Marine Weather Net

Boston Harbor Marine Forecast


TONIGHT

S
WINDS
10 - 15
KNOTS

WED

S
WINDS
20 - 25
KNOTS

WED NIGHT

SW
WINDS
25
KNOTS

THU

W
WINDS
25 - 30
KNOTS

The Marine Weather Forecast In Detail:
ANZ230 Forecast Issued: 401 PM EST Tue Feb 27 2024

GALE WARNING IN EFFECT FROM WEDNESDAY MORNING THROUGH THURSDAY EVENING
Tonight...S Winds 10 To 15 Kt With Gusts Up To 20 Kt, Increasing To 15 To 20 Kt With Gusts Up To 30 Kt After Midnight. Waves Around 2 Ft. Patchy Fog. Showers. Vsby 1 To 3 Nm After Midnight.
Wed...S Winds 20 To 25 Kt With Gusts Up To 40 Kt. Waves Around 2 Ft, Except 3 To 5 Ft At The Outer Harbor Entrance. Patchy Fog. Showers. Vsby 1 To 3 Nm.
Wed Night...Sw Winds Around 25 Kt, Becoming W After Midnight. Gusts Up To 45 Kt. Waves Around 2 Ft, Except 3 To 5 Ft At The Outer Harbor Entrance. Showers, Mainly In The Evening. Patchy Fog In The Evening With Vsby 1 To 3 Nm.
Thu...W Winds 25 To 30 Kt With Gusts Up To 35 Kt. Waves Around 2 Ft, Except 3 To 5 Ft At The Outer Harbor Entrance.
Thu Night...W Winds 25 To 30 Kt, Diminishing To 20 To 25 Kt After Midnight. Waves Around 2 Ft.
Fri And Fri Night...Sw Winds 20 To 25 Kt. Waves Around 2 Ft.
Sat Through Sun Night...Ne Winds 5 To 10 Kt With Gusts Up To 20 Kt. Waves Around 2 Ft. 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
351pm EST Tuesday Feb 27 2024

Synopsis
A strong cold front approaching from the west will bring soaking rains and strong wind gusts to southern New England tonight into Wednesday evening, followed by sharply falling temperatures later Wednesday night. Dry Thursday but windy and colder than normal, then temperatures moderate and less wind Friday. Mild for the weekend into early next week, but also wet at times.

Near Term - Until 6am Wednesday Morning
A fast moving mid level shortwave and accompanying deep moisture plume will move across SNE this evening bringing a period of showers to SNE. These showers are currently moving through western NY and central PA and will arrive 7-9 pm in western New England and by 10 pm in eastern New Eng. There is some convection and lightning to the west with these showers but not much instability in SNE as these showers move through so not expecting any thunder, but there could be some locally heavy downpours with surging PWATs (Precipitable Waters) and some decrease in static stability. Best chance for locally heavy showers will be across RI and SE MA within the axis of the strengthening low level jet. After the shortwave exits around midnight, there will likely be a lull in the precipitation in the interior, but showers will be more persistent across SE New England through the night. Winds begin to ramp up tonight as the low level jet strengthens with gusts increasing to 35-45 mph along the south coast late tonight, with 20-30 mph gusts further in the interior. Mild night with temps holding in the mid- upper 40s, but rising into lower 50s in eastern MA.

Short Term - 6am Wednesday Morning Through Wednesday Night
Key Points... * Strong to damaging wind gusts developing near the coast Wed, then expanding across rest of SNE Wednesday night as winds shift to west

* Locally heavy rainfall near the south coast

* Sharply falling temps Wednesday night with rain possibly changing to a brief period of snow before ending. Minor accum possible over the higher elevations

Wednesday into Wednesday night... Rather dynamic mid level trough approaches from the west and sweeps across New England Wednesday night, with a strong cold front quickly moving though the region 8 pm to midnight. PWAT (Precipitable Water) and low level wind anomalies are 3-4SD above normal which is a good signal for heavy rainfall and strong wind. Will break it down below.

Heavy rainfall... Expect periods of showers Wednesday into Wednesday evening as anomalous PWAT (Precipitable Water) plume lifts north into SNE with low level jet and favorable upper level jet dynamics providing deep layer lift. Not expecting continuous rainfall for entire period but there will be waves of showers right through Wednesday evening until the frontal passage. Instability is limited so thunder probs are low but strong forcing and SWI near zero supports locally heavy convective showers. Hi-res guidance supports some sort of fine line moving in from the west along the front, but it is weakening as it moves into the region. Best chance for locally heavy rainfall will be along the south coast along the nose of the low level jet. This is where locally 2-3 inches of rain is possible, including what falls tonight. Elsewhere, expect 0.50" to 1.50" rainfall. River flooding is not anticipated, but minor street flooding in urban and poor drainage areas is possible where rainfall exceeds 2 inches. However, impacts should not be significant.

Strong wind... Complex wind forecast for Wednesday into Wednesday night as 2 periods of strong to potentially damaging wind are expected. One near the coast with the southerly winds during Wed-Wednesday evening and a second surge with the wind shift to west after the cold front passage. The threat for damaging post frontal winds is greatest over the higher elevations of northern MA.

As is typically the case with these southerly wind events there is a low level inversion which complicates the forecast. Always a challenge to determine how much wind will mix down. Pressure falls are not particularly impressive but we have a strengthening low level jet through the day, peaking at 80-90 kt Wednesday evening over the Cape/Islands per the hi-res model suite. With temps getting into the low-mid 50s this should allow 50-60 percent of the LLJ mixing down which supports 45-55 mph gusts near the coast, and up 60+ mph on the Cape/Islands. Any convective showers will help to enhance the wind as well. HREF indicating high probs of gusts over 55 mph on the Cape so we upgraded to a high wind warning here with wind advisory remaining across rest of the coastal plain from I-95 south and east. Another factor is that strong wind gusts will be persistent all day and into the evening so long duration may enhance any wind issues.

Then we will have to deal with strong west winds along and behind the cold front. This is a strong front with a strong pressure rise- fall couplet and sharp temp gradient. Soundings show quickly deepening boundary layer which will enhance mixing in the cold advection. Strongest gusts will be over the high terrain in northern MA, especially the Berkshires and potentially in portions of the CT valley where 55-60+ mph gusts are possible. The pressure rises are diminishing as they move east so peak winds will be diminishing further east, but soundings support a period of 45-55 mph gusts across rest of SNE along and behind the cold front. High wind watch for the Berkshires was expanded east to include the Worcester Hills and wind advisories were issued elsewhere.

Temps and potential snow... Strong cold advection behind the front will result in sharply falling temps Wednesday night from the 50s through the 30s a 3-6 hr period, with morning lows in the 20s. Wind chills by Thu morning will be in the single numbers and teens, and close to zero in the Berkshires. So quite a different feel from Wednesday evening.

While it will be drying behind the front, there is a short window with enough moisture for a brief changeover to snow before the precipitation ends. Not much accum expected with generally a coating, but 1- 2 inches accum possible in the Berkshires. There is a low risk for isolated icy spots as temps drop, especially where any minor accum occurs, but otherwise not a big concern as strong winds and rapid drying will dry out pavement before any freezing.

Coastal Flooding... We are forecasting up to a 2 ft surge for Providence which will still keep the total water level below 7 ft. Need a 3 ft surge for minor flooding which is unlikely at this time.

Long Term - Thursday Through Tuesday
Key Points

* Thursday - winter cold returns with wind chills in the teens!

* Friday - not as cold and remaining dry

* Weekend & early next week - mild but wet at times

Thursday... Cold blast behind departing system, with strong Cold Air Advection (850 mb temps -15C 18z Thu and -9C at 925 mb) into SNE. Sunshine and downsloping WNW winds will only yield highs of 30-35, upper 20s high terrain. Wind chills will be even colder, with WNW winds 15-25G40 mph, possibly up to 50 mph at times across the Berkshires. This will yield WC in the single digits and teens in the morning, but only coming up to the teens and low 20s.

Friday... Not as cold with mid/upper trough over southeast Quebec continuing to lift eastward. High pressure sliding southeast of New England will promote SSW return flow, allowing cold morning temps in the teens and 20s to rebound to 45-50 during the afternoon, along with sunshine.

Weekend into Early Next Week
Southwest flow will result in mild temps but also wet at times, as Gulf and Atlantic moisture advected northeast in the SW flow aloft. Large model spread in guidance here on timing the timing of this moisture, along with amplitude of downstream flow across the northwest Atlantic. Much of the guidance does agree on dry weather possibly lingering into Saturday.

Marine
Forecaster Confidence Levels:

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

Gale warnings continue for all waters for 2 periods of gale force winds. Strengthening low level jet will bring southerly gales to the waters late tonight into Wednesday evening with gusts to 45 kt, then post frontal westerly gales later Wednesday night. Reduced visibility in rain and fog tonight into Wednesday night.

Outlook /Thursday through Sunday/... Thursday: Strong winds with gusts up to 40 kt. Rough seas up to 14 ft.

Thursday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of rough seas.
Friday through Friday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Areas of seas approaching 5 ft.
Saturday: Winds less than 25 kt. Chance of rain.

Saturday Night: Winds less than 25 kt. Seas locally approaching 5 ft. Chance of rain.

Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...Wind Advisory from 7pm Wednesday to 7am EST Thursday for CTZ002. Wind Advisory from 1pm Wednesday to 7am EST Thursday for CTZ003-004. MA...Wind Advisory from 7pm Wednesday to 7am EST Thursday for MAZ005-006-012. Wind Advisory from 1pm Wednesday to 7am EST Thursday for MAZ007-013>015. High Wind Watch from Wednesday evening through Thursday afternoon for MAZ002>004-008>011-026. Wind Advisory from 7am Wednesday to 7am EST Thursday for MAZ016>021. High Wind Warning from 7am Wednesday to 7am EST Thursday for MAZ022>024. RI...Wind Advisory from 1pm Wednesday to 7am EST Thursday for RIZ001. Wind Advisory from 7am Wednesday to 7am EST Thursday for RIZ002>008.

Marine
Gale Warning from 7am Wednesday to 7pm EST Thursday for ANZ230. Gale Warning from midnight tonight to 1pm EST Thursday for ANZ231>235-237. Gale Warning from midnight tonight to 10am EST Thursday for ANZ236. Gale Warning from midnight tonight to 7pm EST Thursday for ANZ250-254>256. Gale Warning from 4am Wednesday to 7pm EST Thursday for ANZ251.