textproduct: Boston / Norton

WHAT HAS CHANGED

Gale Watch continues, with Small Craft Advisories issued for waters not covered by the Gale Watch. Strongest winds Wednesday night into Thursday remain focused on far southeastern Massachusetts, Cape Cod, and the Islands.

KEY MESSAGES

- Quiet and dry conditions through Wednesday afternoon. - Frontal passage Wednesday night into Thursday morning brings showers and gusty southwest winds, especially over far southeastern Massachusetts, Cape Cod, and the Islands.

- Full sun, seasonable temperatures and onshore breezes Friday into the weekend.

DISCUSSION

KEY MESSAGE 1...Quiet and dry conditions through Wednesday afternoon.

Mainly quiet weather for the rest of today and tomorrow. This afternoon, a weak cold front pushes into the region from the northeast. There is little to no moisture to work with, so expect a dry frontal passage with a mixture of clouds. As for Wednesday, the front drifts back to the northeast as a warm front, with southerly winds advecting moisture back into southern New England and PWATs rising to 1.4 to 1.6 inches. While we cannot rule out a WAA shower during the day, the general theme is for a drier day with increased cloud cover. Otherwise, a seasonably warm day with highs in the upper 70s and lower 80s.

KEY MESSAGE 2...Frontal passage Wednesday night into Thursday morning brings showers and gusty southwest winds, especially over far southeastern Massachusetts, Cape Cod, and the Islands.

Shower chances increase Wednesday night into Thursday morning associated with a cold front. Though this doesn't look to be a soaking event, it will be more showery in nature, where one town sees a heavier downpour while two towns over perhaps only a light rain. More impressive are the low-level winds. Depending on your flavor of guidance, 925 mb winds are 45 to 55 knots. However, the strongest winds aloft traverse southern New England predawn Thursday, which will limit the amount of wind that can mix down to the surface.

Thinking where overnight temperatures remain mild, across far southeastern Massachusetts, Cape Cod, and the Islands, there is the greatest chance for winds to mix down, with sub-advisory gusts of 30 to 40 mph. However, if temperatures were to be a few degrees warmer overnight in this area, this could allow for slightly deeper mixing. Though with the nocturnal inversion overhead, it will be difficult to realize those stronger winds aloft and transport them down to the surface. Nevertheless, it's something to monitor.

Currently, we feel the greatest impacts will be for the marine community. Around the Cape and Islands are Gale Watches for the potential of those stronger winds. By Thursday afternoon, the surface cold front is offshore. However, temperatures aloft are slower to lower, so it will still be fairly seasonable Thursday afternoon. Then comes a reinforcement of colder air Thursday night, with 925 mb temperatures falling from around +20C Thursday to +10C Friday.

KEY MESSAGE 3...Full sun, seasonable temperatures and onshore breezes Friday into the weekend.

Still looking at a really nice stretch of weather for Friday into much of the weekend, with the weather across Southern New England being dominated by a sprawling high pressure cell coming in from Canada. Expect full sun, low humidity levels and dry weather for the daytime hours with good radiational cooling supporting some cool nights Friday through Saturday night. It still looks like Sunday could offer the next chance for cloud cover and some light showers developing Sunday night into early Monday but these also don't look capable of washouts. Highs Fri and Sat into the mid to upper 70s with low humidity levels, except low 70s near the eastern coastlines. By Sunday highs should top out in the mid 70s to low 80s despite increasing cloud cover.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

18z TAF Update...

Through 00z...High confidence.

VFR, despite an increase in some mid level cloudiness. NW winds 5-10 knots, except sea breezes developing along portions of the immediate coast this afternoon, between 19-21z.

Tonight...High confidence.

VFR. Calm/light E winds.

Wednesday...High confidence.

VFR. SW wind gusts of 15-25 knots developing during the afternoon.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday Night through Sunday/...

Thursday: VFR. Strong winds with local gusts up to 40 kt. Slight chance SHRA.

Thursday Night: VFR. Breezy. Slight chance SHRA.

Friday: VFR.

Friday Night through Saturday Night:

Sunday: Breezy. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday Night: High confidence.

Winds and seas to remain below small craft advisory criterion tonight through Wednesday. Light E/SE winds tonight turn south and increase to around 10-15 kt early Wednesday, with S/SW winds increasing to around 20 kt Wednesday. Seas around 3 ft or less through Wednesday morning, but increase to around 4 ft offshore during the Wednesday daytime hours.

Looking at a period of gusty southwesterly winds Wednesday evening into Thursday ahead of a slow-moving frontal boundary. Gale Watches were maintained for the near-shore waters adjacent to Cape Cod where enough mixing near the land-sea interface could be enough to bump gusts into the borderline/marginal Gale range around 35 kt, but we have issued small craft advisories for the remaining nearshore and outer waters marine zones with SW gusts to 30 kt. Seas build to around 5-9 ft over the outer waters and 2-4 ft nearshore.

Outlook /Wednesday Night through Sunday/...

Thursday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Slight chance of rain showers.

Thursday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers, slight chance of thunderstorms.

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

Friday Night through Saturday Night: Winds less than 25 kt.

Sunday: Winds less than 25 kt. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory from 8 PM Wednesday to 8 PM EDT Thursday for ANZ230-235>237-250-251-254>256. Gale Watch from Wednesday evening through Thursday morning for ANZ231>234.