Marine Weather Net

Narragansett Bay Marine Forecast


TONIGHT

N
WINDS
10 - 15
KNOTS

THU

N
WINDS
10 - 15
KNOTS

THU NIGHT

N
WINDS
15
KNOTS

FRI

N
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
ANZ236 Forecast Issued: 416 PM EDT Wed Apr 01 2020

GALE WATCH IN EFFECT FROM FRIDAY MORNING THROUGH LATE FRIDAY NIGHT
Tonight...N Winds 10 To 15 Kt With Gusts Up To 25 Kt. Waves Around 2 Ft. A Slight Chance Of Rain After Midnight.
Thu...N Winds 10 To 15 Kt With Gusts Up To 30 Kt. Waves 2 To 3 Ft. Rain Likely.
Thu Night...N Winds Around 15 Kt With Gusts Up To 25 Kt. Waves 2 To 3 Ft. Rain Likely.
Fri...N Winds 15 To 20 Kt With Gusts Up To 40 Kt. Waves 2 To 3 Ft. Rain Likely.
Fri Night...N Winds 15 To 20 Kt With Gusts Up To 30 Kt. Waves 2 To 3 Ft. A Chance Of Rain.
Sat And Sat Night...N Winds 15 To 20 Kt With Gusts Up To 25 Kt. Waves 2 To 3 Ft.
Sun Through Mon Night...Nw Winds 5 To 10 Kt. Waves 2 To 3 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
428pm EDT Wednesday April 1 2020

Synopsis
A large and intense ocean storm well southeast of New England this evening will pinwheel back toward the coastline Thu and Fri. This storm will bringing strong to possibly damaging winds and coastal flooding to coastal eastern MA especially Cape Cod and the Islands. In addition periods of rain, heavy at times will overspread the area Thu and Fri. Mainly dry weather returns for the weekend along with temperatures not as cool.

Near Term - Until 6am Thursday Morning
430pm Update ... Impressive circulation along with lightning well south of New England this afternoon with surface pressure somewhere in the 980s already! This occluded/vertically stacked low will move ENE overnight into eastern Georges Bank, well east of New England keeping most of the area dry. However cool and moist northeast flow will continue to generate scattered rain showers (possibly mixed with some wet snow overnight) mainly across southeast MA including Cape Cod and the Islands. Gusty NNE winds here up to 30-40 mph.

Elsewhere Mostly cloudy conditions will prevail along with a spot rain/snow shower possible. The exception will be across the CT River Valley where scattered to broken diurnal clouds will likely erode with sunset and then fill back in with clouds from RI and eastern- central MA. Clouds and NNE winds shifting to NNW will limit min temps overnight to the 30s...right on track for early April.

Short Term - 6am Thursday Morning Through Thursday Night
430pm update ... Thursday ... Vertically stacked 980ish mb low well east of Nantucket around 40N/60W 12z Thu, begins to retrograde westward courtesy of -NAO blocking pattern downstream. This results in this large and deep circulation tracking westward toward the Gulf Maine and its associated TROWAL precipitation backing into MA/RI/CT as the day progresses with rain fairly widespread by late in the day.

Ptype mainly rain but marginal temps aloft may support some wet snow mixing in at times if precipitation intensity allows wet bulb temps to be realized. Again, mainly a rain event here. Another cool day with highs only in the 40s but low 50s possible across CT given rain delayed there until late in the day. Chilly north winds with gusts up to 30 mph except up to 45 mph over Cape Cod and the Islands.

Thursday night ... Model guidance has trended farther west with ocean low and now expected to make its closest approach toward 12z Fri, near the 40N/70W benchmark. Model soundings and wind fields suggest 55-60 kt low level NE jet moving across Cape Cod and Islands toward 12z Fri. Thus have hoisted a High Wind Watch for this area given the potential for wind gusts near 60 mph. Periods of rain, heavy at times continue especially across eastern MA and RI. Lows mainly 35- 40, low 40s Cape Cod and Islands.

Coastal flooding ... Had a one foot observed storm surge this morning at Nantucket. ETSS and ESTOFS only offering a 1 foot surge Thu morning despite increasing onshore winds tonight. Stevens Institute surge ensembles suggest closer to a 2 ft surge possible. This would bring storm tide close to flood stage. This combined with 4-6 ft wave action ontop of the surge suggest minor coastal flooding likely. Thus have issued a Coastal Flood Advisory for Nantucket Thu morning high tide. Little if any flooding expected elsewhere.

For Fri, astro high tide slightly higher but given core of strong winds will occur around 12z expecting NNE winds gusting up to 60 mph to generate a 2-3 ft surge. This places most of the eastern MA coastline in a moderate flood category with greatest risk Cape Cod communities to Nantucket. In addition greater wave action expected as well with 15-20 ft seas ocean waters east of Nantucket and Cape Cod. Low risk for seas up to 25 ft seas Fri morning. These dangerous seas will be long period/high energy waves. Thus to highlight this threat of moderate coastal flooding have issued a coastal flood watch for Fri morning high tide for the entire coastline. Again greatest risk across Cape Cod and Nantucket. Keep in mind highest astro tides are in the morning vs evening tide cycle.

Long Term - Friday Through Wednesday
Highlights... *Powerful offshore storm will bring periods of rain and high winds to much of the area Thursday and Friday.

*Lingering showers on Saturday before drying out by Saturday afternoon. Sunday looks to feature mostly dry conditions with moderating temperatures.

*Seasonable conditions for first part of the work week with occasional chances for showers.

Details... Friday... The huge ocean storm will continue to retrograde on Friday, bringing periods of rain and high winds to much of Southern New England. This is in response to a highly amplified and blocky synoptic pattern over the higher latitudes, resulting in a deep and slow-moving 500mb trough over the Atlantic Ocean. By Friday morning, as the warm front wraps around the retrograding surface low, a northeasterly low level jet will develop and intensify to 60-65 kts at 925mb over Eastern MA. Given that Bufkit soundings show mixing up to around 900mb and momentum transfer of up to 55 kts, have gone ahead and issued High Wind Watches over the Cape and Islands. By Friday afternoon, conditions are forecast to improve slowly from west to east. There may even be enough breaks in the clouds to support temperatures in the upper 40s and lower 50s in Western MA and CT while rainy and raw conditions continue in Eastern MA and RI.

Saturday into Sunday... A warming trend begins early Saturday as a broad 500mb ridge slowly builds in from the west. There remains questions on how quickly the aforementioned trough will be able to move out of the way. Moreover, remnant pieces of shortwave energy from the exiting trough look to linger for occasional showers and plenty of clouds.

Sunday looks to be the nicer day of the weekend as a broad surface high pressure builds in from the mid-Atlantic states, Temperatures could overperform especially near and along the CT River valley on Sunday, which looks most likely to be in the warm sector out ahead of a cold front. The ECMWF (European Centre for Medium-Range Weather Forecasts) has 925mb temperatures of around +7 to +9C in Western MA and CT. Using pattern recognition, have bumped up the high temperatures on Sunday especially in Western MA and CT to mid and upper 50s. Models are also hinting at some elevated instability with about 20-25C of K Index and mid-level lapse rates of 6 to 6.5C/km. However, given we are still 4 days out and the timing of the aforementioned cold front is still in question, have only mentioned the chance of showers for late Sunday into early Monday.

Monday into Wednesday... We remain in a broad 500mb ridge pattern for the first half of the work week so despite the passage of the weak cold front late Sunday into Monday, Monday is expected to feature above average temperatures. Normal highs for early April are generally in the lower to mid 50s. For Tuesday and Wednesday, however, enough disorganized pieces of shortwave will head our way from time to time to lend moderate confidence to the forecast at best. So have gone with a blend of guidance for this part of the forecast, which yields generally seasonable conditions and occasional showers.

Marine
430pm update ... Ocean storm well south of New England Wednesday afternoon will track ENE to near 40N/60W Thu but then retrograde westward back toward 40N/70W benchmark 12z Fri. This will be accompanied by 55-60 kt low level NE jet at 2-3 kft above sea level surface. Thus potential NE storm force winds late Thu night into Fri. Long fetch will develop dangerous seas of up to 25 ft east of Cape Cod and Nantucket by 12z Fri.

Outlook /Friday through Monday/... Friday: Low risk for storm force winds with gusts up to 50 kt. Rough seas up to 23 ft. Rain likely.

Friday Night: Strong winds with gusts up to 45 kt. Rough seas up to 21 ft. Chance of rain.

Saturday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 17 ft. Slight chance of rain.

Saturday Night: Winds less than 25 kt. Rough seas up to 12 ft.

Sunday: Winds less than 25 kt. Rough seas up to 10 ft.

Sunday Night: Winds less than 25 kt. Areas of rough seas. Slight chance of rain.

Monday: Winds less than 25 kt. Local rough seas.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...Coastal Flood Watch Friday morning for MAZ007-015-016-019- 022>024. Coastal Flood Advisory from 6am to 10am EDT Thursday for MAZ024. High Wind Watch from Friday morning through late Friday night for MAZ022>024. RI...None. MARINE...Storm Watch from Friday morning through late Friday night for ANZ231-232-250-254-255. Gale Watch from Friday morning through late Friday night for ANZ230-233>237-251-256.