Marine Weather Net

Coastal Waters out 25 NM South of Marthas Vineyard and Nantucket Marine Forecast


THIS AFTERNOON

W
WINDS
10 - 15
KNOTS

TONIGHT

W
WINDS
10 - 15
KNOTS

WED

NW
WINDS
5 - 10
KNOTS

WED NIGHT

SW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ255 Forecast Issued: 1004 AM EDT Tue Aug 25 2026

This Afternoon...W Winds 10 To 15 Kt. Gusts Up To 20 Kt. Seas 2 To 3 Ft. Wave Detail: Sw 2 Ft At 5 Seconds And Se 1 Foot At 6 Seconds.
Tonight...W Winds 10 To 15 Kt With Gusts Up To 20 Kt, Diminishing To 5 To 10 Kt After Midnight. Seas 2 To 3 Ft. Wave Detail: Sw 3 Ft At 5 Seconds And Se 1 Foot At 6 Seconds.
Wed...Nw Winds 5 To 10 Kt, Becoming Sw In The Afternoon. Seas 2 To 3 Ft. Wave Detail: Sw 2 Ft At 5 Seconds And Se 2 Ft At 10 Seconds.
Wed Night...Sw Winds 5 To 10 Kt. Seas 2 To 3 Ft. Wave Detail: Se 3 Ft At 9 Seconds And Sw 1 Foot At 5 Seconds.
Thu...S Winds 5 To 10 Kt. Seas 2 To 3 Ft. Wave Detail: S 3 Ft At 7 Seconds And Sw 1 Foot At 3 Seconds.
Thu Night...S Winds Around 10 Kt. Seas 3 To 4 Ft. Wave Detail: Sw 3 Ft At 5 Seconds And Se 3 Ft At 9 Seconds. A Chance Of Showers After Midnight.
Fri...S Winds 5 To 10 Kt. Seas 3 To 4 Ft. A Chance Of Showers.
Fri Night Through Sat Night...Ne Winds 5 To 10 Kt. Seas 2 To 4 Ft. 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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Area Forecast Discussion
National Weather Service Boston/Norton MA
723am EDT Tuesday August 25 2026

.WHAT HAS CHANGED... Small Craft Advisory canceled.

.KEY MESSAGES... - Mainly dry and seasonable conditions, outside of a stray shower this afternoon across the western half of southern New England.

- Main risk for a round of scattered showers and a few thunderstorms will be sometime late Thu/Thu night into Fri with summerlike humidity. Mainly dry and seasonable weather favored for this weekend.

KEY MESSAGE 1...Mainly dry and seasonable conditions, outside of a stray shower this afternoon across the western half of southern New England.

Southern New England will be stuck between a couple of synoptic features, leaving our weather somewhere in the middle as well. High pressure over the OH Valley and central Appalachians should mean plenty of dry hours today with a steady west to southwest wind. However, the subsidence from this high pressure will not be absolute.

A mid level cold pool(a region of relatively cold air) over the Great Lakes and Ontario should generate some diurnal clouds heading into this afternoon, which will then diminish with sunset. The addition of a weak surface trough moving into southern New England could trigger a few showers this afternoon. Anticipating most unstable CAPE values between 500-750 J/kg this afternoon. Thus, cannot completely dismiss the idea for a thunderstorm or two. However, severe weather is not expected. The greatest risk for these showers will be across the western half of southern New England, away from the marine influence.

Dry weather is expected Wednesday.

As for temperatures, expect a seasonable week, with afternoon highs in the lower 80s and higher-terrain communities in the northern Worcester Hills and eastern Berkshires remaining in the middle to upper 70s. Nightly lows will be a touch cooler as clear skies and light winds allow for radiational cooling, with temperatures slipping back into the 50s while urban areas remain near 60 degrees. This setup may allow for another night of low stratus or fog. Confidence in how widespread it becomes remains low; however, it does not appear this round of fog will be as prevalent as last night.

KEY MESSAGE 2...Main risk for a round of scattered showers and a few thunderstorms will be sometime late Thu/Thu night into Fri with summerlike humidity. Mainly dry and seasonable weather favored for this weekend.

The next shortwave trough approaches from the west by late in the work week. Ahead of this approaching shortwave, summer-like humidity will return Thu into Fri. Timing quite uncertain this far out in the forecast. But appears there will be the potential for a round of scattered showers and a few thunderstorms sometime in the late Thu/Thu night into Fri time frame. CSU machine learning probs do indicate some low probs for severe weather/heavy rainfall potential. But that is really just climo for an approaching shortwave this time of year. So, not much more we can say at this point. Current guidance does indicate that drier/seasonable weather is favored to return for this upcoming weekend.

Marine
Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

Through Wednesday...High confidence.

Fairly quiet boating conditions through the first half of this week as high pressure develops across the Midwest before expanding toward the waters off the coast of southern New England. Gusty southwest flow develops today, with gusts around 20 kt. Conditions improve overnight into early Wednesday morning as winds shift to the northwest.

Outlook /Wednesday Night through Saturday/... Wednesday Night through Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.
Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.

Marine
None.