Marine Weather Net

Boston Harbor Marine Forecast


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10 - 15


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10 - 15

The Marine Weather Forecast In Detail:
ANZ230 Forecast Issued: 1146 AM EST Fri Nov 15 2019

This Afternoon...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft.
Tonight...W Winds 10 To 15 Kt, Becoming Nw 15 To 20 Kt After Midnight. Gusts Up To 30 Kt. Waves Around 2 Ft.
Sat...N Winds 15 To 20 Kt, Diminishing To 10 To 15 Kt In The Afternoon. Gusts Up To 25 Kt. Waves Around 2 Ft.
Sat Night...Ne Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves 2 To 3 Ft.
Sun...Ne Winds 10 To 15 Kt With Gusts Up To 25 Kt. Waves 2 To 3 Ft, Except 4 To 6 Ft At The Outer Harbor Entrance.
Sun Night...Ne Winds 15 To 20 Kt With Gusts Up To 30 Kt. Waves 2 To 3 Ft, Except 5 To 8 Ft At The Outer Harbor Entrance. A Chance Of Rain.
Mon...N Winds 15 To 20 Kt With Gusts Up To 30 Kt. Waves 2 To 3 Ft, Except 5 To 8 Ft At The Outer Harbor Entrance. Rain Likely.
Mon Night Through Tue Night...Nw Winds 10 To 15 Kt With Gusts Up To 25 Kt. Waves Around 2 Ft, Except 4 To 6 Ft At The Outer Harbor Entrance. A Chance Of 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
1018am EST Fri Nov 15 2019

Milder air moves into the region today ahead of a cold front dropping south from Northern New England. This front will sweep across the region tonight and will be followed by much colder air and gusty north winds into Saturday. High pressure will bring a brief period of dry weather Sunday. A coastal storm will then bring rain and wind, possibly some interior ice Sunday night and Monday. A second storm may impact the region Wednesday followed by high pressure on Thursday.

Near Term - Until 6pm This Evening
10am Update:

Based on continued radar/satellite trends, ended up increasing sky cover and maintaining isolated showers toward Cape Cod and the Islands and adjacent southern waters for another couple hrs. Used an equal-parts blend of the 00z HREF and a consensus of shorter-range high res guidance to reflect this - not really anticipating showers to be enough to measure but did want to carry a continued mention of isolated showers going through the morning. Improvement appears more likely into the early-afternoon hrs.

However for the rest of Southern New England, it's an otherwise uneventful late-morning with plenty of sun and southerly flow resulting in current temps mainly in the upper 30s to mid 40s. Sunny skies expected to continue through the day, and continued warming should push highs to maxes in the upper 40s to mid 50s. Will see some southerly gusts develop to around 20 mph into the afternoon. We'll be headed back into unseasonably cold air tomorrow, so hopefully you'll have an opportunity to enjoy today's seasonable temperatures.

Previous discussion follows... Axis of scattered showers early this morning from the NJ coast to vicinity of Nantucket along a weak boundary. This boundary will keep clouds and a low risk of a shower over Nantucket this morning before clearing this afternoon. Otherwise, mostly sunny skies across SNE as the column remains rather dry. But some increase in cloud cover over northern and western MA later in the day as low level moisture increases. Modest W/SW flow ahead of arctic front dropping south into northern New Eng will bring milder air into the region with high temps reaching mid 40s to lower 50s, which is near seasonable for this time of year. SW winds may occasionally gust to 20 mph.

Short Term - 6pm This Evening Through 6pm Saturday
Tonight... Arctic front moves north to south across SNE around 03-06z, perhaps an hour or 2 later along the immediate south coast and Islands. Moisture and convergence are limited given westerly flow ahead of the front so not expecting much more than a band of sct-bkn clouds with the front. Much colder airmass advects into the region late tonight on gusty N winds. Gusts to 25-35 mph expected, strongest along the coast. Low temps will settle into upper teens to mid 20s by daybreak except closer to 30 over the outer Cape/Islands. Wind chills bottom out in the single numbers and teens late tonight and Sat morning.

Saturday... High pressure builds across southern Quebec with winds gradually diminishing in the afternoon. But a period of 30-40 mph wind gusts possible along the coast in the morning. Very dry airmass in place with PWATs (Precipitable Waters) less than 0.1", about as dry as it gets. We will have full sunshine but unseasonably cold temps. Highs mostly in the mid 30s, closer to 30 over higher elevations, but the gusty N winds will make it feel considerably colder.

Long Term - Saturday Night Through Thursday
00z guidance still showing next week will feature an active weather pattern, with the headliner being a coastal low/nor'easter that will move up the east coast to start the work week. As is always the case this far out, there are model differences, some of which lead to fairly significant differences to the weather that we would experience. For the most part, continued with a model blend, though leaned a little more toward the 00z ECMWF (European Centre for Medium-Range Weather Forecasts) with regard to precipitation timing Sunday night -- which had the net effect to slow things down about 6-8 hours from the straight blended approach. The potential for some interior freezing rain and light ice accumulation Sunday night still remains. In addition, latest storm surge guidance indicates the potential for very minor coastal flooding with Monday afternoon high tide. For those AFD readers out there who want more 3am-ish ramblings, continue on for the daily details... Saturday Night: Another cold, clear, dry night. With dewpoints in the single digits (especially inland) and winds diminishing (especially inland), lows will bottom out in the 15-20F range (especially inland). Winds along the east coast and Cape and Islands will keep going all night as they start to turn more NE. This will keep it marginally warmer in those areas with 20s to lower 30s.

Sunday: Coastal low will be in full swing off the Carolinas coast. Low level easterly flow will get established across the region, and be a little gusty along the east coast, Cape and Islands. Expecting mainly high clouds to increase during the day. Highs will moderate some from Saturday, but still below normal with mid/upper 30s interior to low/mid 40s eastern coastal sections. Still much uncertainty in timing of precipitation. 00z NAM brings precipitation northward during the afternoon. This model is most aggressive, and given the dry airmass that will be in place, don't see that happening. Liked the depiction the 00z ECMWF has, so used that to drive the hourly PoPs. GFS was slower, and appears to be a little too dry. Net result is to slow the precipitation a few hours from our previous forecast. Light rain should spread to Nantucket late in the afternoon and slowly move north and west. By late Sunday evening it should be to a Boston-Hartford line.

Sunday Night: Here's where things get very tricky. Across interior areas (central/western MA and northern CT) where high temperatures were only in the 30s, by the time the precipitation has made it into this region, they will likely be in the 28-32F range (helped by wet- bulb cooling effects). Forecast temperature profiles aloft show both a lack of moisture in a snow growth region and warming temperatures a few thousand feet above ground which scream to me that liquid will be falling from the sky. Thus it's all about the temperature at the surface. The blend I used gives me cold enough temperatures that the rain will freeze upon contact. However just a few degrees warmer changes everything. Pretty confident future model runs will help zero in on the truth. At this point it doesn't appear that we are looking at heavy rainfall during the period of time icing could occur. I ended up with maximum values of 1/10" of ice. If that is what happens, it will be slow going for travel Monday morning, but that's about all.

Monday: The nor'easter will start to accelerate as it passes by just to the south of the 40N/70W benchmark as it feels the influence of an approaching upper level trough. Certainly a raw day, with steady rain and gusty easterly winds. Not a very intense low, but enough that we should see max gusts over 35mph across SE Mass and the Cape and Islands. However, the fetch area of easterly winds is pretty sizeable, so that should generate a storm surge on the order of 1.5ft. When adding that to the Monday afternoon high tide, we will be very close to the levels where we see minor coastal flooding. At the very least, some splashover is expected. Again, stay tuned for later forecasts as we fine tune that aspect. Storm pulls away Monday night, but as it does so, we will still have moisture around and some cooler air coming in on northwest winds. So the rain may end as a brief period of very light wintry mix across the higher elevations of central/western MA.

Tuesday: Should be generally dry, though clouds will remain as an upper level shortwave zips overhead. Temperatures a little below normal and mostly in the 40s.

Wednesday: GFS and ECMWF both indicate an upper level low will drift across the region. So can't rule out another day with lots of clouds and a few showers. Cold enough aloft (about -4C at 850mb) that this would result in snow showers across the high terrain. Temperatures again mainly in the 40s.

Thursday: looks like we get to see some sunshine as a shortwave ridge moves over. However another fairly robust upper trough and surface low will be off to our west (or say the 00z models). Could be the low is reaching us on Thursday instead. In that case, no sunshine. Later forecasts will work on those details.

10am Update:

Short Term /through Saturday/...High confidence.

Isolated showers to continue across the southern offshore waters into Nantucket Sound until about noon but unlikely to result in restrictions to visibility. Otherwise, SW wind gusts 20-25 kt today will shift to NW this evening to N overnight into Sat behind an arctic front. Gale force gusts to 35 kt developing after midnight and persisting into Sat morning before gradually diminishing. Gale warnings are in effect except SCA (Small Craft Advisory) for Boston Harbor and Narragansett Bay. Seas over the eastern waters will peak around 8-9 ft late tonight and early Sat then slowly subside. Good vsbys.

Outlook /Saturday Night through Tuesday/... Saturday Night: Moderate risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 10 ft.

Sunday: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 13 ft. Slight chance of rain.

Sunday Night: Low risk for gale force winds with gusts up to 35 kt. Rough seas up to 16 ft. Rain likely.

Monday: Strong winds with gusts up to 35 kt. Rough seas up to 16 ft. Rain likely.

Monday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 15 ft. Chance of rain.

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

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
Gale Warning from 3am to 1pm EST Saturday for ANZ232>235-237. Small Craft Advisory from 10pm this evening to 1pm EST Saturday for ANZ230. Gale Warning from 1am to 1pm EST Saturday for ANZ231-250-251- 254>256. Small Craft Advisory from 1am to 5pm EST Saturday for ANZ236.