Marine Weather Net

Rhode Island Sound Marine Forecast


THIS AFTERNOON

S
WINDS
20 - 25
KNOTS

TONIGHT

W
WINDS
10 - 15
KNOTS

SUN

NW
WINDS
5 - 10
KNOTS

SUN NIGHT

SE
WINDS
10 - 15
KNOTS

The Marine Weather Forecast In Detail:
ANZ235 Forecast Issued: 116 PM EST Sat Feb 27 2021

SMALL CRAFT ADVISORY IN EFFECT THROUGH SUNDAY EVENING
This Afternoon...S Winds 20 To 25 Kt With Gusts Up To 30 Kt. Seas 5 To 7 Ft. Patchy Fog. Rain. Vsby 1 Nm Or Less.
Tonight...W Winds 10 To 15 Kt With Gusts Up To 25 Kt, Diminishing To 5 To 10 Kt After Midnight. Seas 5 To 7 Ft. Patchy Fog. Vsby 1 Nm Or Less.
Sun...Nw Winds 5 To 10 Kt, Becoming E With Gusts Up To 20 Kt In The Afternoon. Seas 4 To 6 Ft. Rain Likely.
Sun Night...Se Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 4 To 5 Ft. Patchy Fog. Rain Likely. Vsby 1 Nm Or Less.
Mon...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 5 Ft. Patchy Fog. Vsby 1 To 3 Nm.
Mon Night...W Winds 15 To 20 Kt With Gusts Up To 25 Kt, Becoming Nw 20 To 25 Kt With Gusts Up To 40 Kt After Midnight. Seas 5 To 8 Ft.
Tue...Nw Winds 20 To 25 Kt With Gusts Up To 35 Kt. Seas 5 To 8 Ft.
Tue Night Through Wed Night...W Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 3 To 5 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
1248pm EST Sat Feb 27 2021

Synopsis
Snow quickly transitions to rain early today as a low pressure lifts through. Brief reprieve as high pressure builds in tonight. Rain returns Sunday into Monday, especially near the South Coast, as low pressure passes southeast of New England. Dry weather should prevail most of next week.

Near Term - Until 6pm This Evening
1 pm

Temperatures have risen well above freezing into the upper 30s and mid 40s across the region. As such, snow has transitioned to rain for everyone and this will continue until the back edge of precipitation moves from from west to east. Rain should come to an end 2-4pm for western MA/CT and 5-7pm for eastern MA/RI.

Previous Discussion... Highlights

* Snow to start off across most of southern New England today. Will quickly transition to all rain this morning.

Shortwave trough lifts from the central Great Lakes this morning into Quebec. Another subtle shortwave lifts from the TN Valley offshore of DE/NJ by this evening. A fairly broad low lifts across the eastern Great Lakes, Mid Atlantic and New England in response to these features. This brings a brief period of snow this morning before transitioning to all rain. Could see a dusting to an inch across the interior. Cannot completely rule out some local 2 inch amounts across the higher terrain of NW MA before changing to rain.

Still a tricky temperature forecast today. A secondary low develops along the south coast or over the region and lifts through. The secondary low lifting through should keep the ageostrophic component of the low level winds in a northerly component. This in turn helps lock in colder air in the lower levels, so it may be tough for the interior to see temperatures climb out of the 40s. Have leaned on the high res guidance in particular the ARW/NAMNest. Should warm into the mid to upper 40s and possibly a few 50s along the south coast due to the strong southerly warm air advection.

Anticipate that locations will transition over to all rain before noon, with it taking the longest across the higher terrain. This is shown well by low level warm air advecting in at 925 hPa. Starts off this morning at 0 to -3 degrees Celsius and increases to 0 to +6 Celsius by 18Z. Decent amount of Quantitative Precipitation Forecast across southern New England with totals between 0.25 to 0.75 inches. Expecting the highest Quantitative Precipitation Forecast along the south coast which coincides with where the strongest forcing is.

Other concern for today is strong winds. Still some differences amongst guidance in the strength of the low level jet that moves through. The high res guidance shows a 40-70 kt low level jet whereas synoptic guidance is more muted in the 40-60 kt range. Could be tough to mix down these stronger winds given the warm air advection should strengthen low level inversion. Have leaned on the HRRRE guidance as it tends to do well in these scenarios, so cannot rule out 20-30 kt gusts this afternoon across eastern MA and RI.

Lastly expecting fog across much of southern New England, but especially the interior. The precipitation changing over to rain will eat away at the snow pack. Have brought down visibilities across the interior to 1/2-3/4 of a mile where the snow depth is greater than 5 inches per the latest NOHRSC analysis. Not out of the question that fog could be a bit denser in spots.

Short Term - 6pm This Evening Through 6pm Sunday
Highlights

* High pressure briefly brings drier weather Saturday night.

* Rain returns to the forecast on Sunday.

Tonight... The shortwave lifts into Nova Scotia during the evening. Behind the wave, a ridge builds from the central Great Lakes into the eastern Great Lakes/Quebec. A weak high builds into the region.

Any lingering precipitation across eastern areas will taper off early in the evening as the system exits. High pressure briefly builds in and clears skies. However, will see increasing cloudiness late as the next system develops well to the SW/W of the region.

Should winds become relatively light with clearing skies for part of the night. Did knock down lows a bit in comparison to the previous forecast as there may be a bit of a window for some decent radiational cooling. Went with the 35th percentile of guidance, which results in lows in the upper 20s across the higher terrain of NW MA to the 30s elsewhere.

Sunday... Trough over the Northern Plains/Upper Mississippi River Valley early on Sunday lifts into Ontario by the evening. The surface low associated with this feature lifts across the Upper Midwest into Ontario, but the cold/occluded front lifts into southern New England.

Somewhat similar setup to today, however temperatures aloft are too warm for precipitation to start off as snow. This is expected to be an all rain event. Guidance continues to slow down the onset of precipitation, so have slowed down Probability of Precipitation in the latest update. Most areas may not see precipitation begin until the afternoon.

Temperature forecast is another tricky one as a secondary low may begin developing along the south coast. This should help keep the colder air locked in for parts of the interior. In addition, will have southeasterly flow which should help keep temperatures in the 40s elsewhere. So, highs range from the mid 30s across western MA to the mid 40s in SE MA/RI.

Long Term - Sunday Night Through Friday
Highlights... * Rain Sunday Night-Monday, especially near South Coast. * Dry for most of next week - brief shot of colder air Tuesday. * High uncertainty regarding possible coastal low for end of next week.

Overview:

Split mid level flow is expected to dominate across the U.S. through early next week before a transition to a mean trough over eastern third of country late next week. Still quite a bit of uncertainty in the details towards the end of next week. This uncertainty stems from the evolution of a mid level shortwave currently over the high latitudes of the North Pacific. It will be at least a couple of days before this comes into better focus.

Unsurprisingly, the 27/00Z GFS is the most progressive solution, leading to a more pronounced cutoff over the southeast U.S. late next week. Meanwhile most of the other medium range guidance is more of an open wave. Continue to have the greatest confidence in the forecast through Tuesday, with little confidence in the details for Thursday and Friday. Generally followed a consensus approach through this portion of the forecast.

Temperature-wise, expecting mainly above normal temperatures most of next week, with a significant exception. A strong mid level cold pool(a region of relatively cold air) should move across northern New England Monday night into Tuesday night. it will turn sharply colder, with below normal temperatures during this time. The cold does not stick around long, with above normal temperatures returning mid week. Near normal temperatures more likely towards next Friday.

Precipitation-wise, too warm for snow or sleet Sunday night into Monday. A touch of freezing rain towards the east slopes of the Berkshires is possible Sunday night into Monday. Once a triple point low pressure and cold front pass by Monday morning, expecting a drying trend Tuesday into Wednesday as a high pressure passes through. A weak cold front provides another chance for showers late Wednesday. Then the big question is how close a coastal low pressure can get to our region late next week.

Marine
Today and Tonight...High confidence

Have not made any changes to the Gale Warnings and Small Craft Advisories that were issued by the previous shift.

Southerly and southeasterly winds strengthen today as a system moves through. Winds shifting to the SW/W by this evening as the system exits. Winds shift to the NW tonight. Gusts of 20-30 kts this morning increase to 25-40 kts this afternoon. Expect the highest speeds where the Gale Warnings are in effect. The strong winds diminishing tonight as high pressure builds in. Waves build 4-7 feet this morning across the outer waters and 2-4 feet for the nearshore waters. Waves build to 6-9 feet this afternoon for the outer waters and 2-5 feet for the nearshore. Waves diminishing to 3-7 feet tonight with the highest heigheights over the southern outer waters.

Sunday...High confidence

Light and variable winds during the morning shift to the SE during the afternoon and increasing as the next system moves in. Waves 3-5 feet across the outer and southern waters.

Outlook /Sunday Night through Wednesday/... Sunday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain. Patchy fog. Areas of visibility 1 nm or less.

Monday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers, patchy fog.

Monday Night: Strong winds with gusts up to 40 kt. Rough seas up to 12 ft.

Tuesday: Moderate risk for gale force winds with gusts up to 40 kt. Rough seas up to 13 ft.

Tuesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas.
Wednesday: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain.

Tides / Coastal Flooding
Tides are astronomically high Monday, with Boston at 11.0 FT MLLW (12:36 PM), Nantucket 3.6 FT MLLW (12:02 PM), and Providence at 5.0 FT MLLW (9:23 AM). Current expectation is for a surge of less than one foot along the south coast, and perhaps around 1 foot along eastern MA coast, which would keep the total water level below the minor flood category for both coasts.

In addition, winds are expected to shift to the W/NW in the morning as a cold front moves offshore, lessening the potential along E MA coast. If front ends up slowing down, it is possible we could see minor splashover (sub-Coastal Flood Advisory level) along both coasts, but that seems to be a worst case scenario right now.

Does not appear to be a prolonged period of strong enough S/SE winds to build up seas offshore more than 4-5 FT, so beach erosion is not expected to be an issue right now either.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
MARINE...
Small Craft Advisory until 7pm EST this evening for ANZ232>234. Small Craft Advisory until 1am EST Sunday for ANZ231-251. Small Craft Advisory until 7pm EST Sunday for ANZ235-237-256. Gale Warning until 10pm EST this evening for ANZ250-254-255.