Marine Weather Net

Nantucket Sound Marine Forecast


THIS AFTERNOON

W
WINDS
5 KNOTS

TONIGHT

SW
WINDS
5 KNOTS

THU

SW
WINDS
5 KNOTS

THU NIGHT

W
WINDS
5 KNOTS

The Marine Weather Forecast In Detail:
ANZ232 Forecast Issued: 1007 AM EST Wed Jan 22 2020

This Afternoon...W Winds Around 5 Kt. Seas 1 Foot Or Less.
Tonight...Sw Winds Around 5 Kt. Seas 1 Foot Or Less.
Thu...Sw Winds Around 5 Kt. Seas 1 Foot Or Less.
Thu Night...W Winds Around 5 Kt. Seas 2 To 3 Ft.
Fri And Fri Night...Ne Winds 5 To 10 Kt. Seas 2 To 4 Ft.
Sat And Sat Night...E Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 4 To 6 Ft. Rain.
Sun...Sw Winds 15 To 20 Kt With Gusts Up To 25 Kt. Seas 4 To 6 Ft. A Chance Of Rain.
Sun Night...Nw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas 3 To 5 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
635am EST Wednesday Jan 22 2020

Synopsis
High pressure will be in control through the end of the week bringing dry weather and moderating temperatures. A storm is expected to impact the region Saturday into Sunday with rain near the coast and snow over the high elevation interior. Some light snow is possible Sunday night into early Monday as the storm exits, then mainly dry and seasonable conditions into Tuesday.

Near Term - Until 6pm This Evening
7 am

No big changes with this morning's update. Very quiet out there under high pressure with calm, decoupled winds and no clouds to speak of. Those clouds continue to try to spill over the northern Berkshires but they've not been able to hold together and the moisture should diminish with time, so expecting a clear day all around. Not even any ocean effect clouds to deal with today.

Previous Discussion... Mid level ridging builds into New Eng from the Gt Lakes today while high pressure in control at the surface. Some high clouds may spill over the ridge this morning, otherwise mostly sunny skies as the column is quite dry. Moderating low and mid level temps will result in a nice temp recovery after a cold start to the day. Highs will reach the mid/upper 30s across much of the region with light winds.

Short Term - 6pm This Evening Through 6pm Thursday
High pressure remains in control through Thursday with clear skies and light winds. Another cold night tonight with good radiational cooling. Leaned toward coldest guidance which yields lows mostly in the teens with single numbers in the CT valley. Then continued airmass moderation on Thu will allow highs to reach low/mid 40s.

Long Term - Thursday Night Through Tuesday
Highlights... * Above normal temperatures Friday with continued dry weather

* Coastal storm this weekend brings rain/snow Sat into early Monday. Best chance of snow in the interior. Light snow regionwide by late Sun/early Monday as the system exits.

* Gusty winds over the waters late Saturday and Sunday

* Drying out Monday - Tuesday

Details... Thursday night through Friday night... Dry and quiet weather continues through the end of the work week under a ridge of high pressure. Not expecting full sun as we begin to see our first signs of the approaching storm system with upper level moisture/cirrus deck moving in Thursday night and Friday (good sunrise Friday perhaps?). Dry with breaks of sun and well above average temperatures expected as SW flow on the back side of the high draws in milder air. Highs on Friday will be in the mid 40s (compared to normals in the mid 30s). Decent radiational cooling is possible Thursday night with decoupled winds but the advancing high clouds may keep things warmer than they could otherwise achieve; leaning toward MOS guidance with lows in the 20s.

Saturday and Sunday... Confidence is high that the weekend will be unsettled, with a strong coastal storm breaking our streak of quiet weather. At the synoptic scale we see a digging 500 mb trough and surface low over the Ohio Valley move into the mid-Atlantic, spawning a secondary low along the frontal boundary which approaches Long Island Saturday afternoon. The low then crosses southern New England. An important variable for rain/snow delineation will be where the low center crosses. Unfortunately for us low elevation snow lovers, the trend has not been our friend, with a steady shift north in the low track over the last several model runs. Things aren't set in stone yet of course, but they don't look favorable for significant snows outside of the high elevation interior. For instance, nearly all of the EPS ensemble members place the low track somewhere over southern New England (as opposed to further south offshore which would be more favorable for pulling in cold air). The 700 mb low looks to pass directly overhead, which typically is too far north as well. This together with the warm antecedent airmass, and things just look too warm for snow outside of the higher elevations of the Berkshires and Worcester Hills, even with the high to our northeast. We'll have to see if that can provide any/enough cold air drainage to make a difference, but it doesn't look super favorable at the moment. One thing that high will do, though, is keep this system around longer than the quick hitter we saw last weekend. Precipitation begins Saturday morning in western MA/CT and (though becoming less widespread/heavy on Sunday) doesn't come to an end until sometime early Monday. As stated before, this will likely be more of a soaking rain event for most, changing to novelty snow showers late Sunday/early Monday as the system moves off and colder air is wrapped around. This would likely end up as a dusting to an inch at most. However, where we do see snow for the duration, there is enough Quantitative Precipitation Forecast (up to >1") that snowfall totals could be significant and impactful. Stay tuned. The pressure gradient tightens as the low passes Sat night/Sunday which will lead to gusty winds, mainly along the immediate coast and over the waters. Gale headlines may be needed.

Monday and Tuesday... Drying out Monday and Tuesday though some light snow showers may linger, especially over eastern MA early on Monday. High pressure moves in to replace the low and high temperatures return to just above seasonal values, in the upper 30s, with a warming trend toward mid week.

Marine
Short Term /through Thursday/...High confidence.

Light winds and seas through the period as high pressure over the waters.

Outlook /Thursday Night through Sunday/... Thursday Night: Winds less than 25 kt. Seas locally approaching 5 ft.
Friday: Winds less than 25 kt. Seas up to 5 ft.

Friday Night: Winds less than 25 kt. Areas of rough seas.
Saturday: Low risk for Small Craft Advisory winds with local gusts up to 30 kt. Rough seas up to 10 ft. Chance of rain.

Saturday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 14 ft. Rain.

Sunday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 14 ft. Chance of rain.

NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None. MARINE...None.