Cape Cod Bay Alt Marine Forecast
| Today...N Winds 5 To 10 Kt. Seas 1 Foot Or Less. Wave Detail: N 1 Foot At 3 Seconds And Se 1 Foot At 12 Seconds. |
| Tonight...Se Winds Around 5 Kt, Becoming Sw Around 5 Kt After Midnight. Seas 1 Foot Or Less. Wave Detail: N 1 Foot At 4 Seconds And Se 1 Foot At 11 Seconds. |
| Sun...S Winds Around 5 Kt, Increasing To 10 To 15 Kt With Gusts Up To 20 Kt In The Afternoon. Seas 1 Foot Or Less, Then Around 2 Ft In The Afternoon. Wave Detail: Sw 1 Foot At 2 Seconds And N 1 Foot At 4 Seconds, Becoming Ne 1 Foot At 3 Seconds And S 1 Foot At 3 Seconds. |
| Sun Night...S Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 2 To 3 Ft. Wave Detail: S 1 Foot At 2 Seconds And Ne 1 Foot At 3 Seconds. A Chance Of Showers After Midnight. |
| Mon...Se Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 2 To 3 Ft. Wave Detail: Se 2 Ft At 4 Seconds And Se 2 Ft At 10 Seconds. Showers Likely. |
| Mon Night...Ne Winds Around 10 Kt. Gusts Up To 20 Kt In The Evening. Seas Around 2 Ft. Wave Detail: Se 2 Ft At 9 Seconds And E 1 Foot At 4 Seconds. A Chance Of Showers In The Evening. |
| Tue Through Wed Night...S Winds 5 To 10 Kt. Seas Around 2 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. |
| Area Forecast Discussion National Weather Service Boston/Norton MA 254am EDT Sat August 15 2026 .WHAT HAS CHANGED... No significant changes to the forecast. .KEY MESSAGES... - Very comfortable temperatures this weekend with mainly dry conditions. There is a moderate risk for rip currents as well this weekend. - Rain returns late Sunday into Monday, followed by quieter weather through most of next week. - Seasonably warm temperatures and moderate humidity return through the middle of next week, followed by increasing shower chances late in the week. KEY MESSAGE 1...Very comfortable temperatures this weekend with mainly dry conditions. Clear skies and light winds early this morning are supporting effective radiational cooling. Lows fall into the 50s across the cooler outlying locations, while urban centers remain near 60 degrees by sunrise. Given these conditions, areas of valley fog have begun to develop and can be seen on satellite imagery using the Nighttime Microphysics RGB, with fog gradually filling the valleys. Any morning fog will erode with daytime heating and lift by mid- morning. Quiet weather is the theme for the weekend as high pressure originating from northern Canada settles across the Northeast through the first half of Sunday. However, there remains a very low chance for an isolated shower from mid to late afternoon, mainly across eastern Massachusetts, as a potent mid-level shortwave with an associated cold pool(a region of relatively cold air) of -18C brushes the eastern fringes of the region. Given PWATs (Precipitable Waters) are quite low, between 0.6 and 0.8 inches, and a notably dry airmass remains in place, the threat for a stray shower is very low. Our thinking is that this robust shortwave will result in more cloud cover than anything else across eastern areas. Temperatures remain seasonable, with highs generally ranging from the upper 70s to lower 80s. Another cool night is expected Saturday night, with clear skies and light winds supporting effective radiational cooling. Lows fall into the lower to middle 50s across the cooler outlying locations, while urban centers remain near 60 degrees. Despite the pleasant weather, a moderate risk for rip currents is expected today and Sunday. Those heading to the beach should remain aware of local conditions and check with lifeguards or beach staff regarding rip current risks at their specific location. High pressure begins to shift offshore Sunday as a low pressure system approaches from the Great Lakes. Increasing warm air advection will bring increasing clouds through the afternoon, while temperatures remain seasonable in the upper 70s and lower 80s. Humidity will gradually increase as dew points rise into the lower 60s. Most, if not all, of the daylight hours remain dry, with the next opportunity for rainfall arriving Sunday night into Monday. KEY MESSAGE 2...Rain returns late Sunday into Monday, followed by quieter weather through most of next week. Confidence remains high that most, if not all, of the daylight hours Sunday remain dry. Rainfall arrives late Sunday, with the steadiest rain anticipated overnight through early Monday. We are now entering the time range where high-resolution guidance can begin to better resolve this period. While some guidance brings rain into western Massachusetts and western Connecticut as early as late afternoon, prior to sunset, ensemble guidance supports a later arrival, with measurable rainfall generally arriving between 8pm and midnight. There is increasing certainty in the overall evolution of this system, with one area of low pressure likely passing across northern New England and a secondary low tracking south of New England across the Mid-Atlantic. This evolution is also supported by the ECMWF (European Centre for Medium-Range Weather Forecasts) EFI and Shift of Tails for Quantitative Precipitation Forecast, which highlight both of these regions. With southern New England positioned between these two areas, confidence in the highest rainfall totals occurring across the region has diminished, lowering the threat for widespread flash flooding. However, PWATs (Precipitable Waters) increase to between 1.8 and 2.1 inches overnight into Monday, supporting the potential for locally heavier downpours. A Marginal Risk for Excessive Rainfall (level 1 of 4) remains in place for much of New England Sunday night into Monday, primarily due to the potential for localized flash flooding. Ensemble guidance currently supports a general range of 0.25 to 0.50 inches across southern New England, though localized higher amounts are possible, especially beneath heavier downpours. Given the expected cloud cover and showers, Monday will be cooler, with highs generally ranging from the mid-70s to around 80 degrees. It will also be fairly humid, with dew points remaining elevated and resulting in rather sticky conditions. KEY MESSAGE 3...Seasonably warm temperatures and moderate humidity return through the middle of next week, followed by increasing shower chances late in the week. Drier air advects in from the northwest beginning Monday night into Tuesday, leading to another dry stretch Tuesday through Wednesday, and possibly into the first half of Thursday, as surface high pressure builds back into the region. Temperatures remain seasonable, with highs in the lower to middle 80s and tolerable humidity as dew points remain in the lower to middle 60s. Ensemble guidance continues to signal a transition toward more unsettled weather late in the week, with shower chances returning and temperatures potentially trending slightly below normal. Marine Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Through Sunday...High confidence. Tranquil boating conditions are expected as high pressure traverses the Northeast through the weekend. Unsettled conditions arrive late Sunday into Monday with the passage of a low pressure system. Winds from the north today become somewhat variable as surface high pressure moves overhead. Nearshore sea breezes develop, with winds generally 10 to 15 kt. On Sunday, winds shift to the south and increase to less than 20 kt. Sunday night into Monday, seas build to 4-6 ft with wind gusts up to 25 kt. These are marginal conditions for a Small Craft Advisory, but one may need to be considered for Sunday night into Monday. Outlook /Sunday Night through Wednesday/... Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas locally approaching 5 ft. Chance of rain showers. Monday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Rain showers likely. Monday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Tuesday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Wednesday: Winds less than 25 kt. NOAA Boston MA Office: Watches - Warnings - Advisories CT...None. MA...None. RI...None. Marine None. |
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