Vineyard Sound Marine Forecast (2024)

Synopsis
A cold front will move across the region late today and this evening and may be accompanied by a few showers or an isolated thunderstorm. Dry and seasonable conditions follow Friday with warming temperatures this weekend and early next week. The weather pattern then turns unsettled Tuesday and Wednesday with increasing chances of showers and perhaps a few thunderstorms.

Near Term - Until 6pm This Evening
630 AM

Widespread fog along the south coast will burn off during the next 2 hours as daytime heating/boundary layer mixing increases. However, expect lots of cloud cover this morning near the coast with some sunshine developing further in the interior. Cold front will be moving into SNE later this morning, reaching the I-95 corridor late this afternoon. Based on timing of front with max heating, the best chance for a few showers or t-storms will be near the I-95 corridor this afternoon, especially across RI and SE MA where CAPES increase to around 1000 J/kg within the pre-frontal environment.

The frontal passage will be followed by much drier air moving into the interior this afternoon as dewpoints fall into the 50s. These lower dewpoints will not reach the south coast until tonight.

Previous discussion... Synoptically, we'll finally see the beginnings of a pattern switch today as cold front approaches from the west. While pre-frontal storms and showers maintained overnight into the Albany area, as well as central NH, widespread showers failed to materialize across our area given a more stable environment driven by persistent cloud cover over the last 24-48 hours. With the front not forecast to cross our area until late this evening and the first half of tonight, do anticipate widespread clouds will inhibit substantial shower/storm development this afternoon, especially across interior MA and CT. The exception to this would be along the I-95 corridor between 17-20Z where, in light of overcast conditions, instability has the potential to grow in excess of 1000J/kg. With shortwave trough axis pushing into the region around the same time, there should be enough lift for showers and isolated thunderstorms to develop.

High resolution guidance is pretty consistent in the placement for showers/isolated storms this afternoon with the PVD to BOS corridor, southeast, having the best chance of seeing a wetting rain. Developing showers will feed off the prefrontal deep warm cloud depths, around 12000-13000ft and PWATs (Precipitable Waters) near 2", which could result in a quick half inch to an inch of rain falling over any lucky locality that ends up under a rather slow moving storm. HREF LPMM corroborates this thinking, showing isolated pockets of up to 0.75" of Quantitative Precipitation Forecast in the vicinity of SE MA and northern RI through 00Z this evening. Continue to ascertain that the threat for any severe weather this afternoon remains very low, with Storm Prediction Center placing only the eastern half of our CWA (County Warning Area) in a "general thunder" risk.

Short Term - 6pm This Evening Through 6pm Friday
Cold front pushes across the region in earnest after 00Z tonight with winds shifting from the SW to the WNW/NW behind the front; breezy conditions, with gusts up to 20kt, are possible right along the front this evening. Much drier air will rush into the region overnight with PWATs (Precipitable Waters) dropping to around 0.75". Anticipate the front will be seaward of the Islands by 06Z, but some patchy fog development in possible across the Cape prior to that time; though will dissipate quickly behind the front. Lows tonight will drop into the 60s, and perhaps upper 50s in NW MA.

Mid level trough will linger across New England on Friday but high pressure and height rises nudge in from the west. Strong ridging doesnt arrive until this weekend, but given the much drier column, anticipate a beautiful end to the work week with afternoon dewpoints falling into the 50s and high temps in the 80s. Clouds look to be far and few between as well; a welcome relief to those who found the last several days to be a bit too gloomy.

Long Term - Friday Night Through Wednesday
Highlights... * Dry conditions with warming temps this weekend into Monday but low risk for a few showers or a t-storm Monday afternoon

* Risk for showers and a few t-storms increase late Tuesday into Wednesday with increasing humidity

Details... Saturday through Monday... Mid level ridge builds across the Gt Lakes into interior New England this weekend while weak mid level low develops just offshore and eventually retrogrades into New England Mon. The column is dry this weekend so plenty of sunshine and dry conditions expected. Weak cold pool aloft under the upper low develops Monday with 500 mb temps cooling to -12 to -14C. The cooler temps aloft combined with increasing PWATs (Precipitable Waters) will will help to generate some instability with CAPES up to 1000 J/kg so can't rule out isolated showers/t-storm developing Monday afternoon. Deterministic GFS (Global Forecast System) and ECMWF (European Centre for Medium-Range Weather Forecasts) as well as ECMWF ensembles showing potential for some convection.

Warming temps this weekend into early next week but heat will be tempered by mid level low and developing cool pool aloft. Highs will reach well into the 80s and possibly near 90 in some interior locations Sunday and Mon, but a bit cooler along the coast as onshore flow develops. While it becomes a bit more humid as we head into Sunday and Mon, humidity levels will not be oppressive.

Tuesday and Wednesday... Pattern becomes more unsettled especially by Wednesday as next upstream trough approaches with PWATs (Precipitable Waters) exceeding 2 inches. Leading edge of this higher moisture moves in during Tuesday which will yield some risk for afternoon showers, but the best chance for showers/t-storms will be on Wed. A bit cooler Tuesday and Wednesday as cooling noted at 925 mb, but temps still in the 80s. Humidity levels will continue to increase Tuesday into Wednesday with dewpoints likely climbing into the low 70s by Wednesday within the tropical moisture plume.

Marine
Forecaster Confidence Levels:

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

Today.... High confidence.

Marine fog/stratus will linger for a good portion of this morning with more southerly winds. Isolated shower or thunderstorm possible along a cold front, with rapid clearing expected behind the front as winds shift more to the west. Seas remain below SCA (Small Craft Advisory) criteria between 2-4ft.

Thursday night...High confidence.

Cold front crosses the waters overnight. NW winds 10-15 kts. Seas 2-4 ft. Patchy fog possible ahead of the cold front that will dissipate by 06Z.

Friday... High pressure builds in with dry weather expected. Winds less than 25kt and seas 2-4ft.

Outlook /Friday Night through Monday/...High Confidence

Winds less than 25 kt.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...Dense Fog Advisory until 9am EDT this morning for MAZ019>023. RI...Dense Fog Advisory until 9am EDT this morning for RIZ006>008.

Marine
None.