Marine Weather Net

Buzzards Bay Marine Forecast


OVERNIGHT

E
WINDS
10 - 15
KNOTS

THU

SE
WINDS
10 - 15
KNOTS

THU NIGHT

SW
WINDS
5 - 10
KNOTS

FRI

SW
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ234 Forecast Issued: 1027 PM EDT Wed Aug 04 2021

SMALL CRAFT ADVISORY IN EFFECT FROM 2 AM EDT THURSDAY THROUGH THURSDAY EVENING
Overnight...E Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas Around 2 Ft. Patchy Fog. Showers With A Slight Chance Of Tstms. Vsby 1 To 3 Nm.
Thu...Se Winds 10 To 15 Kt, Becoming S In The Afternoon. Gusts Up To 25 Kt. Seas 2 To 4 Ft. Patchy Fog. Showers. Vsby 1 To 3 Nm.
Thu Night...Sw Winds 5 To 10 Kt. Seas 2 To 4 Ft. Patchy Fog. A Chance Of Showers. Vsby 1 To 3 Nm.
Fri...Sw Winds 5 To 10 Kt. Seas 2 To 4 Ft.
Fri Night Through Sat Night...Sw Winds 5 To 10 Kt. Seas 2 To 3 Ft.
Sun Through Mon Night...S Winds 5 To 10 Kt. Seas Around 2 Ft. Winds And Seas Higher In And Near Tstms. 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
1013pm EDT Wednesday August 4 2021

Synopsis
A front moves onshore this evening into Thursday bringing showers and thunderstorms with locally very heavy rainfall and possible flooding. Drying out Thu night. Summer warmth and humidity returns late this week into next week. Dry weather expected on Friday into early Saturday. Will have more of a summer pattern in place late on Saturday into early next week with isolated to scattered showers/storms most days.

Near Term - Until 6am Thursday Morning
10 PM

Mainly light to moderate showers lifting north across RI and SE MA this evening within the right entrance region of the upper jet. Some heavier showers just south of New Eng which will be moving through, but peak of the heavy rainfall will occur late tonight into Thu. This occurs at the nose of the developing low level jet which lifts north toward SE New Eng with subsequent increasing PWATs (Precipitable Waters) to 2"+, along with added low level convergence along the surface boundary which will move into SNE from the SE. Based on position of low level jet and PWAT (Precipitable Water) axis, it appears axis of heaviest rainfall may be focused more along and east of the I-95 corridor across RI and SE MA where boundary sets up with wave tracking along it. However, until we see latest radar trends later tonight can't rule out heavy rain a bit to the west so no changes to current forecast. The heavy rainfall across SE New Eng will likely persist into Thu afternoon.

Previous discussion... Much of southern New England remains dry, if cloudy, this afternoon, with the exception being southern Rhode Island and southeast Massachusetts. Here the light to moderate rainfall has begun which will kick off a 18 to 24 hour period of rainfall. Zooming out a bit southern New England is sandwiched between a subtropical ridge over the east Atlantic and a deep trough over the Ohio Valley. These features are clearly visible on water vapor satellite as this digging trough amplifies the downstream ridging and funnels a firehose of tropical moisture up the east coast. At the same time a series of surface low pressure centers will be moving up from the Mid Atlantic into New England overnight and Thursday. We have ample moisture and dynamics for widespread rainfall; PWATs (Precipitable Waters) push up above 2 inches with dewpoints in the mid to upper 60s, near 70 F. The right rear quadrant of a 90-100 kt upper jet overhead provides broad forcing for ascent while dynamics are also favorable in the low/mid levels with a 40-50 kt jet and low level convergence associated with the surface low. The difficult part at this moment is the unusual degree of discrepancy in both timing of the low centers/jets and heaviest precipitation placement. For instance, the latest NAM guidance wants to bring a second low level jet and band of heavy precipitation well into Thursday afternoon. Given that it remains an outlier amongst other deterministic guidance as well as the EC and GFS ensemble guidance, we'll continue to message the heaviest rain occurring generally 11pm to mid morning on Thursday. The further west you go, the more uncertain things get, as this system will likely have a very tight gradient between who sees next to nothing and who sees several inches of rain. Generally, the axis of heaviest rainfall should be along the I-95 corridor where 1 to 3 inches is possible, up to 4 inches locally. If several inches of heavy rain fall in a short time, we are primed to see urban and small stream flooding issues. Fortunately much of the heaviest rain will be overnight, but it likely will linger into the Thursday morning commute. A Flash Flood Watch has been issued for much of eastern Massachusetts, Rhode Island, and far eastern Connecticut for this reason. We'll also have some instability with this system overnight with 500-1000 J/kg of MUCAPE over southeast MA and 25-35 kts of 0-1 km shear. So, we'll likely hear some rumbles of thunders, and given the favorable instability and shear, together with low LCLs and boundaries nearby, we can't rule out of low probability of a rotating storm.

Short Term - 6am Thursday Morning Through Thursday Night
Thursday things should be improving, but perhaps not as quickly as previously thought. The best chance of dry weather will be western Massachusetts and Connecticut, further removed from the series of surface lows that continue to slide up the frontal boundary. These will bring continued chances for showers from Worcester eastward, though rainfall amounts won't be as robust. PWATs (Precipitable Waters) finally come down late Thursday as the trough axis approaches and crosses the region overnight. This will finally bring a dry period Thursday night into Friday. Don't expect a lot of sun on Thursday, but skies will begin clearing from west to east by mid afternoon. The airmass overhead (850 mb) will be a bit warmer on Thursday, but with the rain, cloudcover, and poor mixing, temperatures will likely we a bit cooler than today, in the low to mid 70s.

Long Term - Friday Through Wednesday
Highlights

* Generally looks like dry and quiet weather through much of the extended with a return of summer heat and humidity. Could have isolated to scattered showers/storms Saturday through Tuesday mainly during the day.

Friday into Saturday AM... Trough over New England early on Friday will lift into Nova Scotia, while a ridge axis builds into the Mid Atlantic from the Southeast US. The ridge builds into southern New England late on Friday before shifting offshore early on Saturday. High pressure builds into the region from the Mid Atlantic.

Should see any lingering precipitation across Cape Cod and the Islands come to an end early on Friday as the trough exits and high pressure builds in. Dry and quiet weather expected. Becoming more humid as flow aloft becomes more southwesterly advecting in mid to upper 60 degree dewpoints. Summer time heat returns with 925 hPa temps of 20-22 Celsius. The result are readings in the 80s across southern New England.

Saturday afternoon through Tuesday... Shortwave trough lifts in from the eastern/central Great Lakes later on Saturday before exiting on Sunday. Ridge builds in behind the shortwave and moves offshore early next week. This will allow the next shortwave to lift into the region from the Great Lakes region early next week. Most locations will remain dry and quiet through this stretch, but with the heat/humidity and some lift there will likely isolated to scattered showers/storms around during the afternoon and into the evening.

The summer warmth continues through the weekend into early next week with most days having prolonged southerly flow. The only exception is on Sunday and Monday were it will be bit cooler as a shortwave exits and ridge builds in from the west. This will result in W/NW flow aloft bringing temperatures into the low to mid 80s versus mid to upper 80s.

Not anticipating any washouts during this stretch, but there will be a better opportunity for more widespread precipitation late on Tuesday or on Wednesday as a front moves in.

Marine
Forecaster Confidence Levels.

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

Moderate Confidence through Thursday night.

Wind and seas remain below SCA (Small Craft Advisory) thresholds today. Approaching low level jet will bring increasing south winds with gusts to 25-30 kt later tonight into early Thu with building seas over south coastal waters. Vsbys reduced in showers and fog tonight into Thu morning. A few t-storms possible.

Outlook - Friday through Monday
Friday: Winds less than 25 kt. Seas up to 5 ft.

Friday Night through Saturday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.
Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft.

Monday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...Flash Flood Watch through Thursday morning for CTZ004. MA...Flash Flood Watch through Thursday morning for MAZ005>007- 012>021. RI...Flash Flood Watch through Thursday morning for RIZ001>008.
MARINE...
Small Craft Advisory from 2am to 8pm EDT Thursday for ANZ232>234. Small Craft Advisory until 8pm EDT Friday for ANZ235-237. Small Craft Advisory until 8pm EDT Friday for ANZ254>256.