Marine Weather Net

Montauk NY to Marthas Vineyard out 20 NM South of Block Island Marine Forecast




15 - 20


15 - 20



The Marine Weather Forecast In Detail:
ANZ256 Forecast Issued: 427 AM EDT Thu Sep 23 2021

Today...Se Winds Around 15 Kt With Gusts Up To 25 Kt. Seas 4 To 6 Ft. A Chance Of Showers This Morning.
Tonight...Se Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 5 To 6 Ft. A Chance Of Showers.
Fri...Se Winds 15 To 20 Kt, Becoming S 10 To 15 Kt In The Afternoon. Gusts Up To 25 Kt. Seas 5 To 6 Ft. Patchy Fog. Showers Likely.
Fri Night...Sw Winds Around 10 Kt, Becoming W After Midnight. Seas 4 To 6 Ft. Patchy Fog. Showers Likely. Vsby 1 To 3 Nm.
Sat And Sat Night...W Winds 5 To 10 Kt. Seas 4 To 5 Ft.
Sun Through Mon Night...W Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 4 To 6 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
418am EDT Thu September 23 2021

Our area remains in between high pressure to our east, and a slow-moving cold front to our west. For southern New England, this will result in considerable cloudiness and scattered showers. This slow-moving front will bring showers and thunderstorms into western sections late Thursday night, moving eastward across the region during Friday. Showers and thunderstorms then linger over eastern Massachusetts Saturday, otherwise improving weather. More showers possible Sunday and Tuesday. No big warm ups or cool downs are expected.

Near Term - Until 6pm This Evening
Not much change to the overall synoptic pattern today. High pressure over the North Atlantic, and a low pressure over the Great Lakes. As a result, not expecting much change in the forecast outcome. Still looking at a bunch of clouds and scattered showers at times. Light rainfall amounts. Another day of above normal temperatures.

Short Term - 6pm This Evening Through 6pm Friday
A cold front to our west will continue to approach our region tonight into Friday. This front will take quite some time to make its way through southern New England. Thinking this front will still be somewhere over eastern MA and RI late Friday. The main impact will be to provide a focus for stronger showers. Instability is modest, but sufficient to support a few thunderstorms. There is a chance for some stronger than garden- variety thunderstorms, provided there is sufficient shear to maximize the instability present. Still quite a few moving parts, so not yet ready to etch this in stone.

Will also need to monitor rainfall amounts. At this time, thinking we have had sufficiently light rainfall the past few days we could handle a couple of additional inches, as long as it did not fall all at once.

Generally above normal temperatures continue.

Long Term - Friday Night Through Wednesday
Highlights... * Drier, less humid air moves in over the weekend into early next week

* Mostly dry on Saturday but a series of disturbances brings periods of unsettled weather through the weekend and into next week

Details... Friday night and Saturday... As the parent low lifts into the Hudson Bay its cold front is slow to traverse southern New England, likely only as far east as central MA by Friday evening. It will make its way through by Saturday morning keeping rain in the forecast for eastern MA/RI through at least sunrise Saturday. While instability wanes after sunset enough lingers to support some scattered thunderstorms during the overnight hours.

Saturday much drier and less humid air arrives for much of the region, especially western/central parts of southern New England. However, there is some question as to weather the front stalls around eastern MA which would keep the higher dewpoints and scattered showers around during the day on Saturday. For now keeping a slight chance to a chance of showers in the forecast for eastern MA into Rhode Island with dry weather elsewhere. While the ECMWF (European Centre for Medium-Range Weather Forecasts) continues to be more bullish/wet for Saturday, both the EPS and GEFS ensemble guidance is showing a >50 percent chance of some rain through the day on Saturday. Otherwise expect a good deal of sun in western/Central MA and CT where the column is quite dry save for some moisture at 850 mb allowing for some diurnal clouds.

Sunday... The latter half of the weekend we'll see another shortwave dip down over New England with a -20C cold pool(a region of relatively cold air) at 500 mb. This will allow for more clouds and some instability driven showers. 850 mb temps cool a bit from Saturday meaning highs a bit cooler, in the low to mid 70s.

Monday through Wednesday... For the first half of the week, broad troughing remains over the eastern U.S. with periodic shortwaves rotating through the flow and bringing bouts of rain to the region. While it is difficult to time out the individual shortwaves at this time another period of showers appears likely Tuesday-Wednesday. Temperatures will trend cooler, with highs in the upper 60s and low 70s.

Forecaster Confidence Levels.

Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent.

Southeast winds continue across the waters. Seas continue to build across the southern coastal waters. Small Craft Advisories continue. May need to look at expanding advisories to more nearshore waters. Just not confident in seeing wind gusts up to 25 kt long enough across those waters.

Patchy showers/drizzle and fog possible across the waters during this period. Reduced visibility possible in the fog, but not quite as much within precipitation. Thunderstorms more possible across the coastal waters late tonight into Friday.

Outlook /Friday Night through Monday/... Friday Night through Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Sunday: Winds less than 25 kt. Seas up to 5 ft.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.
Monday: Winds less than 25 kt. Seas up to 5 ft.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.

Small Craft Advisory from 5pm this afternoon to 6pm EDT Friday for ANZ233. Small Craft Advisory from 5pm this afternoon to 2am EDT Friday for ANZ234-236. Small Craft Advisory from 7am this morning to 6pm EDT Friday for ANZ237. Small Craft Advisory from 7am this morning to 8pm EDT Friday for ANZ235. Small Craft Advisory from 8am to 8pm EDT Friday for ANZ250. Small Craft Advisory from 5pm this afternoon to 8pm EDT Friday for ANZ254. Small Craft Advisory until 8pm EDT Friday for ANZ255. Small Craft Advisory until 8pm EDT Friday for ANZ256.