Rhode Island Sound Marine Forecast (2024)

Synopsis
Enjoy the warm and partly sunny conditions today, a backdoor cold front will bring much cooler conditions, clouds, and spot showers on Tuesday. The greatest risk for a period of showers will be Tuesday night into Wednesday morning. Temperatures for late this week and next weekend are uncertain given the positioning of a backdoor cold front...but are looking more likely to end up on the cooler side especially along the coast. After a slight chance of showers Thursday, another round of showers may arrive late next weekend.

Near Term - Through Tonight
A mixture of clear sky and some lower clouds early this morning. Fog and low clouds have been tough to come by, while there has been a few instances of isolated fog, do think there is enough mixing to preclude fog formation across southeast Massachusetts, Cape Cod, and the islands. Looking at the nighttime RGB product, can see some low clouds well to the northeast in the Gulf of Maine. While this feature is shifting from north to south, confidence in this reaching eastern Massachusetts remains low. The latest 07z HRRR (High-Resolution Rapid Refresh) does show the bank of low clouds/fog clipping the outer end of Cape Ann and Cape Cod between 5AM and 8AM. Something to monitor, though should have no real impacts - though, it could reduce visibility for our mariners.

Bigger picture, a weak area of high pressure at the surface and a mid-level ridge is centered aloft. There will be much drier air to our northeast into Maine, but we will hold on to a bit of mid-level moisture. A partly sunny day with should help to warm us into the 70s for many locations, but the immediate coast remains cooler. With a weak pressure gradient, do expect a sea breeze develops 10am to 12pm, the onshore flow limits the day time heating for those coastal communities. Essentially an east-northeast wind for the eastern coast of Massachusetts and a south-southeast wind for the southern coast of Rhode Island and Massachusetts. Wind speeds are 10 to 15 mph. Here temperatures are in the 50s to the low 60s. While further inland, a north-northwest wind will allow for minor downsloping in the CT River Valley, and could push temperatures close to 80 degrees. While this isn't a record, in fact the record for KBDL is 91F, set in 1974, but still, a high near 80F is warmer than the normal high of 67F.

Think the day will remain dry, but there is a low chance of a brief and localized shower for the locations southwest of Hartford due to the chance of convective showers developing north and west of the NYC Metro. HREF ensembles have a few hundred to a thousand units of surface based CAPE here in addition to PWATs (Precipitable Waters) one inch and better. Once again, this is Since there is high pressure, little steering for these storms and a good chance the will not drift towards our neck of the woods. As for now, kept the mention of any showers out of the forecast grids.

Increasing cloud cover post sunset as a 850mb warm front lifts from southwest to northeast. Can't rule out a few widely sct'd showers around midnight to 5/6am Tuesday. Maintained 20 to 40 POPs, 'Slight Chance' to 'Chance' POPs, mainly across northern Connecticut and western Massachusetts. A mild night as well with overnight lows in the upper 40s and low 50s.

Short Term - Tuesday
Highlights:

* Much cooler on Tuesday, by as much as 10 or 15 degrees cooler due to a backdoor cold front.

* Spot showers possible ahead of an approaching cold front late Tuesday.

A noticeable difference come Tuesday, temperatures are roughly 10 to 15 degrees colder than the day prior, plus cloudy skies and chance for spot showers. We can thank a backdoor cold front for the cooler temperatures, brought on by an east to east- southeast wind throughout the day. This knocks back the warm temperatures to a range of what is considered 'normal' for late April. There will be a spread in temperatures from the low/mid 50s in Boston to the mid/upper 60s in Hartford to Springfield. In between, many locations achieve a high temperature in-between the lower and middle 60s. Coastal towns are much cooler, with highs in the low to mid 50s! As for precipitation, have maintained 'Slight Chance' POPs across western Massachusetts and northwest Connecticut for the early afternoon, but the POPs increase into the late afternoon. Do think the bulk of any rain will arrive overnight, which is discussed in the Long Term section of the AFD.

Long Term - Tuesday Night Through Sunday
Key Points... * Cool Wednesday with highs in the 50s coast & 60s inland.

* Main threat for a period of showers Tuesday night into Wednesday morning.

* Generally dry Thu & Fri but can't rule out some scattered showers on Thursday...large spread in potential high temps.

* Another round of showers possible next weekend.

Details... Tuesday Night and Wednesday... High pressure remains in control directing cool, NE flow into southern New England keeping highs once again in the low to mid 50s (east) and mid 60s (CT valley). A shortwave passing overhead coupled with a surface low moving from the mid-Atlantic passing south of the region will bring a round of showers moving in Tuesday night and continuing through at least Wednesday morning; there is a low probability that showers continue well into the evening before weak ridging moves in and things dry out a bit.

Thursday And Friday
An upper level ridge tries to build in for the latter half of the week, but latest guidance now indicates a shortwave suppressing the eastern periphery of the ridge over SNE on Thursday, so things aren't looking as dry for Thursday as they did 24 hours ago. Even so, weak forcing and PWATs (Precipitable Waters) <1" will keep any rainfall from being to impactful. By Friday with the ridge closer dry weather is more likely. The biggest forecast challenge for this period will be the potential for another backdoor cold front to accompany this shortwave on Thursday which would keep the earlier expected 70s from materializing. At this point there is a considerable amount of uncertainty, but odds shifting toward a cooler solution with temps more likely to be in the 50s and 60s each day rather than the 70s.

Saturday and Sunday... The ridge axis arrives on Saturday with our next shortwave on its heels which brings the return of widespread rain chances as early as Saturday night. Confidence is low given significant spread in how the pattern evolves.

Marine
Forecaster Confidence Levels:

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

Through Tuesday... High confidence.

Low chance for coastal fog to develop early this morning across the eastern waters, nighttime RGB product does show an area of low clouds/fog across the Gulf of Maine and high-res model guidance shows the potential for this to drift south between 6AM and 10AM. Otherwise, dry and partly sunny Monday with east- southeast winds along the eastern coast of Massachusetts and south-southeast winds along the south coast of Massachusetts and Rhode Island. Winds are 10 to 15 knots and seas 2 to 4 feet.

Tonight winds are light and variable. Tuesday, winds are east to southeast 8 to 12 knots, gusts around 15 knots. Seas 1 to 3 feet. A few showers are possible ahead of an approaching front during the afternoon.

Outlook /Tuesday Night through Friday/... Tuesday Night: Winds less than 25 kt. Chance of rain showers, isolated thunderstorms.

Wednesday: Winds less than 25 kt. Chance of rain showers.
Wednesday Night through Friday: Winds less than 25 kt. Slight chance of rain showers.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.

Marine
None.