Nantucket Sound Marine Forecast
|Tonight...S Winds Around 5 Kt. Seas 1 To 2 Ft.|
|Fri...E Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Afternoon. Seas 1 To 2 Ft. A Chance Of Showers. Vsby 1 Nm Or Less.|
|Fri Night...E Winds 5 To 10 Kt. Gusts Up To 20 Kt In The Evening. Seas Around 2 Ft. Patchy Fog. A Chance Of Showers.|
|Sat...Ne Winds 5 To 10 Kt. Seas 1 To 2 Ft. Patchy Fog. Vsby 1 To 3 Nm.|
|Sat Night...N Winds Around 5 Kt, Becoming Nw Around 5 Kt After Midnight. Seas 1 Foot Or Less.|
|Sun And Sun Night...Sw Winds 5 To 10 Kt. Seas 1 Foot Or Less.|
|Mon Through Tue...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 2 Ft.|
|Tue Night...Sw Winds 10 To 15 Kt With Gusts Up To 20 Kt. Seas Around 2 Ft. A Chance Of Showers And Tstms. Winds And Seas Higher In And Near Tstms. 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.|
Area Forecast Discussion|
National Weather Service Boston/Norton MA
323pm EDT Thu August 6 2020
Dry and pleasant weather will continue tonight. A couple of fast moving disturbances should bring a few showers/thunderstorms Friday and Saturday, but a washout is not expected with dry weather dominating much of this time. Warmer and more humid weather returns early next week, along with chances for showers and thunderstorms, especially by Wednesday and Thursday when a slow moving cold front approaches the region.
Near Term - Until 6am Friday Morning
A shortwave will drop south into the Eastern Great Lakes tonight. While dry weather will prevail overnight, expect an increase in mid/high level cloudiness as the night wears along. Despite an increase in clouds, light winds and a relatively dry airmass in place for this time of year will allow for pleasant temperatures. Overnight lows should bottom out mainly in the lower to middle 60s with some upper 50s possible across western MA.
Short Term - 6am Friday Morning Through Friday Night
Friday... A shortwave will cross the region from the southwest on Friday. This will result in an abundance of cloudiness and the risk of a few showers, mainly south of the MA Turnpike. The best chance for a period of steady showers and perhaps a rumble or two of thunder will be near the south coast, Cape, and especially the outer Islands. There is some elevated instability, but the best forcing/instability will be south of our region. So there is some uncertainty whether areas near the south coast see just a few showers or a period of steadier/more widespread showers.
High temps on Friday will mainly be in the upper 70s to the lower 80s given an abundance of cloudiness, but some peeks of sunshine are possible.
Friday night... Another shortwave will approach the region Friday night. This will be somewhat sharper than the one during day. This will steepen mid level lapse rates a bit and result in some elevated instability. Should generate some scattered showers and perhaps embedded thunderstorms particularly during the overnight hours. Areal coverage somewhat uncertain, but its possible CAMS radar simulations are underdone based on sharpness of the shortwave. Low temperatures will be in the 60s.
Long Term - Saturday Through Wednesday
Highlights... * Few storms possible Saturday * Turning warmer/more humid early next week - possible heat wave? * Chances for storms increase by Wed/Thu
Typical mid summer pattern taking shape through next week as broad upper ridge across southern 2/3 of country results in zonal flow as main band of westerlies shifts to our north. This allows heat/humidity to return early next week with potential for another heat wave in some interior locations. Should be back in lower 90s Monday and Tuesday, though it's possible cloud cover may keep temps in 80s by Wednesday/Thursday. Also looks like a favorable pattern for nighttime/early morning low clouds and fog near south coast due to persistent SW flow.
As far as rainfall is concerned, could see lingering showers/storms Saturday morning, then environment becomes a bit less favorable during afternoon as upper trough/cold pool(a region of relatively cold air) shifts east and we come under weak subsidence in its wake. Chances for storms increase starting Monday, although best shot appears to be Wednesday and Thursday as slow moving cold front approaches New England, which is expected to eventually wash out near south coast. Not looking for widespread soaking rainfall, more like usual scattered showers/storms.
Tonight through Friday night...High confidence. Winds/seas will remain below SCA (Small Craft Advisory) thresholds given a relatively weak pressure gradient. Main concern for mariners will be the risk for a few thunderstorms, especially across our southern waters later Fri into Fri night.
Outlook /Saturday through Monday/... Saturday: Winds less than 25 kt. Slight chance of rain showers, slight chance of thunderstorms.
Saturday Night through Sunday Night: Winds less than 25 kt.
Monday: Winds less than 25 kt. Slight chance of rain showers, slight chance of thunderstorms.
NOAA Boston MA Office: Watches - Warnings - Advisories
CT...None. MA...None. RI...None. MARINE...None.