
SE winds around 5 kt, increasing to 5 to 10 kt in the afternoon. Waves 2 to 3 ft.

THU NIGHT
S winds 5 to 10 kt. Waves around 2 ft.

FRI
SW winds 5 to 10 kt. Waves around 2 ft.

FRI NIGHT
SW winds around 10 kt. Waves around 2 ft. A chance of rain after midnight.

SAT
S winds 10 to 15 kt with gusts up to 20 kt. Waves 2 to 3 ft. A chance of rain.

SAT NIGHT
SW winds 10 to 15 kt with gusts up to 20 kt. Waves 2 to 3 ft.

SUN
SW winds 10 to 15 kt with gusts up to 20 kt. Waves around 2 ft. A chance of rain.

SUN NIGHT
NW winds 15 to 20 kt with gusts up to 25 kt. Waves 2 to 3 ft. A chance of rain and snow.

Seas are reported as significant wave height, which is the average of the highest third of the waves. Individual wave heights may be more than twice the significant wave height.

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