Marine Weather Net

Nantucket Sound Marine Forecast


TONIGHT

S
WINDS
5 KNOTS

THU

NE
WINDS
5 - 10
KNOTS

THU NIGHT

N
WINDS
10
KNOTS

FRI

N
WINDS
10
KNOTS

The Marine Weather Forecast In Detail:
ANZ232 Forecast Issued: 705 PM EDT Wed May 29 2024

Tonight...S Winds Around 5 Kt. Seas Around 2 Ft. Wave Detail: E 2 Ft At 9 Seconds And Sw 1 Foot At 2 Seconds. Patchy Fog After Midnight. A Slight Chance Of Rain After Midnight.
Thu...Ne Winds 5 To 10 Kt, Becoming N With Gusts Up To 20 Kt In The Afternoon. Seas Around 2 Ft. Wave Detail: Sw 1 Foot At 2 Seconds And Ne 1 Foot At 2 Seconds. A Chance Of Rain.
Thu Night...N Winds Around 10 Kt. Gusts Up To 20 Kt In The Evening. Seas 2 To 3 Ft. Wave Detail: N 1 Foot At 3 Seconds And S 1 Foot At 7 Seconds.
Fri...N Winds Around 10 Kt. Seas Around 2 Ft. Wave Detail: N 1 Foot At 3 Seconds And E 1 Foot At 7 Seconds.
Fri Night...W Winds 5 To 10 Kt, Becoming Nw After Midnight. Seas 1 Foot Or Less. Wave Detail: Ne 1 Foot At 3 Seconds And Nw 1 Foot At 3 Seconds.
Sat And Sat Night...Nw Winds 5 To 10 Kt. Seas Around 2 Ft. Wave Detail: N 1 Foot At 4 Seconds And Se 1 Foot At 7 Seconds.
Sun Through Mon Night...Sw Winds 5 To 10 Kt. Seas Around 2 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
726pm EDT Wednesday May 29 2024

Synopsis
Other than a few brief showers/thunderstorms this afternoon and early evening, mainly dry, pleasant warm weather prevails. Low pressure then brings a more widespread rain, moderate to heavy at times later tonight into Thursday morning, then slowly dries out Thursday afternoon from west to east. Drier weather with plentiful sunshine for Friday. After a few days of temperatures at or slightly cooler than normal, the weekend into Monday offers a warming trend toward above normal temperatures and still tolerable humidity levels. Drier weather should generally prevail this weekend into at least Tuesday.

Near Term - Until 6am Thursday Morning
3 PM

* Other than a few showers/isolated thunderstorm, mainly dry this afternoon and early evening

* More widespread rain after midnight into THU AM

This afternoon & early evening... 12z models have trended drier for this afternoon and early evening, as it appears there will be more than expected subsidence over SNE between departing s/wv exiting ME and approaching s/wv currently over southwest PA. Thus, shower/thunderstorm activity is expected to be more isolated (not widespread). Radar beginning to pickup some scattered showers entering western MA/CT.

Still low risk of an isolated storm with small hail and brief heavy downpours in the stronger cells. Otherwise, just lots of diurnal scu/cu today given the cyclonic flow and cold air aloft (-18C at 500 mb). Despite the steep mid level lapse rates, diurnal buildups out the window here and on satellite, is limited given dew pts only in the upper 40s and lower 50s. These low dew pts yielding very pleasant conditions for late May, with low humidity and temps slightly warmer than normal, as highs climb into the mid/upper 70s away from the coastline.

Overnight... Mainly dry this evening (after any diurnal showers/thunderstorms dissipate), then bands of rain overspread the region later tonight and become fairly widespread. This is in response to a potent s/wv currently over southwest PA advects eastward. In fact, models are suggesting this will take on more of a cool season rain event, as s/wv is fairly baroclinic for late spring, with mid level Fgen around 850 mb. In addition, models are hinting at some instability above this layer and the response is for bands of moderate to heavy rain. This already is present on radars across PA. Exact location of these bands as they traverse SNE varies from model to model, ranging from northern MA to the south coast. This instability may be sufficient for isolated thunder, but more likely, enhancing rainfall potential, with moderate to heavy rain at times late tonight and towards Thu morning. Seasonably cool tonight with lows in the 50s. Light and variable winds become NE toward morning and may become gusty 15-20 mph towards morning, as surface wave develops along or just offshore.

Short Term - 6am Thursday Morning Through Thursday Night
3 PM

Highlights:

* Bands of moderate to heavy rain THU AM * Drying trend Thupm from west to east * Cooler given cold temps aloft

Thursday... As mentioned in the short term section above, baroclinic s/wv and attending surface low move across SNE Thu AM. 850 mb Fgen and weak instability above this layer will yield bands of moderate to heavy rain at times. Widespread rainfall totals of 0.25 to 0.75 inches, with local amounts possibly 1+ inches. Could be a slowam commute given periods of moderate to heavy rain yielding minor street/highway flooding.

Mid level trough axis moves east of the region after 18z along with dry slot ovespreading the area. Thus, drying trends in the afternoon from west to east, along with a breaks of sunshine possible, especially late in the day. Much cooler tomorrow given cold pool(a region of relatively cold air) aloft, combined with NNE onshore flow along with precipitation in the AM. Highs only in the 60s. Coolest along the eastern MA coastline, especially with NNE winds 15-20 mph providing cool/damp/raw conditions. Highs closer to 70 in the CT River Valley, including Hartford and Springfield.

Thursday night... Mainly dry weather, although clouds and spotty light rain/drizzle may linger across the outer Cape to Nantucket given moist NNE flow. Otherwise, dry and cool weather with lows 45-50 most of the region. Given the cooler regime, we blended in some of the cooler MOS guidance to derive min temps.

Long Term - Friday Through Wednesday
3 PM

Highlights

* High pressure supports mostly dry/quiet weather through the middle of next week

* Temperatures gradually increasing through the middle of next week

Through Next Wednesday

The extended forecast looks to be very quiet from Friday forward as a broad upper-level ridge builds in behind a departing short-wave trough on Friday afternoon. This will support high pressure at the surface that will support mainly dry/sunny conditions through at least early next week. Temperatures will be on the uptick through this time range as well with seasonable temperatures on Friday in the low to mid 70s gradually increasing to the mid 80s by next Tuesday. Low temps will follow a similar pattern with lows in the upper 40s/low 50s Friday night increasing to the low 60s by Wednesday morning. The upper level ridge supporting this pattern looks to possibly breakdown mid to late next week with a potentially robust upper trough digging down from The Great Lakes. This would be the next possibility for any active/unsettled weather beyond Friday.

Marine
Forecaster Confidence Levels:

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

3 PM

Tonight...mainly dry and good vsby this evening, then rain overspreads the waters after midnight. Light onshore winds become NNE overnight, 15-20 kt.

Thursday...weak/broad low pressure moves over or just offshore, with NNE winds 15-20 kt across the MA/RI waters, along with reduced vsby in rain in the morning. Then slow improvement west to east in the afternoon.

Thursday night...NNE winds 10-15 kt may yield spotty light rain/drizzle across the eastern MA waters. Otherwise, dry weather and good vsby for the RI waters.

Outlook /Friday through Monday/... Friday through Sunday: Winds less than 25 kt.

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

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

Marine
None.