Narragansett Bay Marine Forecast
|Tonight...W Winds 5 To 10 Kt. Waves 1 Foot Or Less. A Chance Of Showers This Evening.|
|Sun...W Winds 5 To 10 Kt, Becoming Sw 10 To 15 Kt With Gusts Up To 25 Kt In The Afternoon. Waves Around 2 Ft.|
|Sun Night...Sw Winds 10 To 15 Kt With Gusts Up To 25 Kt, Becoming Se 5 To 10 Kt After Midnight. Waves Around 2 Ft. Patchy Fog. Showers. Vsby 1 To 3 Nm.|
|Mon...N Winds 5 To 10 Kt, Becoming Nw In The Afternoon. Waves 1 Foot Or Less, Except 3 To 5 Ft At The Bay Entrance. Patchy Fog. Showers Likely.|
|Mon Night Through Tue Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft, Except 3 To 5 Ft At The Bay Entrance.|
|Wed Through Thu Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves 1 Foot Or Less, Except 2 To 4 Ft At The Bay Entrance. 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
413pm EDT Sat May 8 2021
A few light scattered showers are possible late this afternoon into the evening, but most locations will stay dry. Mother's Day will feature seasonably mild and dry weather before a period of soaking rain overnight Sunday into early Monday morning. Rain tapers off on Monday. There could be a few isolated showers on Tuesday, but much of the week will be dry with slightly cooler than normal temperatures. Next potential shot for more widespread rain is late in the week into the weekend.
Near Term - Until 6am Sunday Morning
We remain under the influence of a negatively tilted H5 trough which continues to suppress any onset of prolonged warmth buildup. At the lower levels, we are caught in between a deepening low pressure to the south of Nova Scotia and an occluded low over NY state. Day Cloud Phase satellite imagery shows a deck of 3500-6000 ft stratocu deck associated with a light onshore flow associated with the cyclonic flow of a 988 mb surface low south of Nova Scotia.
With weak surface high pressure over our area under moist cyclonic flow, the result is plenty of mid-level clouds but very little rain, if any reaching the ground despite some reflectivity depicted on radar. 12z CAMs continue to suggest scattered showers developing late this afternoon into early evening, but most areas should stay dry. Therefore, have kept Probability of Precipitation at chance or less. Any showers that develop will end late this evening as weak surface ridging build into Southern New England overnight. This should lead to clearing skies after midnight. With light winds and dew points in the 30s, went with the 10th percentile of overnight lows to yield lows in the upper 30s to mid 40s.
Short Term - 6am Sunday Morning Through Sunday Night
Sunday... Much of Mother's Day is expected to be dry and seasonably mild. With deep mixing up to 750-800mb and 850mb temps +1 to +3C with southwest flow, used the 90th percentile to derive highs in the mid to upper 60s, except upper 50s to low 60s on the Cape and Islands as well as interior high terrain. These temperatures are right around climatological normals for the second week of May. Overall, a nice day to be outside to enjoy Mother's Day! Clouds will be on the increase though starting late morning from west to east but any rain should hold off till the evening hours.
Sunday night... * A period of soaking rainfall likely for much of the region overnight.
A mid level shortwave and surface low approach from the Ohio Valley on Sunday night into Monday bringing the returns of widespread rain chances, mainly Sunday night into Monday morning. The warm front lifts north after sunset on Sunday bringing isentropically forced rain showers to much of southern New England. The dynamics are impressive with good 925mb wind directional and speed convergence set up right over our region overnight. This front together with a PWAT (Precipitable Water) plume around 1 inch (75th percentile according to Storm Prediction Center sounding climatology for Chatham, MA) and 40-50 kt low level jet will bring a widespread decent soaking on the order of 0.25 to 0.75 inches under the heavier bands. Whether the heavier rain falls over the south shore or further north will still need to be refined in later updates, heavily dependent on the exact track of the low and surface warm front. It looks to be a quick hitter so we could be done with most of the rain by sunrise, with mid level dry air moving in from the west by the pre-dawn into the early morning hours.
Long Term - Monday Through Saturday
* Generally dry through the extended with slightly cooler than normal temperatures.
* Rain tapers off on Monday and there could be a few isolated showers on Tuesday. Next potential shot for widespread precipitation is late in the week into the weekend.
Monday... Shortwave trough over southern New England early on Monday will lift offshore. Another shortwave will quickly lift in from the central Great Lakes for late on Monday. A mid level ridge will build in for the afternoon and evening. At the surface, low pressure will lift from the south coast early on Monday to south of Nova Scotia by the afternoon. This will taper off rain showers as the low exits.
Temperatures are expected to be below normal for this time of year in wake of the system as colder air advects in. Should see H8 temperatures of 0 to +3 degrees Celsius overhead. This results in temperatures ranging from the mid 50s to low 60s.
Best chance for precipitation will be earlier in the day as the low pressure is moving out of the region. Could be a bit slow in bringing things to an end given the mid level dry air punching in. There could be enough low level moisture in place in combination with diurnal heating and the H5 shortwave lifting in for isolated showers during the afternoon. Have kept things in the slight chance category, but given the drier air aloft this could be a bit overdone.
Tuesday... H5 cutoff over the eastern Ontario/western Quebec will dig into the eastern Great Lakes and northern New England on Tuesday. A surface trough will swing through southern New England. Think that the combination of the upper cutoff, diurnal heating and surface trough could bring a few Probability of Precipitation up showers.
Have bumped up precipitation chances toward the latest SREF to keep a mention of isolated showers. Will be pretty difficult for widespread activity given PWATs (Precipitable Waters) between 0.25 to 0.5 inches, which is around the 10th to 25th percentile per Storm Prediction Center CHH Sounding Climatology. Best shot should be across the interior given it is closer to the upper forcing.
Temperatures moderating with 925 hPa air in the +5 to +7 degree Celsius range. Temperatures climbing into upper 50s and more widespread low to mid 60s.
Wednesday through Thursday... Cutoff/trough lifts out of the region early on Wednesday while a ridge axis builds into the central Great Lakes from the Upper Mississippi River Valley. The ridge will build into the central/eastern Great Lakes on Thursday. The surface high will nudge in from the central Great Lakes on Wednesday and build in on Thursday.
Dry and quiet weather expected through this period with temperatures continuing to moderate. Highs on Wednesday range from the upper 50s to mid 60s. By Thursday temperatures are getting to right around normal for this time of year with highs in the 60s.
Late Thursday through Friday... Lots of uncertainty this far out. Next trough lifts in from the central Great Lakes/OH Valley into the eastern Great Lakes/Mid Atlantic. Lots of spread amongst deterministic and ensemble guidance with the track of a surface low that develops in response to the trough. Too early for any details, but this could be the next shot for more widespread rain. Stuck with the NBM, which keeps things in the slight chance to chance range.
Weak high pressure near the Maritimes will maintain relatively light winds and seas across the waters, generally below Small Craft Advisory criteria through Sunday. The only exceptions are parts of the southern outer waters, where there may be isolated 5 ft seas and Small Craft Advisories are in effect. Then an area of low pressure approaches with periods of heavy rain at times overnight Sunday into early Monday morning. There could be brief periods of localized gusts up to 25 kt with areas of 5 ft seas.
Outlook /Monday through Thursday/... Monday: Winds less than 25 kt. Local rough seas. Chance of rain showers.
Monday Night: Winds less than 25 kt. Local rough seas.
Tuesday: Winds less than 25 kt. Seas up to 5 ft.
Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 20 kt. Seas up to 5 ft.
Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Wednesday Night: Winds less than 25 kt. Seas locally approaching 5 ft.
Thursday: Winds less than 25 kt.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
Small Craft Advisory until 8pm EDT Sunday for ANZ254-255. Small Craft Advisory from 5am to 8pm EDT Sunday for ANZ256.