Marine Weather Net

Coastal Waters out 25 NM South of Marthas Vineyard and Nantucket Marine Forecast


THIS AFTERNOON

W
WINDS
20
KNOTS

TONIGHT

NW
WINDS
20 - 25
KNOTS

SAT

W
WINDS
20
KNOTS

SAT NIGHT

NW
WINDS
15 - 20
KNOTS

The Marine Weather Forecast In Detail:
ANZ255 Forecast Issued: 1016 AM EST Fri Mar 05 2021

SMALL CRAFT ADVISORY IN EFFECT THROUGH SATURDAY AFTERNOON
This Afternoon...W Winds Around 20 Kt With Gusts Up To 30 Kt. Seas 4 To 6 Ft.
Tonight...Nw Winds 20 To 25 Kt With Gusts Up To 30 Kt. Seas 4 To 7 Ft. Light Freezing Spray.
Sat...W Winds Around 20 Kt With Gusts Up To 25 Kt. Seas 4 To 6 Ft. Light Freezing Spray.
Sat Night...Nw Winds 15 To 20 Kt, Diminishing To 10 To 15 Kt After Midnight. Seas 4 To 6 Ft.
Sun And Sun Night...N Winds 10 To 15 Kt. Seas 2 To 3 Ft.
Mon Through Tue Night...W Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 2 To 4 Ft. 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
1006am EST Fri Mar 5 2021

Synopsis
Dry weather persists through the middle of next week. Colder than normal through the weekend. The pattern then moderates to warmer than normal conditions for the middle of next week.

Near Term - Until 6pm This Evening
10 AM

* Cold and blustery day with a mix of sun and clouds.

Per Storm Prediction Center mesoanalysis, core of cold air aloft stretches from Northeast PA into Lower Hudson Valley of NY eastward into CT/RI/MA, with 500 mb temps down to -32C to -33C! This is supporting a cold morning in progress (especially by early March standards) with temps slowly climbing thru the 20s. Feels colder given blustery NW winds 15-20 kt, gusting to 25-35 kt, yielding wind chills in the single digits and teens.

As expected, cold 850 mb temps today ranging from -12C to -14C across the region this afternoon. Model soundings support boundary layer mixing to almost this level, combined with downsloping WNW winds, these temps aloft will support highs 30-35 in the Coastal Plain including Boston, but highs only mid to upper 20s across the interior. These highs are about 10 degs below than normal, and it will feel colder given the blustery WNW winds.

Airmass is extremely dry with Storm Prediction Center mesoanalysis indicating PWATs down to a tenth of an inch. This is also reflective at the surface with subzero dew pts being observed across the area at 10 am. This will result in afternoon RH values in the 20 percent range. Hence, very dry airmass.

Mid/high clouds streaming across Northern MA into VT/NH and this is the result of slightly warmer airmass aloft (500 mb), ahead of the next reinforcing surge of colder air just across the border.

Short Term - 6pm This Evening Through 6pm Saturday
Low pressure lingers over Eastern Canada into Saturday, maintaining a surface pressure gradient over Srn New England although diminished from the levels of today. There will also be lingering clouds from the cold pool(a region of relatively cold air) aloft. But with continued dry air at the surface, expect dry weather through Saturday.

The wind may keep the air stirred tonight and prevent radiational cooling. With dew points in the single numbers, there should be room for temperatures to drop into the teens. Temps aloft will show similar values to today. Therefore will forecast similar max temps for Saturday.

Long Term - Saturday Night Through Thursday
Highlights... * A chilly but pleasant Sunday with plentiful sunshine and light winds. * Warming trend begins Monday with highs in the 50s and possibly 60s Tuesday into Thursday away from the immediate coast.

Saturday night into Sunday... A highly amplified H5 ridge that extends into the northern Canadian Prairies builds into the Great Lakes, helping to deepen the corresponding H5 trough over Eastern US. This development also helps to nudge the attendant upper closed low further east. On Saturday night, conditions look ideal for good radiational cooling thanks to diminishing winds, clear skies and remaining snow cover north and west of the I-95 corridor. Therefore, we lowered the low temperature on Saturday night to 10th percentile of guidance. On Sunday, 925mb temperatures moderate to between -7 to -9C. With mixing up to that level, expect highs in the 30s across most locations, except for upper 20s in the interior high terrain. With surface high pressure overhead, light winds and plentiful sunshine will make for a rather pleasant day on Sunday despite high temperatures running 5 to 10 degrees below normal.

Monday into Thursday... The new work week looks to feature a transition into a +AO/+NAO/-PNA regime, which is favorable for a more significant and prolonged warm up. In fact, the AO is forecast to go highly positive, which is a strong signal for building warmth. Along with the lack of snow cover away from the interior and downsloping effect from strong southwesterly flow, blended model guidance will likely be a little too cool with the high temperatures on Tuesday and Wednesday. Lending further confidence to anomalous warmth during this period is that both the NAEFS and ENS Situational Ensemble Awareness Table show heigheights at all levels and 1000mb temperatures rising to 90th percentile for Tuesday and 97.5th to 99th percentile for Wednesday and Thursday. Given such a strong signal for temperatures to overperform, have used the 90th percentile of guidance for forecast highs, yielding low to mid 50s on Tuesday and upper 50s to low 60s for Wednesday away from the immediate coast. Low temperatures overnight Tuesday into Wednesday as well as overnight Wednesday into Thursday are also adjusted using the 75th percentile of guidance as warm air advection continues in earnest.

As for precipitation chances, a passing shortwave to our north could produce some showers on Tuesday but it is way too early to pinpoint the impacts and timing of any precipitation. Then on Thursday, a cold front passage could produce some showers but models still differ significantly on the timing of the frontal passage. Overall, a mainly dry forecast is in store through at least mid week.

An interesting tidbit is that this past meteorological winter has been notable for the lack of anomalous warmth, unlike the previous winter. All four of our climate sites have gone a considerable amount of time without exceeding 50F for high temperature. Boston and Providence last saw above 50F on January 16 2021, with highs of 52 and 55F respectively. Hartford and Worcester last saw above 50F on Christmas Day last year, with highs of 63 and 61F respectively. This run is likely to come to an end by Tuesday. In fact, the CPC has a 70 to 80 percent probability of above normal temperatures for Southern New England in its latest 6 to 10 day outlook. Talk about a taste of spring!

Marine
Gusty northwest winds today with potential for 25 to 30 kt gusts. Winds diminish later tonight and Saturday with wind gusts Saturday around 20 kt. Seas 5 to 6 feet on the outer waters today, subsiding to 5 foot seas on the southern outer waters Saturday.

Light freezing spray will a factor through Saturday. Favorable conditions include air temps around freezing, sea temps 35F to 40F, and strong gusty northwest winds.

Expect Small Craft Advisory conditions today and tonight, diminishing below that level on Saturday.

.Outlook /Saturday Night through Tuesday/... Saturday Night: Winds less than 25 kt. Areas of seas approaching 5 ft.
Sunday through Sunday Night: Winds less than 25 kt.

Monday: Winds less than 25 kt. Seas locally approaching 5 ft.

Monday Night: Winds less than 25 kt.

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None.
MARINE...
Small Craft Advisory until 9am EST Saturday for ANZ231>235- 237-250-251. Small Craft Advisory until 4am EST Saturday for ANZ230-236. Small Craft Advisory until 5pm EST Saturday for ANZ254>256.