Marine Weather Net

Cape Cod Bay Marine Forecast




5 - 10


5 - 10



The Marine Weather Forecast In Detail:
ANZ231 Forecast Issued: 101 PM EST Thu Dec 07 2023

This Afternoon...Nw Winds Around 10 Kt. Seas Around 2 Ft.
Tonight...Nw Winds 5 To 10 Kt. Seas Around 2 Ft.
Fri...Nw Winds 5 To 10 Kt, Becoming W In The Afternoon. Seas Around 2 Ft.
Fri Night...S Winds Around 5 Kt. Seas 1 Foot Or Less.
Sat And Sat Night...S Winds 5 To 10 Kt. Seas 1 Foot Or Less.
Sun...S Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 2 To 3 Ft. A Chance Of Showers.
Sun Night And Mon...S Winds 25 To 30 Kt, Becoming Sw. Gusts Up To 45 Kt. Seas 4 To 7 Ft. Showers. Vsby 1 To 3 Nm.
Mon Night...W Winds 15 To 20 Kt With Gusts Up To 35 Kt. Seas 4 To 6 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
253pm EST Thu Dec 7 2023

High pressure maintains dry weather through Saturday with temperatures rising to above normal levels. A strong frontal system has the potential to bring a period of heavy rain, strong southerly winds and coastal flooding along the south coast late Sunday into early Monday. Turning drier by Monday afternoon with a brief shot of colder air for Monday night, but temperatures look to rebound back closer to seasonable levels by next Tuesday and Wednesday.

Near Term - Until 6pm This Evening
Mid level shortwave and jet max will be moving east of New England tonight followed by rising heights. At the surface, high pressure ridge will be in control with a dry airmass and light to calm winds. Lots of mid/high clouds across SNE this afternoon with leading edge of lower clouds and a few snow showers in eastern NY. This in response to weak low level warm advection ahead of warm front in central NY. The low levels are rather dry so most of the snow showers will erode as they approach the Berkshires with just a few flurries possible here through the afternoon. Otherwise, expect clearing skies this evening across much of SNE as mid/high level moisture moves out. Exception will be across western MA/CT where some lower clouds may spill in from the west. Expect decent radiational cooling further E with clearing skies and light to calm winds so we leaned toward colder MOS guidance for temps. Lows will drop into the teens in colder spots in northern and interior eastern MA, with 20s elsewhere.

Short Term - 6pm This Evening Through 6pm Friday
Friday into Friday night... Mid level ridge builds east into New England while surface ridge over New England slowly shifts to the east Fri night. Some lower clouds may linger into Fri morning in the west, otherwise, mostly sunny skies with moderating temps as low levels warm. Highs should reach upper 30s to lower 40s with light winds. Continued dry Fri night as the high pressure gradually moves to the east. Clouds will be increasing overnight in the developing weak warm advection with the potential for some lower clouds developing. Decent radiational cooling in the evening before clouds increase should allow temps to fall into the 20s in the typically colder locations with 30s near the coast. Temps leveling off overnight.

Long Term - Friday Night Through Thursday
Key Points... * Quiet, dry, and milder on Saturday and the first half of Sunday.

* A strong storm system will bring widespread rain, strong (potentially damaging) winds, and the possibility of coastal flooding on the south coast.

* Quiet and colder Tuesday through Thursday

The first half of the weekend will be quite nice for outdoor activities as SNE is placed beneath a sprawling surface high pressure and mid level ridge providing subsidence and dry, increasingly mild weather on warm SW flow. While normal high temperatures for early December are in the low to mid 40s, afternoon highs will reach the upper 40s for west/central MA and the mid 50s for southeast MA/RI. We'll then see a very deep trough cross the region bringing unsettled weather to the region Sunday into Monday which will be discussed in further detail below. Beyond that more zonal mid level flow moves in with broad surface high pressure at the surface for Tuesday into at least Wednesday leading to dry, quiet, and colder weather for mid week as highs settle back in the 40s.

The main focus in the extended forecast period is the late Sunday into Monday period as a strong frontal system and neutral to slightly negatively tilted trough move out of the Ohio Valley and cross New England Sunday night. The anomalous nature of several parameters including moisture (PWAT) and wind spell potential for a concerning event on a few fronts.

As for the rainfall potential, this system has abundant moisture with PWATs (Precipitable Waters) exceeding 3 standard deviations from normal for December. This, combined with the very strong dynamics (a low level jet ranging from 50 kts to as much as 80+kts over the outer Cape) will yield rainfall amounts from 1 to 2+ inches between Sunday and Monday afternoon. The highest amounts will be over the interior (western MA/CT) where forcing will be enhanced by orographics as well as from the slightly negatively tilt of the mid level trough and divergence aloft thanks to placement beneath the right rear quadrant of a 145 kt low level jet. This is also where there is a tight gradient from core of the LLJ to the slower winds to the north which will enhance low level convergence. Ensembles depict a 20-30% chance of seeing 3+ inches of rain here. Further east we may see localized maxima thanks to some elevated instability in the warm sector leading to scattered convection. The progressive nature of the system will help keep flooding issues from being a big concern (save for urban/poor drainage flooding) but some rises on rivers are expected, and the MMEFS depicts a 30% chance of minor flooding at points on the CT River; something to watch.

As for winds, given the aforementioned anomalous low level jet and expected temperature inversion near the surface over southeast MA it will be a matter of just how much of that wind can mix down to the surface. One thing that could help mix down the stronger gusts would be any convective elements that may develop. To be sure, it will be windy regardless, but as for the 45+ mph potential that will be confined primarily to RI and southeast MA. Ensemble guidance depicts a 50-80% chance of 45+ mph gusts over this region; generally thinking 45-60 mph gusts are the best bet right now but things will change as we get into the higher resolution guidance.

Finally, the peak of the southerly winds looks to be during the early morning hours of Monday. Even though places like Narragansett Bay won't have an astronomically high tide at the time, if the peak of the wind/surge coincides with high tide (6:20am in Providence) it could spell some coastal flooding is possible. It will all come down to exact timing which we won't be able to nail down until much closer to the event.

Forecaster Confidence Levels:

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

High Confidence.

Expecting winds and seas to diminish early this morning as high pressure moves overhead through tonight, then offshore Friday. Thinking Small Craft Advisories may be able to be let go earlier than current timing. Otherwise, light winds and seas expected across the waters through Friday.

Outlook /Friday Night through Tuesday/... Friday Night through Saturday Night: Winds less than 25 kt.

Sunday: Low risk for gale force winds with gusts up to 35 kt. Seas locally approaching 5 ft. Chance of rain. Local visibility 1 to 3 nm.

Sunday Night: Low risk for storm force winds with gusts up to 50 kt. Rough seas up to 14 ft. Rain, isolated thunderstorms, patchy fog. Visibility 1 to 3 nm.

Monday: Low risk for storm force winds with gusts up to 50 kt. Rough seas up to 15 ft. Rain, patchy fog. Areas of visibility 1 to 3 nm.

Monday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 13 ft.

Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.