Marine Weather Net

Cape Cod Bay Marine Forecast


10 - 15


10 - 15


5 - 10


5 - 10

The Marine Weather Forecast In Detail:
ANZ231 Forecast Issued: 416 AM EST Sat Feb 22 2020

Today...W Winds 15 To 20 Kt, Becoming Sw 10 To 15 Kt This Afternoon. Gusts Up To 25 Kt. Seas 2 To 4 Ft.
Tonight...W Winds 10 To 15 Kt, Diminishing To 5 To 10 Kt After Midnight. Gusts Up To 20 Kt. Seas Around 2 Ft.
Sun...Sw Winds 5 To 10 Kt. Seas Around 2 Ft.
Sun Night...Sw Winds 5 To 10 Kt. Seas Around 2 Ft.
Mon...Sw Winds 5 To 10 Kt. Seas Around 2 Ft.
Mon Night...Sw Winds 5 To 10 Kt. Seas Around 2 Ft.
Tue And Tue Night...Ne Winds 5 To 10 Kt, Increasing To 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 3 Ft. A Chance Of Rain.
Wed...E Winds 10 To 15 Kt With Gusts Up To 25 Kt. Seas 2 To 4 Ft. Rain Likely.
Wed Night...E Winds 15 To 20 Kt With Gusts Up To 30 Kt. Seas 3 To 5 Ft. Rain. 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
443am EST Sat Feb 22 2020

High pressure will bring an extended period of dry and relatively mild afternoon temperatures today, and especially Sunday and Monday. Our weather pattern then turns increasingly more active Tuesday through Thursday. A warm front may produce a wintry mix across northern interior locations to rain elsewhere for Tuesday night into Wednesday. Another stronger low pressure area and strong cold front then affect the region Wednesday night into Thursday. Pattern change towards colder weather for late in the week.

Near Term - Until 6pm This Evening
350 AM

A ridge of high pressure to our south will generate a milder westerly flow of air into the region today. After a chilly start, sunny skies and 925T near -3C will allow for a nice recovery with good mixing. Afternoon highs should rebound into the lower 40s in the higher elevations, to the middle to upper 40s elsewhere. Westerly wind gusts of 20 to 25 mph will develop later this morning and afternoon. Overall, a great start to the weekend for late February standards.

Short Term - 6pm This Evening Through 6pm Sunday
Tonight... A ridge of high pressure will remain anchored to our south. Mainly clear skies and diminishing winds with the loss of daytime heating will allow for overnight lows to bottom out in the 20s in most locations.

Sunday... A beautiful day to close out the weekend. High pressure remains to our south and height fields rise a bit from today. This coupled with a milder start will allow for a very mild afternoon. Plenty of sunshine should allow Sunday afternoon high to reach the lower to middle 50s in many locations. These readings are close to 15 degrees above normal for late February.

Long Term - Sunday Night Through Friday
Highlights... * Dry weather with mild temperatures into Monday. Potential for some spots to reach 60 degrees on Monday before mid-layer clouds come in.

* Increasingly unsettled weather pattern for Tuesday into Thursday. Interior wintry mix near or north of the Mass Pike Tues nite into early Wednesday (possible Advisories?), with rain elsewhere. A larger rain maker associated with secondary surface low and a sharp cold front then for Wednesday nite - Thurs.

* Building E/NE winds and building seas on the waters Wednesday into Thursday.

* Pattern change toward below-avg temps and blustery NW winds Thursday nite into Friday.

Details... Sunday Night through Monday Night:

Sunday night continues to look uneventful weather-wise amid quasi- zonal mid-level flow and surface warm sector air mass in place. Monday may prove even warmer than Sunday, with potential for highs to again overachive compared to the preponderance of guidance. Looking at continued southwest breezes, the increasing late-Feb sun angle allowing for somewhat deeper mixing, and 925 mb temps in the +4 to +6C range. Have opted to incorporate more of the milder ECMWF (European Centre for Medium-Range Weather Forecasts) and NAM MOS into the forecast versus colder NBM guidance, and this brings highs in the 50s for most locales. It's not out of the question that a few sites in the interior/coastal plain may take a run at 60 degrees, though increasing mid to high clouds late in the day could keep highs just cooler than that.

For Monday nite, the 00z/22nd NWP (Numerical Weather Prediction) suite starts to show some subtle but nonetheless important changes from earlier continuity. A potent northern-stream trough near Hudson Bay and its related surface frontal system looks to progress eastward through Quebec late Monday into Monday nite. Passage of this system should impart weak subsidence/ridging ahead of the deamplifying lead southern-stream trough and surface cyclone progressing ENE from the Ohio Valley. This latter feature had looked to spread some light rain showers into our area, but given both the subsidence/weak shortwave ridging in place and model soundings indicating dry sub-cloud air/inverted-V profiles. I've opted to reduce Probability of Precipitation Monday nite at no better than slight chance; if anything were to fall it would be quite light and/or be virga. The other change was to show cooler temps into northern/NW MA, given northerly surface flow associated with the passage of the northern- stream frontal system's cold front. Kept lows in the 30s areawide, mid/upper 30s mainly near and SE of the Mass Pike, though may be close to freezing across part of the Merrmack Valley, northern Worcester Hills into the Pioneer Valley/east slopes of the Berks.


Significant change to the 500 mb height pattern across the central/east-central CONUS then looks to evolve on Tuesday. A pronounced trough/closed low looks to set up over much of the northern-central Plains into the Great Lakes/Ohio Valley. The effects of this trough will mainly affect our area late Tues continuing into Thurs, but Tues nonetheless will begin a more active weather pattern.

Weak CAD profile with light NE/E flow looks to prevail on Tuesday, and while a warm front projects to lie just south of Southern New England any related showers falling on the cool side of the boundary project to be rather light. Nevertheless, turning more unsettled with overcast skies and spotty light showers (Quantitative Precipitation Forecast amounts less than a tenth of an inch). Highs mainly in the 40s.

Tuesday Night into Thursday:

Most active period in the upcoming workweek looks to be in this rather broad time window. This occurs as the aforementioned 500 mb trough progresses eastward from the Ohio Valley, then assuming a negative tilt Wednesday nite into Thurs.

Surface ridge/CAD wedge profile over NH/northern MA, with E/NE winds is maintained Tues nite into Wed. This occurs as lead southern- stream mid-level trough deamplifies and spreads warm-frontal precipitation northward across most of Southern New England. The big question is on 2-m AGL temps/wet-bulb temps given the NEly trajectories. While mostly rain from the Mass Pike south, cooler NE CAD conditions in northern MA may offer a period of wet snow to wintry mix (PL/FZRA?) Tues nite into early Wednesday across at least NE through NW MA. This light wintry weather potential may extend as far south as the Worcester-Springfield-Windsor Locks area. Depending on these 2-m temps, could see a need for winter weather advisories with minor travel impact for the Wedam commute not out of the realm of possibility in parts of this area. Something to consider as we get into the range of the mesoscale models. Slow S to N non-diurnal moderation to temperatures is expected into Wed, with any leftover wintry precipitation becoming confined to the higher elevations by Wednesday afternoon. Will indicate lows 30-32F N/W of the Mass Pike into the Route- 2 corridor, mid-30s from the North Shore through northern Hartford County, and mid-upper 30s Hartford area through the I-95 corridor on into SE MA/RI and the Cape. Highs only expected to rise a couple degrees from these lows given the cooler E/NE flow.

Bigger precip-maker then looks to arrive Wednesday night into Thurs. Surface ridge/CAD weakens quickly Wednesday nite, as a broad warm sector on SSW low-level flow advects out ahead of the secondary cyclone over the north-central Appalachians/Blue Ridge Mtns. 850 mb temps surge to between +6 to +9C Wednesday nite, with rising PWAT (Precipitable Water) values to around 0.75" to near 1". With the increase in PWAT (Precipitable Water) values to these levels and given good multi-model consistency on precipitation chances, have opted to raise Probability of Precipitation to solid Likely to Categorical levels for mainly rain Wednesday nite into mid-day Thurs ahead of the secondary surface low and the sharp cold front. While rain chances are greatest for the first part of Thurs, a rapid decrease in Probability of Precipitation expected behind the cold front for Thurs afternoon with strong cold advection resulting in increasing W winds and falling surface temps.

Another consideration will be marine winds/seas and the potential for coastal flooding, mainly Wednesday into Thurs. Surface high over ME looks to maintain NE/E winds across two tidal cycles. In fact will increase a bit into Wednesday nite/Thurs with 925 mb jet of 50-55 kt projected to shift northward across the waters. Will likely need to consider Gale Watches at least the eastern waters in this period with building, increasingly rough seas. Coastal flood threat for the eastern coastal sites however looks quite marginal as astro tides will be steadily decreasing, and it may take a 2-ft or greater storm surge to start to cause problems given astro tides of 9.5-10 ft. Minor splashover could be possible Wednesday nite-Thurs in light of the sustained period of E/NE flow, but even that would seem to be a worst-case outcome.

Thursday Night into Friday:

Pattern change toward colder weather as large mid-level cyclonic gyre sets up just north of Montreal, with broad troughing across most of the Northeast into the mid-Atlantic/Great Lakes and central Appalachian region.

Colder than normal temperatures with blustery conditions on NWly gradient winds looks to settle across our area to close out the workweek. Will have to watch for possible black ice Thurs night as temperatures fall sharply (850 mb temps -10 to -14C by 12z Fri). Highs on Friday may only reach the mid 20s to lower 30s in the interior, and closer to the mid to upper 30s towards the coasts.

Today...High confidence. High pressure to the south of our waters will generate enough westerly flow for WSW 25 knot wind gusts, especially later this morning and afternoon. Small craft headlines are posted for all open waters.

Tonight and Sunday...High confidence. Gradient weakens a bit, so expect WSW gusts to generally remain in the 15 to 20 knot range tonight and Sunday. We still will need to continue small craft headlines for left over 5 foot seas across the southern waters this evening. However, winds/seas should be below thresholds the the rest of this period across all our waters.

Outlook /Sunday Night through Wednesday/... Sunday Night: Winds less than 25 kt. Seas locally approaching 5 ft.
Monday through Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Slight chance of rain.

Tuesday Night: Winds less than 25 kt. Local rough seas. Chance of rain.

Wednesday: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Areas of rough seas. Chance of rain.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
Small Craft Advisory until 9pm EST this evening for ANZ232>235-237. Small Craft Advisory until 4pm EST this afternoon for ANZ231- 250-251. Small Craft Advisory until 5am EST Sunday for ANZ254>256.