textproduct: Boston / Norton

WHAT HAS CHANGED

No changes to current weather headlines. Confidence in an impactful coastal storm for Friday into this weekend is increasing.

KEY MESSAGES

- Dry, cool, and breezy conditions continue through Thursday.

- Monitoring the potential for a strong coastal low to arrive late week, bringing chances for strong winds, rainfall, and coastal flood/erosion concerns through the weekend.

DISCUSSION

KEY MESSAGE 1...Dry, cool, and breezy conditions continue through Thursday.

Not anticipating much change to the forecast through Thursday. A sprawling high pressure to our north will maintain cooler conditions with gusty east to northeast winds. There should be a brief period this evening where gusts subside before another surge of colder air starts the gustiness again. The strongest gusts should be from late morning into the afternoon Wednesday. Slightly less breezy conditions for Thursday.

Across the southern coastal waters, Gale Warnings remain in effect for Wednesday and Thursday.

KEY MESSAGE 2...Monitoring the potential for a strong coastal low to arrive late week, bringing chances for strong winds, rainfall, and coastal flood/erosion concerns through the weekend.

While there is still a large amount of uncertainty in the guidance, the overarching trend is indicating the low slowly meanders north and retrograding west into the waters south of Block Island and Nantucket; however, how close the low tracks to the southern coast is still a large question. It is important to note that the exact track and strength of the low will strongly influence the timing and magnitude of gusts, QPF, and how far inland the rain extends. The latest ECMWF is indicating the low passes closer to Long Island whereas the latest GFS is showing the low passing closer to the outer Cape and Nantucket. Depending on the track the low takes, the onset of the strongest winds could be as early as Friday evening or as late as Saturday afternoon. Regardless, confidence is slowly increasing in at least Gale Force winds (34kts/40mph), with the possibility of Storm Force winds (48kts/55mph) Friday night/Saturday, across the southern waters leading to an upgrade of the Gale Watch to a Gale Warning for the southern and southeastern waters.

This prolonged period of gusty northeasterly winds will build rough seas and raise the threat for coastal flooding and erosion, especially for east facing beaches and harbors. Latest coastal flooding guidance from the Stevens Institute shows greatest risk for at least minor coastal flooding for Nantucket Harbor around the high tidal cycles Friday, Friday night, and Saturday. The coastal flooding risk is slowly increasing for Boston Harbor as well, although to a slightly lesser extent compared to Nantucket.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

06Z update...

Through 12Z...High confidence.

NE winds of 5 to 15 kt tonight with 20-25 kt gusts at times across the southeast New England coast and 25-30 kt for Nantucket.

Wednesday and Wednesday Night...High confidence.

Mainly VFR. NE winds of 10 to 20 kt with gusts of 20 to 30 kt, strongest towards the southeast New England coast. Gusts near 35 kt for Nantucket.

Thursday...High confidence.

VFR, outside of MVFR cigs over ACK. NE winds of 10 to 20 kt with gusts of 20 to 30 kt, strongest towards the southeast New England coast. Gusts near 35 kt for Nantucket.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Thursday through Sunday/...

Thursday: VFR. Windy with gusts up to 35 kt.

Thursday Night: VFR. Strong winds with local gusts up to 40 kt.

Friday: VFR. Strong winds with gusts up to 45 kt. Chance SHRA.

Friday Night: VFR. Strong winds with gusts up to 40 kt. Chance SHRA.

Saturday: VFR. Strong winds with gusts up to 40 kt. Chance SHRA, slight chance TSRA.

Saturday Night: Mainly VFR, with local MVFR possible. Strong winds with local gusts up to 40 kt. Chance SHRA, slight chance TSRA.

Sunday: Mainly VFR, with areas MVFR possible. Windy with gusts up to 35 kt. Chance SHRA, slight chance TSRA.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday Night...High Confidence.

NE winds 15-20 kt with gusts up to 25 kt at times will continue, as strong 1030+ mb high pressure over southeast Ontario moves eastward into Quebec. This northeast fetch will yield rough seas on the ocean waters. Dry weather and good visibility prevail. Potential for gale force gusts appear to hold off until Wed and beyond. Seas increase to 6-13 ft outside the bays, harbors and sounds by Wednesday evening and night.

Outlook /Thursday through Sunday/...

Thursday: Strong winds with gusts up to 45 kt. Rough seas up to 16 ft.

Thursday Night: Moderate risk for gale force winds with local gusts up to 45 kt. Rough seas up to 17 ft. Chance of rain showers.

Friday: gale force winds with gusts up to 45 kt. Rough seas up to 20 ft. Chance of rain showers.

Friday Night: gale force winds with gusts up to 45 kt. Rough seas up to 22 ft. Chance of rain showers, slight chance of thunderstorms.

Saturday: gale force winds with gusts up to 45 kt. Rough seas up to 21 ft. Rain showers likely, chance of thunderstorms.

Saturday Night: Strong winds with local gusts up to 45 kt. Rough seas up to 19 ft. Rain showers likely, slight chance of thunderstorms.

Sunday: Strong winds with gusts up to 35 kt. Rough seas up to 16 ft. Rain showers likely, slight chance of thunderstorms.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ230-250- 251. Gale Warning from 8 PM this evening to 8 PM EDT Thursday for ANZ231-254. Gale Warning from 5 AM early this morning to 8 PM EDT Thursday for ANZ232>235-237-281. Small Craft Advisory from 5 AM early this morning to 8 PM EDT Thursday for ANZ236. Gale Warning until 8 PM EDT Thursday for ANZ255-256-282-283.