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National Weather Service Marine Forecast FZUS51 KBOX

FZUS51 KBOX 180507
CWFBOX

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

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

ANZ200-181800
107 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.

ANZ250-181800
Coastal waters east of Ipswich Bay and the Stellwagen Bank National Marine Sanctuary
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

REST OF TONIGHT
W winds 20 to 25 kt with gusts up to 30 kt. Seas 6 to 9 ft. Wave Detail: SE 7 ft at 11 seconds and NW 6 ft at 5 seconds.

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

WED NIGHT
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 S 2 ft at 3 seconds.

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

FRI NIGHT
SW winds 10 to 15 kt. Gusts up to 20 kt after midnight. Seas 3 to 5 ft. Wave Detail: SE 3 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. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 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.

ANZ251-181800
Massachusetts Bay and Ipswich Bay
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

REST OF TONIGHT
W winds 20 to 25 kt with gusts up to 30 kt. Seas 3 to 5 ft. Wave Detail: NW 4 ft at 4 seconds and E 4 ft at 12 seconds.

WED
W winds 15 to 20 kt with gusts up to 25 kt, becoming NW 5 to 10 kt in the afternoon. Seas 3 to 5 ft. Wave Detail: NW 4 ft at 4 seconds and E 4 ft at 12 seconds.

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

FRI NIGHT
SW winds around 10 kt, becoming W after midnight. Seas 2 to 4 ft. Wave Detail: S 2 ft at 3 seconds and E 2 ft at 8 seconds.

SAT THROUGH SUN
SW winds 15 to 20 kt. Seas 3 to 4 ft. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt with gusts up to 25 kt. Seas around 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.

ANZ231-181800
Cape Cod Bay
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

REST OF TONIGHT
W winds 15 to 20 kt with gusts up to 25 kt. Seas 2 to 4 ft. Wave Detail: SE 4 ft at 11 seconds and NW 3 ft at 5 seconds.

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

WED NIGHT
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 NW 1 foot at 4 seconds.

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

SAT THROUGH SUN
SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 3 ft. Wave Detail: SW 3 ft at 3 seconds and E 2 ft at 9 seconds. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt with gusts up 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.

ANZ254-181800
Coastal waters from Provincetown MA to Chatham MA to Nantucket MA out 20 nm
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

REST OF TONIGHT
NW winds 15 to 20 kt with gusts up to 30 kt. Seas 7 to 10 ft. Wave Detail: SE 9 ft at 11 seconds and NW 5 ft at 5 seconds.

WED
NW winds 15 to 20 kt with gusts up to 25 kt, diminishing to 5 to 10 kt in the afternoon. Seas 5 to 8 ft. Wave Detail: SE 7 ft at 11 seconds and NW 4 ft at 6 seconds.

WED NIGHT
SE winds around 5 kt. Seas 4 to 6 ft. Wave Detail: SE 5 ft at 10 seconds and N 2 ft at 6 seconds.

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

THU NIGHT THROUGH FRI NIGHT
SW winds 5 to 10 kt. Seas 3 to 5 ft. Wave Detail: SE 4 ft at 9 seconds and NW 1 foot at 3 seconds.

SAT THROUGH SUN
SW winds 15 to 20 kt with gusts up to 25 kt. Seas 4 to 6 ft. Wave Detail: S 5 ft at 5 seconds and E 4 ft at 9 seconds. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt with gusts up to 25 kt. Seas 4 to 6 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.

ANZ255-181800
Coastal Waters extending out to 25 nm South of Marthas Vineyard and Nantucket
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

REST OF TONIGHT
NW winds 15 to 20 kt with gusts up to 25 kt. Seas 7 to 10 ft. Wave Detail: S 10 ft at 11 seconds and NW 2 ft at 5 seconds.

WED
NW winds 15 to 20 kt, diminishing to 5 to 10 kt in the afternoon. Seas 5 to 8 ft, subsiding to 4 to 6 ft in the afternoon. Wave Detail: S 8 ft at 10 seconds and NW 1 foot at 5 seconds, becoming S 6 ft at 10 seconds and NW 1 foot at 4 seconds.

WED NIGHT
SE winds around 5 kt. Seas 3 to 5 ft. Wave Detail: S 5 ft at 10 seconds.

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

THU NIGHT
SE winds 5 to 10 kt. Seas 2 to 4 ft. Wave Detail: SE 4 ft at 9 seconds.

FRI AND FRI NIGHT
SW winds 5 to 10 kt. Seas 2 to 4 ft. Wave Detail: SE 3 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. A chance of rain.

SUN NIGHT
SW winds 20 to 25 kt. Seas 4 to 6 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.

ANZ256-181800
Coastal Waters from Montauk NY to Marthas Vineyard extending out to 20 nm South of Block Island
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THURSDAY MORNING

REST OF TONIGHT
NW winds 15 to 20 kt. Seas 7 to 10 ft. Wave Detail: S 9 ft at 11 seconds and NW 3 ft at 5 seconds.

WED
NW winds 10 to 15 kt, becoming NE 5 to 10 kt in the afternoon. Seas 5 to 8 ft, subsiding to 5 to 6 ft in the afternoon. Wave Detail: S 8 ft at 10 seconds and NW 1 foot at 4 seconds, becoming S 6 ft at 10 seconds.

WED NIGHT
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 5 ft at 9 seconds.

THU NIGHT THROUGH FRI NIGHT
SW winds 5 to 10 kt. Seas 3 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: SW 5 ft at 5 seconds and SE 3 ft at 9 seconds. A chance of rain.

SUN NIGHT
SW winds 20 to 25 kt. Seas 4 to 5 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.

ANZ232-181800
Nantucket Sound
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

REST OF TONIGHT
NW winds 15 to 20 kt with gusts up to 25 kt. Seas 4 to 6 ft. Wave Detail: W 3 ft at 4 seconds and SE 3 ft at 11 seconds.

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

WED NIGHT
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 NW 1 foot at 3 seconds.

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

SAT THROUGH SUN NIGHT
W winds 15 to 20 kt. Seas 2 to 3 ft. Wave Detail: SW 3 ft at 5 seconds and E 2 ft at 9 seconds. 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.

ANZ233-181800
Vineyard Sound
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

REST OF TONIGHT
NW winds 15 to 20 kt with gusts up to 25 kt. Seas 4 to 6 ft. Wave Detail: S 5 ft at 11 seconds and NW 2 ft at 5 seconds.

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

WED NIGHT
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 and S 1 foot at 2 seconds.

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

SAT THROUGH SUN
SW winds 15 to 20 kt. Seas 2 to 3 ft. Wave Detail: SW 3 ft at 5 seconds and SE 1 foot at 8 seconds. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt. Seas 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.

ANZ234-181800
Buzzards Bay
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT UNTIL 8 AM EDT THIS MORNING

REST OF TONIGHT
NW winds 15 to 20 kt with gusts up to 25 kt. Seas 3 to 5 ft. Wave Detail: S 3 ft at 11 seconds and NW 2 ft at 5 seconds.

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

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

SAT THROUGH SUN
SW winds 15 to 20 kt. Seas 2 to 3 ft. Wave Detail: SW 3 ft at 5 seconds and SE 2 ft at 9 seconds. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt. Seas 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.

ANZ235-181800
Rhode Island Sound
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THIS EVENING

REST OF TONIGHT
NW winds 15 to 20 kt. Seas 5 to 8 ft. Wave Detail: S 8 ft at 11 seconds and NW 2 ft at 5 seconds.

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

WED NIGHT
S winds 5 to 10 kt. Seas 3 to 4 ft. Wave Detail: S 4 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 THROUGH FRI NIGHT
SW winds 5 to 10 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. Seas 2 to 4 ft. Wave Detail: SW 4 ft at 5 seconds and SE 3 ft at 9 seconds. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt with gusts up to 25 kt. Seas 3 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.

ANZ237-181800
Block Island Sound
107 AM EDT Wed Mar 18 2026

SMALL CRAFT ADVISORY IN EFFECT THROUGH THIS EVENING

REST OF TONIGHT
NW winds 10 to 15 kt with gusts up to 20 kt. Seas 5 to 8 ft. Wave Detail: S 7 ft at 11 seconds and W 2 ft at 4 seconds.

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

WED NIGHT
S winds 5 to 10 kt. Seas 3 to 4 ft. Wave Detail: SE 4 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 THROUGH FRI NIGHT
SW winds 5 to 10 kt. Seas 2 to 4 ft. Wave Detail: SE 4 ft at 9 seconds and SW 1 foot at 4 seconds.

SAT THROUGH SUN
SW winds 10 to 15 kt with gusts up to 20 kt. Seas 2 to 4 ft. Wave Detail: SW 4 ft at 5 seconds and SE 3 ft at 9 seconds. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt. Seas 3 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.

ANZ230-181800
Boston Harbor
107 AM EDT Wed Mar 18 2026

REST OF TONIGHT
W winds 15 to 20 kt with gusts up to 25 kt. Waves around 2 ft.

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

WED NIGHT
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 THROUGH FRI NIGHT
W winds 10 to 15 kt. Waves around 2 ft.

SAT THROUGH SUN
SW winds 15 to 20 kt. Waves 2 to 3 ft. A chance of rain.

SUN NIGHT
W winds 15 to 20 kt. Waves around 2 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.

ANZ236-181800
Narragansett Bay
107 AM EDT Wed Mar 18 2026

REST OF TONIGHT
NW winds 10 to 15 kt with gusts up to 20 kt. Waves 2 to 3 ft, except 4 to 6 ft at the bay entrance.

WED
NW winds 5 to 10 kt, becoming S in the afternoon. Waves 2 to 3 ft.

WED NIGHT
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 THROUGH FRI NIGHT
W winds 5 to 10 kt. Waves around 2 ft.

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

SUN NIGHT
W winds 10 to 15 kt with gusts up to 20 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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