Marine Weather Net

Boston Harbor Marine Forecast


TONIGHT

N
WINDS
15 - 20
KNOTS

TUE

W
WINDS
5 - 10
KNOTS

TUE NIGHT

NW
WINDS
5 - 10
KNOTS

WED

N
WINDS
5 - 10
KNOTS

The Marine Weather Forecast In Detail:
ANZ230 Forecast Issued: 745 PM EST Mon Nov 18 2019

SMALL CRAFT ADVISORY IN EFFECT UNTIL 9 PM EST THIS EVENING
Tonight...N Winds 15 To 20 Kt With Gusts Up To 30 Kt, Becoming Nw 10 To 15 Kt With Gusts Up To 20 Kt After Midnight. Waves Around 2 Ft, Except 5 To 8 Ft At The Outer Harbor Entrance. Patchy Fog. A Chance Of Rain This Evening. Rain Likely After Midnight. Vsby 1 To 3 Nm.
Tue...W Winds 5 To 10 Kt. Waves 1 Foot Or Less, Except 3 To 5 Ft At The Outer Harbor Entrance. Patchy Fog. Rain Likely. Vsby 1 To 3 Nm.
Tue Night...Nw Winds 5 To 10 Kt. Waves 1 Foot Or Less, Except 2 To 4 Ft At The Outer Harbor Entrance.
Wed...N Winds 5 To 10 Kt, Increasing To 10 To 15 Kt With Gusts Up To 20 Kt In The Afternoon. Waves Around 2 Ft. A Chance Of Showers. Vsby 1 To 3 Nm.
Wed Night And Thu...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft.
Thu Night...Sw Winds 5 To 10 Kt. Waves 1 Foot Or Less.
Fri...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft. A Chance Of Showers.
Fri Night And Sat...W Winds 10 To 15 Kt With Gusts Up To 25 Kt. Waves Around 2 Ft.
Sat Night...W Winds 5 To 10 Kt. Waves 1 Foot Or Less. A Chance Of Showers. Vsby 1 To 3 Nm. 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
1022pm EST Monday Nov 18 2019

Synopsis
The coastal storm will continue to bring spotty light rain and strong winds along the coast tonight. The rain may become a wintry mix across the interior high terrain late tonight into Tuesday morning. Mainly dry and seasonably chilly weather follows Tuesday afternoon into early Wednesday. Low pressure passing south of the region may push some rain and snow showers across central and eastern areas from midday Wednesday into Wednesday night. Dry conditions and seasonable temperatures for Thursday. An approaching front will bring a chance for showers on Friday, then dry but colder conditions Friday night into Saturday. Another system may approach Saturday night into Sunday, but the details remain uncertain.

Near Term - Until 6am Tuesday Morning
10 PM

Radar mosaic shows enhanced area of precipitation in the lower Hudson Valley in NY and into NJ/east PA. This is on the nose of stronger 500 mb height falls/mid- level diffluence associated with upper low which per satellite imagery is roughly analyzed over the eastern West Virginia Panhandle. This feature is expected to move N/NEward towards Southern New England overnight with steadier precipitation resuming mainly around/just after midnight in the west, and likely into the overnight/pre-dawn hrs across central/eastern MA-CT and RI.

In the interim, shower coverage has really diminished to either intermittent showers or drizzle especially from eastern CT/central MA eastward. This appears to be due to a dryslot on the eastern extent of the upper low, with better mid-level moisture prevalent over eastern NY into western CT/western MA. Showed rain and drizzle thru first part of the overnight from eastern MA/RI to east- central MA/eastern CT.

00z RAOBS at OKX/ALB showed a prevalent warm nose with maximum warm-nose temps between +3.5C at ALB to +7C at OKX, underlying cool though still above- freezing below-warm nose temps. With cool advection taking some time to erode the warm nose, rain should initially predominate but the potential for northerly drainage flow to advect cooler wet-bulb temps across the higher elevations in the Berks, idea of an expected transition from RA to ice pellets/brief FZRA looks on track before things become a clumpy wet snow into the morning. Winter Weather Advisory still looks valid for light wintry mix leading to some road impact overnight, though will reassess the end timing with the morning package.

Did tweak hourly temps somewhat to account for current observations and near-term trends, though these changes were small.

Previous Discussion... Through the overnight hours, the next round of precipitation approaches. This is associated with a potent mid level trough lifting north out of the Delmarva, ushering out today's coastal low, while bringing another slug of moisture with it. PWATs (Precipitable Waters) >0.75" together with potent mid-level energy and favorable jet dynamics aloft will bring fairly widespread rain showers to all of southern New England generally after midnight into Tuesday morning, with the greatest Quantitative Precipitation Forecast amounts in western MA/CT.

Surface temperatures have been adjusted slightly warmer in line with the latest hi-resolution guidance which has lessened the magnitude of cold air advection, decreasing the risk of appreciable snow/icing overnight. However, in the highest elevations of the Berkshire slopes, temperatures will hover at or near freezing, so can't rule out a coating of snow or light glaze of ice early Tuesday morning. For the possibility of some light freezing rain, a Winter Weather Advisory continues through Tuesday morning for western Hampshire and Franklin counties.

Short Term - 6am Tuesday Morning Through Tuesday Night
Tuesday starts wet before drying out by late morning/afternoon. By 15Z (10AM) the core of the upper low is over Maine, along with the bulk of the moisture. Looking through the column we see some drier air working in in the mid and upper levels which should allow for peeks of sun Tuesday afternoon. This will help warm temperatures a bit too, even in the Cold Air Advection pattern. High temps should reach into the 40s for most, which, with light winds and the emerging sun will be a nice change from today's wet, raw weather. Tuesday night into Wednesday morning things stay dry but we'll see increasing clouds. This as a deep mid level trough digs to our south, eventually wrapping around enough moisture to bring some rain and snow showers on Wednesday. Cold Air Advection pattern will be evident overnight (850mb temps down to -2 to -3C), with surface lows about 5 degrees colder than the night previous, in the upper 20s and low 30s.

Long Term - Wednesday Through Monday
Highlights... * Light rain and/or snow showers push across central and eastern areas Wednesday into Wednesday night as an offshore low passes. Gusty northerly winds develop across the coastal waters.

* High pressure brings dry, seasonable weather on Thursday

* Mild temperatures make a brief return ahead of an approaching front, bringing showers Thu night and Fri, then dry but colder weather late Fri night into Sat

* Model solution spread lending to low confidence forecast for potential approaching system sometime next weekend

Overview... An amplified but progressive mid level steering pattern continues across the lower 48. H5 trough may bring some unsettled conditions around mid week, but should push steadily offshore. Will see a brief dry and seasonal day as progressive H5 ridge pushes across the eastern seaboard. Cutoff H5 low crosses eastern Ontario/Quebec, with a trailing surface front swinging across Fri night into Sat.

Solutions amongst the 12Z model suite signaling increasing spread next weekend. This lends to rather low confidence as another system may approach during this timeframe.

Details... Wednesday and Wednesday night... An amplified long wave trough, with a cutoff H5 low passing close to or S of the region, will lift E-NE Wednesday afternoon into Wednesday night. Looks like moisture will shift back across central and eastern areas during the midday and afternoon hours before moving offshore. May see some light snow showers across N central areas, with mainly rain showers across eastern Mass. Mainly northerly winds in place, but temps will top off in the upper 30s to lower 40s as most of the colder air holds back until the trough shifts E.

Leftover showers linger across the mid and outer Cape Wednesday evening, then will exit rather quickly as drier air moves in on NW winds. Temps will bottom out in the mid-upper 20s well inland to the mid- upper 30s along the immediate coast, which are close to seasonal normals. Will see winds gusts up to 20-25 kt across the outer Cape and Nantucket, as well as across the coastal waters.

Thursday and Thursday Night... H5 ridge will steadily shift E, along with large surface high pressure that will cross the eastern seaboard. NW winds will start off gusty especially along the coast, but will diminish as the ridge builds E. Highs will range through the 40s.

As the ridge shifts offshore Thu night, will see light/variable winds to start then becoming S-SW. This will allow temps to bottom out Thu evening, then will slowly rise through the remainder of the night. Clouds will also increase during the night as the next system approaches. May see scattered showers develop and move across mainly around or after midnight, with the best chances across central and western Mass, possibly into N central CT.

Friday through Sunday
Looks like showers will be scattered across the region through Friday as the front pushes across, though there is some question on the timing of this feature with increasing model solution spread. Ahead of the front, temps will be mild. Expect readings topping off from the mid-upper 40s across the higher inland terrain to the lower- mid 50s across the coastal plain.

A lot of question remain in place for the upcoming weekend weatherwise. Model solutions are spread out, mainly with how each member is handling a potential southern stream system that may try to lift NE. This is likely due to wide spread in the handling of the mid level features, namely how fast the next northern stream system moves along as well as a possible southern stream short wave that may merge with the northern stream system. For now, have started off dry, then could see unsettled conditions. However, quite a bit of uncertainty so low confidence forecast.

Marine
Short Term /through Tuesday Night/...Moderate confidence.
10pm Update:

Made several changes to marine headlines.

Winds have largely subsided below gale criteria (though may briefly ~ next hour be high end SCA/low-end gale on the northeast offshore waters). With continued improvement/easing north/northwest gusts, converted all prior standing gale warnings to small craft advisories. So the biggest change is that gale warnings are no longer in effect.

In the near-shore zones, existing SCAs (Small Craft Advisories) (Boston Harbor and Narragansett Bay) were allowed to expire as winds/seas per obs and trends have fallen below SCA (Small Craft Advisory) levels. However, per the recent BUZM3 ob indicating continued low-end SCA (Small Craft Advisory) gusts, opted to extend the SCA (Small Craft Advisory) through midnight for the Vineyard Haven/Buzzards Bay and RI Sound areas; further extension isn't likely with continued improvement.

General idea is that winds will subside a bit quicker than will the seas, with 10-15 footers into Tuesday for the offshore waters. Steady rains have largely become intermittent and/or drizzle, though visibilies will still be around 2-5 miles with periods of mist/fog and intermittent rain showers into Tuesday morning.

Expect West winds at 5-10 kts on Tuesday. Seas up to 5 to 9 ft, highest on the eastern outer waters early, then slowly subsiding but remaining at or above 5 ft through the day.

W-NW winds at around 10 kt early Tuesday night will shift to N after midnight, with gusts up to around 15 kt. Seas will linger at 5 to 6 ft across the outer waters through most if not the entire night.

Outlook /Wednesday through Saturday/... Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.
Wednesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain showers.
Thursday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Slight chance of rain showers.

Friday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Chance of rain showers.

Friday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of rain showers.

Saturday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas. Slight chance of rain showers.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...Winter Weather Advisory until 6am EST Tuesday for MAZ002-008. RI...None.
MARINE...
Small Craft Advisory until 7am EST Tuesday for ANZ231-232. Small Craft Advisory until midnight EST tonight for ANZ233>235- 237. Small Craft Advisory until 6pm EST Tuesday for ANZ250-254>256. Small Craft Advisory until 5pm EST Tuesday for ANZ251.