Coastal Waters out 25 NM South of Marthas Vineyard and Nantucket Marine Forecast
| Tonight...Se Winds Around 5 Kt. Seas 3 To 4 Ft. Wave Detail: S 4 Ft At 7 Seconds And S 2 Ft At 4 Seconds. A Slight Chance Of Showers After Midnight. |
| Wed...Sw Winds 5 To 10 Kt. Seas 3 To 4 Ft. Wave Detail: S 4 Ft At 7 Seconds And Sw 2 Ft At 4 Seconds. Patchy Fog In The Morning With Vsby 1 To 3 Nm. |
| Wed Night...Sw Winds Around 10 Kt. Seas 2 To 3 Ft. Wave Detail: S 3 Ft At 7 Seconds And W 1 Foot At 3 Seconds. Patchy Fog After Midnight With Vsby 1 To 3 Nm. |
| Thu...Sw Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Afternoon. Seas 2 To 3 Ft. Wave Detail: S 3 Ft At 6 Seconds And Nw 1 Foot At 4 Seconds. Patchy Fog In The Morning With Vsby 1 To 3 Nm. |
| Thu Night Through Fri Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 4 Ft. Wave Detail: Sw 3 Ft At 5 Seconds And E 1 Foot At 9 Seconds. |
| Sat Through Sun Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 3 Ft. Wave Detail: W 3 Ft At 5 Seconds And E 1 Foot At 9 Seconds. 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. |
| Area Forecast Discussion National Weather Service Boston/Norton MA 259pm EDT Tuesday August 4 2026 .WHAT HAS CHANGED... Confidence continues to increase for the region to see a stretch of warm and humid conditions for late week into the weekend. .KEY MESSAGES... - Weak low pressure brings some clouds and a low risk for a shower early Wednesday across Martha's Vineyard and Nantucket - Increasing heat and humidity across much of southern New England, along with daily afternoon pop-up thunderstorms from Thursday through this weekend. A widespread washout is not anticipated at this time. KEY MESSAGE 1...Weak low pressure brings some clouds and a low risk for a shower early Wednesday across Martha's Vineyard and Nantucket Overall a pretty quiet night, weather-wise, is expected for most of the region. Weak high pressure over CT and western MA will result in mostly clear skies with some patchy valley fog perhaps forming. Low temperatures will be seasonable, generally the lower 60s. The only other feature on the weather map is a very weak low pressure several hundred miles of southern New England. This will track northeast, and although it will pass south of Nantucket late tonite/early Wednesday morning, moisture around the low may be enough to produce a period of low clouds as far north as Cape Cod. Low (less than 25%) chance of a light shower is also possible across Martha's Vineyard and Nantucket between roughly 4a-8a. KEY MESSAGE 2...Increasing heat and humidity across much of southern New England, along with daily afternoon pop-up thunderstorms from Thursday through this weekend. A widespread washout is not anticipated at this time. There is increasing confidence in a prolonged period of midsummer warmth and humidity, along with daily chances for afternoon pop-up thunderstorms from Thursday through the upcoming weekend. However, a widespread washout is not anticipated. Given the abundant rainfall earlier this week, any storms capable of producing heavy downpours could lead to localized instances of flash flooding. This is reflected in the WPC Marginal Risk (Level 1 of 4) for excessive rainfall across western New England on Thursday and all of southern New England on Friday. Bermuda high pressure develops this week and remains anchored over the western Atlantic through the remainder of the forecast period. With persistent southwesterly flow, expect above-normal temperatures along with increasing humidity. While temperatures will be above climatological normals, they are not particularly unusual for early August. High temperatures from Thursday through Sunday should climb well into the upper 80s and lower 90s, while dewpoints rise into the lower to middle 70s. This combination will result in heat index values of 95 to 100 degrees. If current trends continue, Heat Advisories may be needed for portions of the region Thursday and Friday, and perhaps Saturday as well. One uncertainty is the degree of afternoon cloud cover and thunderstorm development, which could temper temperatures somewhat. This will be monitored over the coming days. Regarding thunderstorm chances, the overall synoptic pattern features the Bermuda High over the western Atlantic with a mid-level ridge extending across the Northeast. Embedded shortwave disturbances riding through the flow should provide enough lift to initiate scattered afternoon and evening thunderstorms from Thursday through Sunday. Although deep-layer shear remains weak, instability will be plentiful, with forecast CAPE values generally between 1,500 and 2,000 J/kg. As a result, storms should remain largely pulse-type and disorganized rather than organized severe convection. BUFKIT soundings depict tall, skinny CAPE profiles, suggesting efficient warm-rain processes and the potential for locally heavy rainfall. PWAT (Precipitable Water) values around 1.7 inches further support the threat of torrential downpours. In addition to localized flooding, gusty winds and frequent lightning will be the primary hazards. That said, not every community will experience thunderstorms each day. Many locations will remain dry, so there is no reason to cancel outdoor plans at this point. The details regarding storm coverage and placement will become clearer once the convection-allowing guidance comes into range over the next couple of days. Marine Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. The need for a Small Craft Advisory across the outer southern waters will come to an end by early this evening as seas slowly subside to below 5ft. Otherwise a "Bermuda High" will become firmly entrenched off the eastern sea board resulting in an extended period of SW winds. Outlook /Thursday through Sunday/... Thursday: Winds less than 25 kt. Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Friday: Winds less than 25 kt. Friday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Saturday: Winds less than 25 kt. Seas locally approaching 5 ft. Saturday Night: Winds less than 25 kt. Slight chance of rain showers. Sunday: Winds less than 25 kt. NOAA Boston MA Office: Watches - Warnings - Advisories CT...None. MA...High Risk for Rip Currents until 9pm EDT this evening for MAZ020- 023-024. RI...High Risk for Rip Currents until 9pm EDT this evening for RIZ006>008. Marine Small Craft Advisory until 8pm EDT this evening for ANZ255- 256. |
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