Marine Weather Net

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


TONIGHT

SW
WINDS
15 - 20
KNOTS

MON

N
WINDS
10 - 15
KNOTS

MON NIGHT

W
WINDS
5 - 10
KNOTS

TUE

W
WINDS
10
KNOTS

The Marine Weather Forecast In Detail:
ANZ255 Forecast Issued: 619 PM EDT Sun May 09 2021

SMALL CRAFT ADVISORY IN EFFECT THROUGH MONDAY EVENING
Tonight...Sw Winds 15 To 20 Kt, Becoming Se After Midnight. Gusts Up To 25 Kt. Seas 3 To 5 Ft. Rain. Patchy Fog After Midnight With Vsby 1 To 3 Nm.
Mon...N Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Morning. Seas 4 To 7 Ft. Patchy Fog. A Chance Of Rain. Vsby 1 To 3 Nm.
Mon Night...W Winds 5 To 10 Kt. Seas 4 To 7 Ft. Patchy Fog.
Tue...W Winds Around 10 Kt, Increasing To Around 15 Kt With Gusts Up To 25 Kt In The Afternoon. Seas 3 To 5 Ft.
Tue Night Through Wed Night...Nw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 5 Ft.
Thu Through Fri Night...Sw Winds Around 10 Kt. Seas 2 To 4 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
359pm EDT Sunday May 9 2021

Synopsis
Low pressure tracking just south of New England will bring a soaking rain tonight followed by gradually improving conditions Monday as the low pulls away. There could be a few isolated showers on Tuesday, but much of the upcoming week will be dry with moderating temperatures. Next potential shot for rain showers is late in the week into next weekend.

Near Term - Until 6am Monday Morning
Mid level shortwave over the Ohio valley will move east into New Eng overnight with attendant frontal wave tracking just south of New Eng. Typically the heaviest rainfall with these frontal waves is focused north of the low track which places SNE in the sweet spot for a soaking rainfall tonight as large scale forcing acts on deep moisture plume which moves across the region. Rain moves into the CT valley by early evening, reaching NE MA toward midnight. In addition, models are consistent with tight thermal gradient at 850 mb developing along the south coast toward 06z with nose of the low level jet impinging on the boundary. This will result in an area of enhanced low level frontogenesis and locally heavy rainfall focused south of the Mass Pike and particularly near the south coast. The system is progressive so duration of heavier rainfall will be limited. Expected rainfall 0.50-0.75" south of the Pike and 0.25- 0.50" to the north.

Short Term - 6am Monday Morning Through Monday Night
Monday... Deep moisture axis will be east of New Eng by 12z. Some lingering showers are possible over eastern New Eng early in the day before rain exits the region, otherwise mainly dry conditions for the rest of SNE. Given low level moisture in place expect lots of low clouds in the morning. Gradual improvement in the afternoon with partial sunshine developing from west to east as drier air filters into the region. Somewhat cool low level temps and cloud cover will result in a cool day with below normal temps. Highs mainly upper 50s to lower 60s. Light N winds with local sea breezes developing in the afternoon.

Monday night... Another shortwave rotating around upper low north of the Lakes swings through northern New Eng. Best chance for showers will be to the north, with a low risk for a brief shower in northern MA as the shortwave passes to the north. Otherwise partly cloudy skies with lows in the 40s, with some upper 30s in the Berkshires.

Long Term - Tuesday Through Sunday
Highlights... * Generally dry and quiet weather through the extended with moderating temperatures. Slightly cooler than normal heading into the middle of the week before trending near to above normal the rest of the week.

* Few isolated showers possible across the interior on Tuesday. Next shot for precipitation is late in the week into the weekend.

Tuesday... H5 trough/cutoff will be situated near the eastern Ontario early on Tuesday. This feature will dig into Northern New England by late Tuesday. A surface trough will swing through southern New England. This may bring a few isolated showers across the interior.

Will have H5 temperatures of -20 to -25 degrees Celsius moving in overhead. This in combination with diurnal heating and upper forcing should result in a mix of sunshine and clouds by the afternoon. So, did bump up sky cover toward the MOS guidance. May need to bump up further in future updates. On top of this did bump up precipitation chances to keep isolated showers across the interior. Most locations will stay dry given there really isn't much moisture available with PWATs (Precipitable Waters) between 0.25 to 0.4 inches. As previously stated this is around the 10th to 25th percentile per Storm Prediction Center CHH Sounding Climatology. Better shots for more widespread shower activity is across northern New England.

Temperatures moderating with 925 hPa air in the +5 to +7 degree Celsius range. Temperatures climbing into upper 50s and mid 60s, which is slightly cooler than this time of year.

Wednesday through Thursday... The H5 cutoff/trough lifts out of northern New England into Nova Scotia early on Wednesday. A ridge axis will build into the central Great Lakes from the Upper Mississippi River Valley. The ridge builds into the central/eastern Great Lakes on Thursday. A surface high will nudge in from the central Great Lakes on Wednesday and over the Mid Atlantic/eastern Great Lakes on Thursday.

Dry and quiet weather expect through this stretch. Anticipating it to be a bit breezy across southern New England on Wednesday due to the tight pressure gradient in place. Should see some 20-25 mph gusts during the afternoon.

High temperatures on Wednesday range from the upper 50s to mid 60s. Temperatures will moderate a bit more on Thursday with 925 hPa air getting to around +10 degrees Celsius. Highs will generally be in the 60s. There could be a few 70 degree readings across the Merrimack and CT River Valley.

Friday through Saturday... Still have lots of uncertainty in this timeframe. Should see a trough lifting through the region from the central Great Lakes/OH Valley. Uncertain mostly on the amplitude of the feature lifting through as the timing is in pretty good agreement this far out. Though there is a lack of consensus amongst EPS/GEFS and deterministic guidance with the surface low track associated with the trough. Have stuck with the NBM guidance given the uncertainty, which keeps slight chance to chances of rain on Friday and Saturday.

Have more confidence in the continued warmth with 925 hPa air of +8 to +12 degree Celsius air overhead. The result are high temperatures in the 60s to low 70s on Friday and Saturday.

Marine
Tonight... SW gusts 25-30 kt over south coastal waters will diminish this evening. 50 kt low level jet approaches southern waters overnight but should remain to the south. Potential for another round of 20-25 kt gusts over southern waters. Vsbys reduced in rain and fog.

Monday... N/NE winds under 15 kt with local sea breezes developing over nearshore waters in the afternoon. Increasing southerly swell in the wake of the low pressure will result in seas building to 5-7 ft over southern waters.

Monday night... Winds below SCA (Small Craft Advisory) with higher swell over southern waters slowly subsiding.

Outlook /Tuesday through Friday/... Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Thursday through Friday: Winds less than 25 kt.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
MARINE...
Small Craft Advisory until 2am EDT Monday for ANZ232. Small Craft Advisory until 11pm EDT this evening for ANZ233>235. Small Craft Advisory until 11pm EDT this evening for ANZ231. Small Craft Advisory until 8pm EDT this evening for ANZ236- 237. Small Craft Advisory until 8pm EDT Monday for ANZ254>256.