Marine Weather Net

Boston Harbor Marine Forecast


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The Marine Weather Forecast In Detail:
ANZ230 Forecast Issued: 1034 AM EDT Sun Sep 22 2019

This Afternoon...Sw Winds 5 To 10 Kt. Waves 1 Foot Or Less.
Tonight...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft.
Mon...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft.
Mon Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt, Diminishing To 5 To 10 Kt After Midnight. Waves Around 2 Ft In The Evening, Then 1 Foot Or Less. Showers Likely.
Tue...W Winds 5 To 10 Kt. Waves 1 Foot Or Less. A Chance Of Showers In The Morning.
Tue Night...Nw Winds 5 To 10 Kt. Waves 1 Foot Or Less.
Wed...W Winds 5 To 10 Kt. Waves 1 Foot Or Less.
Wed Night...Sw Winds 5 To 10 Kt. Waves 1 Foot Or Less.
Thu...Sw Winds 5 To 10 Kt. Waves 1 Foot Or Less, Then Around 2 Ft In The Afternoon.
Thu Night...Nw Winds 5 To 10 Kt. Waves Around 2 Ft In The Evening, Then 1 Foot Or Less. 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
1007am EDT Sunday September 22 2019

High pressure remains in control into Monday with summer-like temperatures and dry weather. Showers likely Monday night along a sweeping cold front. High pressure settles in through midweek with mild days and cool nights.

Near Term - Until 7pm This Evening
10 AM

Fog continues to burn off along the south coast of MA and RI with fog now completely eroded across Cape Cod and Buzzards Bay. RI coastline will take longer into northeast CT but should be eroded by noon with increasing sun angle and boundary layer mixing.

Otherwise another fabulous summer-like day in late September. Already 76 degs at Norwood! Yesterday 925 mb temps were about +19C and that translated to highs of 80-85. Today we have +19C over southern New England per latest Storm Prediction Center mesoanalysis but +21C over NY/PA will advect across the region this afternoon. This should support highs in the mid to upper 80s away from the south coast with cooling SSW winds off the ocean. Could even see a few communities in northeast MA including Boston briefly touch 90 this afternoon. Thus have sided with the warmest guidance.

ESE swells have diminished to 2-3 ft with a period of every 10 seconds. Thus surf will not be as rough as yesterday.

.SHORT TERM /7pm THIS EVENING THROUGH 6pm MONDAY/... SW winds should help to maintain above normal temperatures through Monday. Humidity will be increasing, too. Looking at patchy fog once more tonight into early Monday morning.

A mid level cutoff moves over the Great Lakes by late in the day. This should produce an increase in clouds, and a risk for showers late in the afternoon across western MA. Decent instability parameters, so cannot dismiss the possibility of a few thunderstorms ahead of a cold front. Locally heavy rainfall will be possible in any thunderstorms.

Expecting increasing swell from the south Monday, this time from Tropical Storm Jerry. This should lead to another period with an elevated risk for dangerous rip currents, mainly along south- facing, ocean-exposed portions of the coast.

Long Term - Monday Night Through Saturday
*/ Highlights... - Showers likely Monday night - Warm-up and dry through midweek - Another sweeping cold front around Thursday night - Low confidence forecast into the following weekend

*/ Overview... Tropics are active. Multiple cast members supported by a phase 1 MJO crew. As members are drawn into the mid-latitude production they in part bring chaos to the show. From the NW Pacific to the NW Atlantic S equatorward, the multitude of systems, accumulated cyclone energy, latent heat release, all of which has the opportunity to be drawn N as the pattern slows and buckles, the subsequent result of warm air advection across Alaska and further downstream over Greenland that yields subsequent blocks. A CONUS trough.ridge, near climatological- record percentiles by the weekend, the NE-CONUS in the NE-periphery of the MS/OH Valley ridge with a +1-2 standard deviation temperature anomaly through the column, by weeks-end into the following weekend it'll be interesting as to the heat and humidity magnitude that'll be able to advect into the NE-CONUS beneath prevailing NW-flow aloft likely prior to SE-sweeping cold fronts. Rainfall opportunities that ensemble-means continue to show synoptically remain uncertain as to outcomes as well as how warm it potentially could get. Any nudge in the ensemble mean longwave pattern could put us either in a warm-dry pattern or a mild-wet setup. Nevertheless temperatures look to be above-average into early October as emphasized by CPC forecasts, but lower confidence with respect to precipitation outlooks. Dependence on the longwave pattern breakdown. Aside we really need some rain.

For now through the early half of the week, +WPO/+EPO signals with a robust N Pacific jet into the CONUS, energy cascades E. Grasping at continental-moist airmasses, there's opportunity for some rainfall Monday night and again Thursday night (however the latter becoming weighed down by increasing heigheights as the pattern begins to buckle). Mild days and cool nights. Break down details below.

*/ Discussion... Monday night... Showers likely. Cold frontal lift, convergent low-level winds, all beneath a neutral-tilt trough with attendant vortmax, cyclonic flow, and jet dynamics, certainly forcing will act upon a continental- moist airmass with precipitable waters close to 2-inches. Narrow ribbon of moist-adiabatic, conditionally-unstable profile with some decent W shear, can't rule out some heavy downpours, maybe a rumble of thunder. Forecast guidance has been all over the place with rain- fall. But given synoptics would think something will squeeze out. Deep-layer moisture with the aforementioned ribbon well up to H5-3 and warm-cloud bases up to 14 kft, some areas could see that 0.50 if not more. Just a challenge to where exactly but there's indication of deep-layer lift will occur somewhere. Likely PoPs. Mild.

Tuesday into Wednesday... Clouds lingering. Light showers N beneath the closed mid-upper level low slowly working E. Downsloping W/NW flow. Gradual clearing, mild days, cool nights. Above-average temperatures when normally for late September we should see highs around 70, lows around 50. Expect it to be around +5 degrees with respect to the two.

Thursday into Thursday night... Sweeping cold front and a chance of showers. However heigheights on the rise as the longwave pattern buckles, a trough digs over the W CONUS with the ridge building E. Rainfall outcomes could be suppressed prior to ending up on our doorstep. Remaining mild.

Friday onward... Low confidence forecast depending on the longwave CONUS setup. We could end up warm and dry, or rather mild with on and off rainfall chances along sweeping cold fronts.

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

Short Term /through Monday/...High confidence.

10am update ... Only issue this morning is lingering dense fog along the RI coastline and another fog bank east of Cape Cod. Both areas continue to slowly erode and should have visibilities to the horizon by midday. Earlier discussion below.


Light winds this morning, becoming S-SW winds and increasing to 15-20 kt this afternoon and evening with gusts up to 25 kt possible toward sunrise Monday. Patchy fog and low clouds may limit vsby this afternoon through through tonight. Dry weather prevails. Seas build across the outer coastal waters. Small Craft Advisories posted for late tonight into Monday.

Outlook /Monday Night through Thursday/...Moderate confidence.
Monday Night: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Chance of rain showers, slight chance of thunderstorms.

Tuesday: Winds less than 25 kt. Local rough seas. Slight chance of rain showers.
Tuesday Night: Winds less than 25 kt. Local rough seas.

Wednesday through Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.
Thursday: Winds less than 25 kt. Seas up to 5 ft.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
Small Craft Advisory from 1am to 8pm EDT Monday for ANZ232>235-250-254>256. Small Craft Advisory from 6am to 8pm EDT Monday for ANZ231- 237.