Vineyard Sound Marine Forecast
|Today...S Winds Around 10 Kt. Seas 2 To 3 Ft. Patchy Fog. A Chance Of Showers. Vsby 1 Nm Or Less, Increasing To 1 To 3 Nm This Afternoon.|
|Tonight...S Winds 5 To 10 Kt. Seas Around 2 Ft. Patchy Fog. A Chance Of Showers. Vsby 1 Nm Or Less.|
|Tue...S Winds 5 To 10 Kt. Seas Around 2 Ft. Patchy Fog. A Chance Of Showers. Vsby 1 To 3 Nm.|
|Tue Night...S Winds 10 To 15 Kt. Gusts Up To 20 Kt After Midnight. Seas 2 To 4 Ft. Patchy Fog. Showers Likely.|
|Wed And Wed Night...S Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 3 To 5 Ft. Showers Likely.|
|Thu...Sw Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 4 To 6 Ft. Showers Likely.|
|Thu Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 5 Ft.|
|Fri And Fri Night...Sw Winds 5 To 10 Kt. Seas 2 To 4 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.|
| Area Forecast Discussion|
National Weather Service Boston/Norton MA
358am EDT Monday September 28 2020
Increasingly moist southerly flow out ahead of a cold front will bring unseasonably mild conditions and scattered showers through Tuesday. A series of frontal systems will bring widespread, potentially heavy rainfall in two rounds from Tuesday night to early Thursday. More scattered showers are possible Friday but a cool dry weekend follows.
Near Term - Until 6pm This Evening
* Areas of locally dense fog early this morning. * An unseasonably mild day with overcast skies. Mostly dry except for some scattered showers, especially out towards the Cape and Islands.
A shortwave embedded in southwest flow has resulted in some scattered light showers across S New England early this morning, just enough to wet the roads for the most part. Otherwise, stout southerly flow advecting an anomalously warm air mass with dew points in the mid to upper 60s over ocean waters with SSTs in the low 60s have resulted in locally dense fog along the RI and MA south coast early this morning. Expect the fog to burn off shortly after sunrise.
Mostly overcast conditions will make for a gloomy day. We are still in a southwest flow out ahead of an approaching high amplitude upper level trough by mid week, which could turn out to be a drought- busting pattern change and usher in a much cooler air mass. But before then, we continue to be under the influence of a 580+ Dm upper ridge that will help continue the inflow of unseasonably mild and muggy air into New England. But other than some scattered showers except a heavier shower or two out towards the Cape, it should be a mostly dry, mild and muggy day. Have used a blend of models for highs given all the clouds that will be around. Highs mostly in the mid to upper 70s but would not be surprised to see some locations Probability of Precipitation into the low 80s if there are breaks in clouds. But it will be almost impossible to know when and where these breaks will occur at this time frame. Normal highs for late September range from the mid 60s to around 70. So most locations away from the immediate coast looks to run 10 to 15 degrees above average.
With the light pressure gradient in place, local sea breezes could develop for coastal locations, including Boston. This would also keep the highs lower in the low to mid 70s for these locations.
Short Term - 6pm This Evening Through Tuesday Night
Another mostly dry, muggy and mild night with an isolated shower. with winds from the south advecting air with dew points in the mid to upper 60s over waters with SSTs in the low 60s, there could be another round of widespread but locally dense fog.
One more muggy, mild and mostly dry day ahead of the cold front and a potential pattern change. Looks like bulk of the rain associated with the cold frontal passage will hold off till the evening hours. In other words, very similar to Monday and have continued to use a blended approach for the forecast. Eastern MA could see more sunshine than Western MA, so have trended temperatures warmer for the former and cooler for the latter.
Long Term - Wednesday Through Sunday
* Widespread, potentially heavy rainfall comes in two rounds from Tuesday night through early Thursday along with some gusty winds.
* There is another chance at showers Friday into Saturday but the weekend brings much cooler and drier weather.
Details... Tuesday night through Thursday... Things are falling into place to bring a prolonged period of potentially drought busting (or at least drought alleviating) rainfall to southern New England between Tuesday night and Thursday morning. This welcomed pattern change has been well advertised by global guidance for many days and confidence that we'll see some good rainfall somewhere in New England is high. That said, the location of the highest rainfall totals remains uncertain. The first round of more widespread rain comes Tuesday night into early Wednesday as a cold front stalls around eastern NY/western MA and a surface low rides up the stalled frontal boundary. Anomalously warm and moist southerly flow continues ahead of this front with PWATs (Precipitable Waters) approaching 2 inches, so there is plenty of moisture to work with. The highest rainfall totals (1 to 2 inches) with this round will likely be over western/central New England in closer proximity to the frontal forcing. Further east the potential for a decent soaking remains, but to a lesser degree. Again, confidence in the location of the highest Quantitative Precipitation Forecast remains low but confidence that we'll see a good rainfall is high. The moisture is there, as is the forcing; we're placed beneath the right rear quadrant of a 150 kt upper jet, with 40-50 kts at 925 mb as well.
The story is the same with the second round Wednesday night into Thursday, only this time the surface low is deeper and the low level jet is even stronger. The secondary surface low lifts up the east coast bringing strong forcing for ascent and the potential for another 1 to 2 inches somewhere over southern New England. The other impact would be potential for gusty winds Wednesday and Wednesday night. Model soundings don't show especially deep mixing, but depending on the track of the low and magnitude of the winds some decent gusts could reach the surface. This will also make for rough seas on area waters. There may be a decent gradient in high temps on Wednesday between western MA (50s) and eastern MA (mid 70s) depending on how far east that cold front can make it. Seasonable temperatures return Thursday in the upper 60s and low 70s.
Friday through Sunday
The cold front ushers in a cooler and drier airmass to end the week. The respite may be short lived as another low traverses the region Friday afternoon into Saturday morning bringing more rain chances. Beyond that, though, guidance is in good agreement that high pressure will bring dry and cool weather for the weekend.
A disturbance moving up from the Mid Atlantic coast will bring a chance of showers early this morning. Expect increasing south winds and building seas. Small Craft Advisory continues for some of the southern coastal waters due to marginal rough seas.
Scattered showers move off to the east Monday night. Reduced visibilities in patchy fog overnight. South winds less than 20 kt. Seas up to 5 feet on the exposed southern waters, less than 5 feet on all other waters.
Outlook /Wednesday through Friday/... Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 8 ft. Rain showers likely.
Wednesday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 9 ft. Rain showers likely.
Thursday: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain showers.
Thursday Night: Winds less than 25 kt. Areas of rough seas.
Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
Small Craft Advisory until 8pm EDT Tuesday for ANZ254>256.