Rhode Island Sound Marine Forecast
| Today...Sw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 5 Ft. Rain This Afternoon. |
| Tonight...S Winds 25 To 30 Kt, Becoming W 20 To 25 Kt After Midnight. Seas 6 To 9 Ft. Rain. Vsby 1 To 3 Nm. |
| Mon...Nw Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 5 To 8 Ft. |
| Mon Night...N Winds 15 To 20 Kt, Diminishing To 10 To 15 Kt After Midnight. Gusts Up To 25 Kt. Seas 4 To 6 Ft. |
| Tue...N Winds 5 To 10 Kt, Becoming Se In The Afternoon. Seas 2 To 3 Ft. |
| Tue Night...S Winds 5 To 10 Kt, Increasing To 10 To 15 Kt After Midnight. Seas Around 2 Ft. |
| Wed...S Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 5 Ft. Rain. |
| Wed Night...Sw Winds 20 To 25 Kt With Gusts Up To 35 Kt. Seas 6 To 9 Ft. Rain. Vsby 1 To 3 Nm. |
| Thu...W Winds 20 To 25 Kt With Gusts Up To 30 Kt. Seas 7 To 8 Ft. A Chance Of Rain. |
| Thu Night...Nw Winds 20 To 25 Kt With Gusts Up To 30 Kt. Seas 4 To 7 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. |
| Area Forecast Discussion National Weather Service Boston/Norton MA 639am EST Sunday Nov 27 2022 Synopsis Increasing clouds today as low pressure tracking to our west and north brings rain, gusty winds and possible minor coastal flooding to Southern New England tonight. A cold front moves through on Monday, and while its passage will be a dry one, it will make for blustery conditions later 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 630am Update Forecast remains on track at this hour and no changes are needed. See previous discussion for more details. Previous Discussion 428am Update: In-situ surface ridge remains established early this morning from surface high pressure over coastal NC. Southern New England is entrenched in a SWly warm thermal advection pattern ahead of a well- developed frontal system over the mid-MS Valley. Infrared satellite imagery reveals a considerable stream of warm-conveyor-belt-related cloudiness across the OH Valley and Appalachians; the northeast extent of which was beginning to impinge upon our western counties. Current temps ranged from the mid 30s in the Pioneer Valley of northwest MA to the mid 40s-lower 50s across eastern portions of Southern New England where SW gradient winds continue. Approaching frontal system will serve as the focus for active weather for the late this afternoon into the tonight forecast. More details to follow on that in the short term forecast section below. Until then, initially generally filtered high clouds will continue to thicken and lower as we move through the day. Will also see southerly winds gradually increase and especially late afternoon across southeast New England. Dry profiles below cloud base should hold off approaching rains until after sundown (around/after 20z) and later further east. The cooler start in northwest MA along with reduced insolation from cloud cover should support highs in the upper 40s, with lower to middle 50s across eastern MA where some peeks of sun develops thru filtered sunshine. Finally, we do have active coastal flooding headlines in effect for the Sunday late-morning high tide, with coastal flood statements for the North Shore to Boston Harbor, and coastal flood advisories for minor coastal flooding for Cape Cod and Nantucket. There have been no significant changes regarding these coastal flooding headlines; these are largely driven by elevated astronomical tides with this morning's high tide predicted to feature the largest astro tides of the day. While storm surge should prove limited given that winds and waves don't pick up until later tonight, splashover or very minor coastal flooding is possible. Short Term - 6pm This Evening Through 6pm Monday 428am Update: Tonight: Active weather becomes centered in the tonight forecast period, as potent mid-level shortwave disturbance and related frontal system near and clear through Southern New England. There are several weather-related issues to concern ourselves with, although none should prove especially significant or major. Those are: (1) wind- swept rain with brief heavy downpours, possible thunder? (2) gusty south winds for the South Coast, Cape Cod and the Islands (3) hazardous marine conditions and (4) splashover or very minor coastal flooding associated with the Sunday evening high tide along Narragansett Bay and the shoreline of Buzzards Bay in south coastal MA. Synoptics-wise: primary cyclone occludes as it moves thru the St. Lawrence Valley, with possible secondary low development in vicinity of a triple-point near the Hudson Valley early tonight, which rides NE on the nose of a dryslot seen well in water vapor imagery over the lower MS Valley. Pretty healthy dynamics and mid- level diffluent flow characterize this system, with strong moisture advection driving PWAT (Precipitable Water) values to anomalously elevated values of 1.1-1.4" per the 03z/27th SREF mean. 850 mb jetstreak of 65-70 kt with 950 mb jet of nearly 50 kt oriented along south coastal MA/RI and Cape Cod between 00-06z Monday. Rain and Amounts: Rain likely will be ongoing across western portions of MA/CT, but Probability of Precipitation ramp up quickly to Categorical levels for the first part of the evening. Rain could prove heavy at times given the dynamics elevated PWAT (Precipitable Water) values; did note some neutral to weakly negative showalter indices and most-unstable CAPE values of a couple hundred J/kg late this evening in southeast New England. Not out of the question that thunder could develop but likely the exception vs the rule. Dryslot races in late evening to early overnight, which should bring an end to additional rainfall, though cloudiness will be tough to fully shake free of. Event total rainfall around one-half to nearly an inch, especially where sustained downpours can develop. Winds and Wind Gusts: Modest southerly breezes should prevail for most of the interior, but the focus for stronger SW gusts lies along south coastal MA/RI and Cape Cod/the Islands from roughly early evening to midnight. Mixing remains a question mark given most of the strongest low level jets are locked above an inversion; however did note in this morning's guidance that the jets did show an increase of around 5 to 10 kt. Thus did boost gusts up a smidge more and bring gusts to just under Advisory levels (40 to 45 mph). Could be possible some very minor/isolated wind damage occurs from gusts at this level. Even if winds continue to increase in later forecasts to support a possible wind advisory headline, limited impact likely would not change much unless there is a marked increase in the jets or if mixing is better than anticipated. That trees have lost most of their leaves also renders a generally minor impact, too. Should see southerly gusts 25 to 30 mph up to I-95, and much less further north and west. Low level jets move eastward after 06z, which should support gradually less-gusty conditions. Coastal Flooding: Focus turns to the south coast for the evening high tide, where lower astro tides may be offset by storm surge up to 2 ft in spots in Narragansett Bay and Buzzards Bay. More detail in the amended coastal flooding section. Monday: Looking like more clouds than sun early on Monday, ahead of a cold front aloft that moves SE through Southern New England between 15 to 21z. Temperatures should rise into the mid 40s to lower to mid 50s by early afternoon. Falling temperatures and increasingly breezy northwest winds develop in the wake of the cold front for the afternoon, with NW gusts around 25 to 30 mph. Long Term - Monday Night Through Saturday Highlights * Cool/dry conditions Tuesday followed by above normal temperatures on Wednesday. * Strong cold front pushes through New England Wednesday night into Thursday with potentially heavy rainfall and gusty winds. * Gusty post frontal winds and dry conditions Thursday will be followed by quiet weather early next weekend as high pressure builds over the eastern US. Monday Night and Tuesday A mid-level ridge axis builds over the Northeast on Monday night with northwest flow and Cold Air Advection aloft. This will usher cooler/drier air over the region and set the stage for a dry but cool day on Tuesday. Setup is favorable for efficient radiational cooling with light winds and clear skies Monday night. Lows Tuesday morning will likely be at or below freezing for most of interior southern New England. Cool/dry conditions carry into Tuesday afternoon as high pressure moves overhead. 0 Celsius temps at 925 hPa will translate to surface temps in the mid to upper 40s which is slightly below normal for late November. Wednesday and Thursday Mid-level ridge axis builds east of southern New England Tuesday night into Wednesday and induces return flow from the south/southwest. This will be associated with strong WAA (Warm Air Advection - the movement of warm air) that will allow temperatures at 925 hPa to rise between 5 and 10 Celsius by late Wednesday afternoon. As a result some areas in southern New England will experience well above normal temperatures. Highest temps will be observed across east and southeastern MA where 60 degree highs temps are not out of the question. WAA and southwest flow will come with increasing moisture and cloudiness Wednesday as well. Guidance has backed off a bit in terms of WAA related precipitation across southern New England early Wednesday. This is in large part due to dry air in the 850 - 700 hPa layer. Latest guidances suggests the column will not saturate until early to mid afternoon Wednesday, at which time we'll begin to experience WAA related precipitation ahead of a strong cold front. Precipitation will become more intense Wednesday night as the strong surface cold front pushes through the Northeast. Forcing looks to be strong as latest guidance has resolved impressive jet dynamics with a 60 knot low-level jet developing at 850 hPa. Moisture on the other hand is more modest with model PWATs (Precipitable Waters) coming in slightly below an inch. Ensemble precipitation products suggest accumulations of half an inch or more are possible. Accumulation details will be ironed out as the event draws nearer.There is fair agreement among model guidance that the front and associated precipitation will be clear of southern New England by day break on Thursday. Another concern with this frontal passage will be the potential for headline worthy wind gusts. 12Z EPS ensemble guidance suggests a 20 to 40 percent chance of 55 mph wind gusts over The Cape and Islands as the front moves through late Wednesday night. Strong post frontal- wind gusts are likely to carry into Thursday with Cold Air Advection developing behind the front. This should support a cool and blustery day on Thursday. Friday and Saturday Strong wind gusts diminish by Friday as high pressure builds over the Northeast. This will support dry and seasonable weather for at least the first half of next weekend. Marine Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High - greater than 60 percent. 428am Update: Overall high confidence. SCA (Small Craft Advisory) remain in effect until 4pm for the southern ocean waters due to marginal SW gusts and seas 3-5 ft. However period of greatest impact for mariners begins around 21z Sunday. The existing Gale Watch has now been converted to Gale Warnings, and the SCA (Small Craft Advisory) over the southern nearshore waters has also been upgraded to Gale Warnings. Gale Warnings run from 21z Sunday to 11z Monday. On the eastern/northeast waters, SCAs (Small Craft Advisories) have been issued from 00z to 12z Monday. Southerly winds will continue to ramp upward today on the southern waters, and begin to increase later this afternoon on the eastern waters. Gale conditions appear likely for all southern waters for tonight, along with windswept rains and increasingly rough seas to between 6 to 10 ft. Such conditions could be dangerous to mariners traversing the southern waters tonight. Should see wind gusts come down to around 30 kt late overnight to early Monday morning. A cold front moves over the waters on Monday. WSW winds at SCA (Small Craft Advisory) criteria gusts should shift to NW at around 25 to 30 kt on all waters. This will mean that SCAs (Small Craft Advisories) (both existing and to be issued once gale conditions ease) will likely need to be extended beyond 12z Monday. Outlook /Monday Night through Thursday/... Monday Night: Winds less than 25 kt. Seas up to 5 ft. Tuesday: Winds less than 25 kt. Seas locally approaching 5 ft. Tuesday Night: Winds less than 25 kt. Wednesday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Chance of rain. Wednesday Night: Strong winds with gusts up to 40 kt. Rough seas up to 11 ft. Rain. Thursday: Strong winds with local gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of rain. Tides / Coastal Flooding 428am Update: Coastal flood advisories remain in effect for Cape Cod and Nantucket, and coastal flood statements remain in effect for North Shore to Boston Harbor. Elevated astro tides (11.40 ft MLLW at Boston Harbor/4.41 ft MLLW for Nantucket) with generally limited storm surge at one ft or less for the early afternoon tide will support minor splashover or minor coastal flooding. Typically coastal flood prone shoreline roads, such as Morrissey Blvd in Boston and Easy Street on Nantucket are at risk of seeing tidal flooding with the early afternoon high tide. A coastal flood statement has also now been issued for counties adjacent to Narragansett Bay as well as Buzzards Bay for the Sunday evening high tide. Astro tides are lower with this high tide period (approximately 1030 PM), with tides of 3.59 ft MLLW at Newport and 4.50 ft MLLW at Providence. Latest forecasts and Stevens Institute surge guidance shows a 1.5 to 2 ft storm surge that could offset the lower astro tides. Looks like this peak surge occurs close to or just before the high tide tonight; which led to the choice of a coastal flood statement for minor splashover. However if surge becomes more synced with high tide, minor coastal flooding supporting a possible upgrade to Advisory could be needed. Stevens Institute actually shows water levels in the minor coastal flooding category for Providence. NOAA Boston MA Office: Watches - Warnings - Advisories CT...None. MA...Coastal Flood Advisory from 11am this morning to 4pm EST this afternoon for MAZ022-024. RI...None. Marine Small Craft Advisory from 7pm this evening to 7am EST Monday for ANZ230-231-236-250-251. Gale Warning from 4pm this afternoon to 6am EST Monday for ANZ232>235-237-254>256. Small Craft Advisory until 4pm EST this afternoon for ANZ255- 256. |
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