Marine Weather Net

Provincetown MA to Chatham MA to Nantucket MA out 20 NM Marine Forecast


TODAY

SE
WINDS
5 - 10
KNOTS

TONIGHT

W
WINDS
10 - 15
KNOTS

THU

NW
WINDS
5 - 10
KNOTS

THU NIGHT

NE
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
ANZ254 Forecast Issued: 416 AM EDT Wed Oct 28 2020

GALE WATCH IN EFFECT FROM THURSDAY EVENING THROUGH FRIDAY EVENING
Today...Se Winds 5 To 10 Kt, Becoming S 10 To 15 Kt With Gusts Up To 20 Kt This Afternoon. Seas 3 To 4 Ft. Rain Likely. Patchy Fog This Afternoon. Vsby 1 To 3 Nm, Decreasing To 1 Nm Or Less This Afternoon.
Tonight...W Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 3 To 4 Ft.
Thu...Nw Winds 5 To 10 Kt, Becoming Ne In The Afternoon. Seas 2 To 4 Ft. Patchy Fog. Rain. Vsby 1 Nm Or Less.
Thu Night...Ne Winds 15 To 20 Kt With Gusts Up To 30 Kt, Increasing To 25 To 30 Kt With Gusts Up To 40 Kt After Midnight. Seas 4 To 7 Ft. Rain. Vsby 1 Nm Or Less.
Fri...Ne Winds 25 To 30 Kt With Gusts Up To 45 Kt. Seas 9 To 12 Ft. Showers.
Fri Night...N Winds 20 To 25 Kt With Gusts Up To 35 Kt, Diminishing To 15 To 20 Kt With Gusts Up To 25 Kt After Midnight. Seas 8 To 11 Ft. A Chance Of Showers.
Sat...N Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 6 To 9 Ft.
Sat Night...Se Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 4 To 6 Ft.
Sun...S Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 4 To 6 Ft. A Chance Of Showers.
Sun Night...Sw Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 5 To 8 Ft. A Chance Of Showers. 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.
SHARE THIS PAGE:           
Area Forecast Discussion
National Weather Service Boston/Norton MA
350am EDT Wednesday Oct 28 2020

Synopsis
Weak low pressure tracking south of New England will bring a period of rain this morning before exiting this afternoon. High pressure briefly moves in tonight. The remnants of Zeta will bring a soaking windswept rain Thursday into Friday morning, with rain changing to snow late Thursday night before ending across the interior, especially in the hills. Behind this departing system, dry but blustery and cold weather follows later Friday. High pressure returns this weekend with dry but chilly weather Saturday followed by milder temperatures Sunday and next Monday.

Near Term - Until 6pm This Evening
Low amplitude shortwave in progressive pattern will result in a fast moving surface wave which tracks south of New Eng this morning. Deep moisture and modest forcing for ascent will bring a period of rain this morning to much of SNE but focused across the coastal plain. Given the quick movement of this system, expect rain to exit the CT valley by late morning, ending in RI and eastern MA between noon and 2 pm. Rainfall will average 0.10-0.25" with locally higher amounts south of the Mass Pike. Plenty of low level moisture lingers behind the system so low clouds will persist through the afternoon, although some breaks of sun are possible late in the day in the CT valley. Chilly morning with temps in the 40s with rain, with highs recovering into the 50s south of the Mass Pike in the afternoon.

Short Term - 6pm This Evening Through 6pm Thursday
Tonight... Mid level confluent flow with surface ridging will result in dry conditions tonight. Moisture from Zeta should remain to the south through tonight. Low clouds will erode this evening, but mid/high clouds will be overspreading the region during the night leading to mostly cloudy skies. Lows range from the upper 30s in interior northern and western MA to mid 40s near the south coast.

Thursday... Low pressure assocd with remnants of Zeta will move NE to mid Atlantic by Thu evening, while deep moisture plume lifts north across SNE. Soundings shows some drier air in the low levels which may delay onset of the rainfall so we opted to slow down timing of the rain more in line with the ECMWF. Rain should be overspreading the south coast in the morning but likely holding off until mid afternoon north of the Mass Pike. Highs will be mostly 45-50 with low/mid 50s possible along the south coast and Cape/Islands, but falling temps later in the afternoon as cooler low level temps begin to drain southward.

Long Term - Thursday Night Through Tuesday
Highlights... * Soaking rain Thu night/Fri from remnants of Zeta, likely ending as wet snow inland, especially in the hills.

* Blustery/cold Fri and Sat, then milder Sunday

* Rain chances return Sunday, drying out Monday and Tuesday

Details... All eyes remain on a wet and blustery period late Thursday into Friday as a couple of disturbances bring widespread rain, gusty winds, and even snow to southern New England. The two systems in question are, first, the remnants of Hurricane Zeta which should make landfall in the Gulf of Mexico Wednesday night before lifting into the mid-Atlantic within 24 hours; second is a mid-latitude upper level disturbance that tracks eastward, just behind the post tropical system.

This series of systems will provide a good soaking to the drought stricken area thanks in part to a generous tap of tropical moisture (PWATs (Precipitable Waters) 1 to 3 standard deviations above normal for late October) beneath the right rear quadrant of a sprawling 165 kt 300 mb jet. This will provide plenty of forcing for ascent, together with the strong low level jet. All indications are that we could see a good 1 to 2 inches of rain before all is said and done late Friday.

The biggest question concerns precipitation type, namely when/where rain switches over to snow as winds begin to pull in subfreezing air through the column. Ensemble guidance continues to indicate a good chance of a switch over to snow during the overnight hours Thursday into early Friday...the best chance of accumulation being in the high terrain of the Berkshires and Worcester Hills. This remains a low confidence forecast when it comes to snow amounts given that we remain 48 hours out...there are still some significant questions. Exact timing will make a big difference as snow will of course stand a better chance of accumulating during the overnight hours. After quite a warm stretch the ground will struggle to accumulate snow, but lack of solar insolation and intensity can help to overcome that. This system is on the weaker end, remaining an open wave at 700 mb (weaker than the ECMWF (European Centre for Medium-Range Weather Forecasts) was showing yesterday). However, with strong dynamic forcing and frontogenesis we could see our first few inches of snow. A much colder airmass arrives behind the system Friday, and as this cold air filters in there's a decent chance we'll see snowflakes closer to the coast. Still, would not expect any accumulation.

This system will also bring some strong winds with it. A very strong low level jet develops which will bring gusty winds on Friday, especially for our marine zones. A Gale Watch is in effect, and seas of 10 to 14 ft will be possible on the outer waters. Northeast winds on Friday may lead to some minor coastal flooding on the northeast/east facing shores, but very low astronomical tides will help keep coastal flooding from being a bigger issue.

A much colder airmass overhead will lead to likely our coldest night of the season so far on Friday night, down into the 20s (teens in the highest elevations). Should see some improvement by Saturday night but still quite cold, at the freezing mark or below away from the coast. This is thanks to high pressure which also keeps things dry for the first half of the weekend. Sunday unsettled weather returns ahead of a mid level trough. Southerly flow, though, will help to moderate temperatures. By next week things turn dry and cooler.

Marine
Today...Southerly winds becoming SW/W during the afternoon over south coastal waters. Gusts to 20 kt developing in the afternoon. Seas below SCA. Vsbys reduced to 1-3 miles in rain and fog, improving from west to east during the afternoon.

Tonight...W/NW winds with gusts to 20 kt at times. Good vsbys.

Thursday...Light N/NW winds turning NE and increasing in the afternoon. Gusts to 25 kt over south coastal waters by late in the day. Vsbys lowering to 1-3 miles in developing rain and fog.

Outlook /Thursday Night through Sunday/... Thursday Night: Moderate risk for gale force winds with gusts up to 40 kt. Areas of rough seas. Rain showers. Local visibility 1 to 3 nm.

Friday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 12 ft. Chance of rain showers.
Friday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 12 ft.

Saturday: Winds less than 25 kt. Areas of rough seas.
Saturday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.
Sunday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Chance of rain showers.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None. MARINE...Gale Watch from Thursday evening through Friday evening for ANZ231>235-237-254>256. Gale Watch from late Thursday night through Friday evening for ANZ250-251.