Vineyard Sound Marine Forecast
| This Afternoon...W Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 2 To 4 Ft. |
| Tonight...W Winds Around 15 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. |
| Sun...Sw Winds Around 15 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. Rain. |
| Sun Night...S Winds 20 To 25 Kt, Becoming W After Midnight. Gusts Up To 35 Kt. Seas 4 To 7 Ft. Rain. |
| Mon...W Winds 15 To 20 Kt With Gusts Up To 30 Kt, Becoming Nw With Gusts Up To 20 Kt In The Afternoon. Seas 4 To 7 Ft. |
| Mon Night...N Winds 10 To 15 Kt. Gusts Up To 20 Kt In The Evening. Seas 3 To 5 Ft. |
| Tue And Tue Night...Ne Winds 5 To 10 Kt, Becoming S 10 To 15 Kt. Seas 2 To 3 Ft. |
| Wed...S Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. Rain Likely. |
| Wed Night...Sw Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 4 To 7 Ft. Rain. 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 1009am EST Sat Nov 26 2022 Synopsis High pressure building into Southern New England today will continue to produce blustery conditions, but temperatures to run around seasonable levels. Low pressure tracking to our west and north brings showers and gusty winds to our region late Sunday through early Monday. Mainly dry, tranquil weather extends through Wednesday ahead of a potent cold front sometime mid to late week. Near Term - Until 6pm This Evening 10 am Winds have picked back up after the boundary layer briefly decoupled this morning, now gusting generally 20 to 30 mph. Even so, winds have and will continue to diminish in magnitude through the day as high pressure moves in and the pressure gradient slackens. As such, the Gale Warnings have been taken down and replaced with Small Craft Advisories for all waters. Previous Discussion: Blustery, gusty northwest wind conditions prevail across Southern New England this morning, positioned in a tight NW gradient between approx 998 mb surface low pressure now over Nova Scotia and building surface ridging extending into NY and western New England. Doppler velocity wind profiler data from surrounding WSR-88D radars show 925 mb NW jet of 35-45 kt regionally. Much of this is being mixed to the ground under strong cold thermal advection steepening lapse rates. Gusts in the 25 to 35 mph range have been common, though have approached advisory levels in a few spots (e.g. some minor wind damage per spotters in Burlington, CT associated with estimated gusts 40-43 mph). Effects of sustained NW winds 15-20 mph and variable amounts of stratocumulus has led to current temps in the upper 30s to mid 40s, though the winds are nonetheless adding a bit of a chill. Moving ahead to today, blustery NW winds project to continue thru mid/late morning with gusts into the 20 to 30 mph range. Aforementioned surface ridging to then build across Southern New England late this morning thru the afternoon. which will shift winds to the W/WSW with continued gusts in the 20-25 mph range thru sundown. It's expected that gusts should ease upon and shortly after sundown. Sunny conditions given low PWATs (Precipitable Waters) prevail today with thermal advection quickly transitioning from cold to neutral/weak warm advection by the afternoon. All told, other than rather blustery conditions especially this morning, shaping up to be a nice day with highs in the 40s to low 50s. Short Term - 6pm This Evening Through 6pm Sunday 330am Update: Tonight: Warm thermal advection pattern becomes more marked tonight, with 925 mb temps warming to around +8 to +12C by 12z Sun. W to SW winds still look to be in the 5-10 mph range for the overnight, strongest further east one goes. Initially clear skies begin to fill will high to mid-level cloud decks for the second half of the overnight. This sets up a challenging low-temperature forecast. If winds can decouple/go calm for better radiational cooling, temperatures could fall pretty quickly and likely lower than what's currently forecast, especially in the CT Valley where lows are around freezing or a few degrees above that. Though onset of high to mid clouds occur later, better confidence in low temps in the mid 30s to low 40s across eastern MA and RI given stronger sustained SW winds. Temps seem likely to hover and rise in all areas by daybreak. Sunday: First part of Sunday features increasing and lowering cloud cover, with modest rises in temperatures and dewpoints. Focus however turns to the later afternoon hrs, as a deamplifying 500 mb shortwave disturbance in the southern branch of the jetstream and associated surface frontal system brings the potential for several issues to contend with: (1) windswept rains, some with local downpours SE of I- 95; (2) increasing, gusty south winds and building rough seas for mariners; (3) possible splashover or minor coastal flooding. Synoptics: occluding 990-ish mb primary cyclone moves through the St. Lawrence River Valley. However some bagginess to the isobars noted late day Sunday over the lower Hudson Valley infer possible secondary low pressure development. Impressive dynamic support and mid-level diffluent flow allows for fairly good ascent. Strong moisture advection noted on increasing SW 925-850 low level jet. This results in rising PWAT (Precipitable Water) values up to as much as 1.20 inches per 03z/26th SREF mean. PoPs/Wx: Soundings show lots of dry air below 700 mb thru 18z Sun, so the first half of the day should be on the dry side. Opted for sub-mentionable or low Probability of Precipitation thru early-afternoon. A then rather rapid west-east increase in Probability of Precipitation toward Categorical levels indicated as column saturates; given robust dynamics, moisture advection/rising PWATs (Precipitable Waters) and showalter indices approaching 0, potential exists for local downpours especially near the South Coast, Cape Cod and the Islands late-day Sunday (and carrying over into Sunday evening). It would especially be the case if secondary low does indeed develop. Winds/Gusts: Will see south winds steadily increase during the afternoon in most areas; 950 mb jet of 35-50 kt spreads northward 21z Sun-00z Monday across eastern/southeast MA and RI, with considerably lower in the interior. Despite the jet, mixing/momentum transfer looks to be limited with strongest core of the jet looking locked above temperature inversion; it's a situation that commonly happens in S/SW warm advection patterns is how much of the jet can we mix. Opted to keep gusts in the 25-30 mph range with the core of the jet not arriving until Sunday evening; suspect there will still be low end gale force gusts over the waters, which will produce pretty choppy and rough seas over the southern waters. Coastal Flooding Potential: See coastal flood section below. Long Term - Sunday Night Through Friday Highlights * Rainfall associated with an area of low-pressure exit southern New England Sunday night into Monday. * Gusty northwest winds Monday followed by cooler/dry conditions on Tuesday * Next low-pressure system approaches the region mid-week and brings rainfall to southern New England Wednesday and Wednesday night. Sunday night through Tuesday. Area of low-pressure moving over the Northeast will bring substantial rainfall to southern New England Sunday night, mainly before Midnight. Rainfall amounts will likely range from 0.25 to 0.5 inches for much of the region. Amounts greater than 0.5 inches will be possible over The Cape/Islands where a robust 50-60 knot low- level jet will move over an area with PWATs (Precipitable Waters) up to 1.2 inches. This will be a fairly progressive system, so we're currently expecting rainfall to end around or shortly after Midnight as this system ejects over the Atlantic Maritimes. Although there will be a very strong low-level jet at 925 hPa, surface wind gusts should largely be held in check by an inversion below the LLJ. Nonetheless, we may see some higher gusts from 30 to 40 mph mix down to the surface over The Cape and Islands. Gale headlines will likely be needed. Gusty northwest winds will carry into Monday with some clearing. Expect wind speeds to gradually diminish as the day progresses. We will still be in a pre cold frontal air mass with 925 temps above 0 Celsius. Thus, some mild temperature may be observed Monday afternoon, particularly over the eastern and southeastern areas where highs in the mid 50s will be likely. The surface cold front will push through the region Monday night with a much cooler and drier air mass. This will support dry/seasonable conditions on Tuesday. Wednesday through Friday Robust short-wave trough traversing across the CONUS will support the development of a fairly strong low-pressure system by the middle of next week. Southern New England may see WAA (Warm Air Advection - the movement of warm air) related precipitation as early as Wednesday afternoon before a robust cold front pushes through the Northeast Wednesday night into Thursday. This front will likely be accompanied by another round of substantial rainfall followed by strong post-frontal winds on Thursdays. This appears to be the most active period in the extended, so we'll be watching this system closely as we head into next week. High pressure builds in behind the front late week/early next week supporting dry/seasonable weather. Marine Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 330am Update: Overall high confidence. Headlines: Gale warnings continue on most waters, with small craft advisories for Boston Harbor and Narragansett Bay. Gale warnings can be downshifted to SCAs (Small Craft Advisories) as easing trends develop, likely mid morning to early afternoon. Looking ahead to later Sunday and Sunday night, Gale headlines will need to be considered in later updates; but given active gale warnings, opted to wait. NW gusts continue around 30-35 kt on most waters thru the morning. Winds then shift to W and trend more SCA-level late this morning to the afternoon. Easing winds/gusts anticipated tonight as winds turn more southerly. However winds steadily ramp up during the second half of Sun. Some question on mixing but potential exists for gale force S/SW gusts on at least the southern waters Sunday late afternoon and continuing into Sunday evening. Seas will turn increasingly rough later Sunday and Sunday night along with windswept rains. Outlook /Sunday Night through Wednesday/... Sunday Night: Low risk for gale force winds with gusts up to 35 kt. Areas of rough seas. Rain. Monday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Monday Night: Winds less than 25 kt. Seas up to 5 ft. Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Tuesday Night: Winds less than 25 kt. Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Rain likely. Tides / Coastal Flooding 330am Update: Splashover or minor coastal flooding is possible Sunday into Sunday evening associated with a frontal system. Coastal flood statements or advisories could be needed for both coasts. Astro tides remain elevated Sunday. Timing will be critical regarding this risk. Appears better overlap of southerly winds, an approximate 1.5 to 2 ft surge per Stevens Institute could favor the southern coastal waters/Narragansett Bay for the Sunday evening high tide (3.6 ft MLLW at Newport). May be some splashover in eastern MA around or just after the Sunday early afternoon tide (11.40 ft MLLW at Boston Harbor), but winds and surge don't look significant. While winds increase Sunday evening, the evening high tide looks lower (9.57 ft MLLW) and may not be as much a concern by then. NOAA Boston MA Office: Watches - Warnings - Advisories CT...None. MA...None. RI...None. Marine Small Craft Advisory until 1am EST Sunday for ANZ231>235-237- 250-251. Small Craft Advisory until 7pm EST Sunday for ANZ254>256. |
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