Marine Weather Net

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


TONIGHT

NW
WINDS
30 - 40
KNOTS

SUN

W
WINDS
20 - 25
KNOTS

SUN NIGHT

NW
WINDS
15 - 20
KNOTS

MON

W
WINDS
10 - 15
KNOTS

The Marine Weather Forecast In Detail:
ANZ255 Forecast Issued: 716 PM EST Sat Dec 05 2020

STORM WARNING IN EFFECT UNTIL 3 AM EST SUNDAY
Tonight...Nw Winds 30 To 40 Kt With Gusts Up To 55 Kt, Diminishing To 25 To 30 Kt With Gusts Up To 45 Kt After Midnight. Seas 8 To 13 Ft. Rain Likely This Evening With Vsby 1 To 3 Nm.
Sun...W Winds 20 To 25 Kt. Gusts Up To 40 Kt, Decreasing To 30 Kt In The Afternoon. Seas 6 To 9 Ft.
Sun Night...Nw Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 4 To 7 Ft.
Mon...W Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Morning. Seas 4 To 6 Ft.
Mon Night Through Tue Night...Nw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 5 Ft.
Wed...Nw Winds Around 10 Kt. Seas 3 To 5 Ft.
Wed Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 5 Ft. A Chance Of Showers.
Thu And Thu Night...Nw Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 4 To 7 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
716pm EST Sat Dec 5 2020

Synopsis
A rapidly intensifying storm system off Cape Cod will produce gusty winds, heavy rain, and a period of accumulating heavy, wet snow. The wind and precipitation will taper off tonight. The storm exits through the Maritimes overnight. Dry and colder weather moves in for Sunday through Tuesday with a moderating trend for the middle of next week.

Near Term - Until 6am Sunday Morning
7 PM

We're in the thick of it this evening with heavy wet snow continuing as winds continue to ramp up. The low is centered directly east of MA offshore this evening with winds now having come out of the northwest. Hearing many reports of extremely wet flakes coming down across eastern MA which makes sense given the extremely mild airmass. Surface temperatures across the region generally 32-35 where we're seeing snow. Intensity has backed off since this afternoon given the best frontogenesis now lifted into northern New England. While the back edge of the precipitation is now approaching central MA, what earlier seemed like a drastic drop in radar returns toward northern MA can likely be attributed to erroneous radar attenuation due to the heavy wet snow. Additional accumulations will be slow and likely less than previously expected in the I-95 corridor owing to the warm temperatures and relatively high dewpoints (at or above freezing) limiting additional cooling.

Previous Discussion... Coastal low pressure near outer Cape Cod will move off through the Maritimes overnight. Rain and snow this evening will taper off from west to east tonight, ending latest along the Massachusetts North Shore during the overnight.

The rain/snow line mid afternoon extended from Boston and the North Shore through the western suburbs of Boston, the NW corner of Rhode Island, and Northeast CT. As the coastal low lifts past Nantucket and Outer Cape Cod, expect the colder air inland to move farther east and change the rain in RI and SE Mass to snow. That should be roughly 4pm to 7 PM. Heaviest amounts will remain from the Central Hills through the Merrimack Valley. No significant changes in forecast amounts from previous forecasts.

As the coastal low pulls away from the coast overnight, the precipitation will taper off from west to east, and clearing skies will move in from the west. Temps will cool to the 20s inland and 30-35 along the coast.

Short Term - 6am Sunday Morning Through Sunday Night
Still cyclonic flow on Sunday around the Maritime closed low. However there will also be drier air moving in. Cross sections of moisture show a little lingering moisture at or below 850 mb, but lots of dry air above that. While there may be some diurnal clouds, expect a partly to mostly sunny day. Mixing is forecast to reach 925-mb, with winds of 25-30 kt available for gusts. Temps at 925-mb will be -4 to -5C, so max surface temps mostly mid 30s to around 40.

Dry air lingers Sunday night with lighter west-northwest winds. With dew points 15 to 25, expect min temps close to that.

Long Term - Monday Through Saturday
Fairly quiet weather expected through the period. We are watching another potential cutoff low from the Ohio Valley to the mid Atlantic states early next week, but with lack of downstream blocking this time (i.e., no ridging over Greenland) system is likely to pass well south of New England. Did include some chance Probability of Precipitation near South Coast, Cape, and Islands but for most part expect this system to have little impact on SNE (as of right now, anyway). Upper flow turns more zonal for mid to late week which should allow for temperatures to moderate into 40s to around 50.

Marine
Tonight... Coastal low pressure passes near Nantucket this evening and east of Outer Cape Cod early tonight, then heads through the Gulf of Maine overnight. Strong shifting winds near the path of the low, with directions shifting out of the northwest during the night.

Winds gusting 50-55 kt this evening, diminishing to 35-40 kt after midnight. Storm Warning continues on most waters, with Gales on the remaining waters. Storms may be lowered to Gales late at night. Seas 10 to 15 feet on the exposed waters tonight.

Sunday...Diminishing northwest winds with gusts around 35 kt in the morning, then around 30 kt in the afternoon. Seas subside to 5-7 feet in the afternoon. Gales expected through the first half of the day.

Sunday night...Diminishing west-northwest winds at Small Craft Advisory levels the first half of the night. Seas 5 to 7 feet on the exposed waters.

Outlook /Monday through Thursday/... Monday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Monday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.
Tuesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.
Tuesday Night through Wednesday: Winds less than 25 kt. Seas up to 5 ft.

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

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

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...Winter Storm Warning until 7am EST Sunday for CTZ003-004. Winter Weather Advisory until 7pm EST this evening for CTZ002. MA...High Wind Warning until midnight EST tonight for MAZ007-019- 022>024. Winter Weather Advisory until 1am EST Sunday for MAZ016>019. Wind Advisory until midnight EST tonight for MAZ013>018-020- 021. Winter Storm Warning until 7am EST Sunday for MAZ003>007- 010>015-026. Winter Weather Advisory until 7pm EST this evening for MAZ002- 008-009. RI...High Wind Warning until midnight EST tonight for RIZ008. Winter Weather Advisory until 1am EST Sunday for RIZ002>004. Wind Advisory until midnight EST tonight for RIZ002>007. Winter Storm Warning until 7am EST Sunday for RIZ001. MARINE...Storm Warning until 3am EST Sunday for ANZ231>234-250-251- 254>256. Gale Warning until 11am EST Sunday for ANZ230-236. Storm Warning until 1am EST Sunday for ANZ235-237.