textproduct: Boston / Norton

WHAT HAS CHANGED

Gale Warnings have begun to be replaced by Small Craft Advisories for near shore southern waters, and this will continue over the next 24 hours.

KEY MESSAGES

-Cooler day on Friday with plenty of sun and diminishing wind.

- Prolonged stretch of dry weather with seasonable temperatures prevails this weekend into much of next week.

DISCUSSION

KEY MESSAGE 1...Cooler day on Friday with plenty of sun and diminishing wind.

Friday will continue the stretch of beautiful Fall weather for the region as we say goodbye to any influence from Subtropical Storm Josephine, replaced by building high pressure encroaching from the north. The weakening gradient will mean less of that northerly wind through the day. After winds initially start out breezy, gusting 15- 25 mph they'll end the day much lighter. Overnight in fact, under high pressure winds will become calm under clear skies, so lows were trended toward the colder MOS guidance, in the upper 20s to low 30s. This, after a cooler day on Friday after cold advection kicks in aloft; 925mb temps drop from 9C today to 0-1C on Friday leading to highs in the 50s.

KEY MESSAGE 2...Prolonged stretch of dry weather with seasonable temperatures prevails this weekend into much of next week.

A prolonged stretch of dry but pleasant autumn weather is in store for Southern New England spanning this weekend then continuing into a large portion of the upcoming workweek. Expansive area of surface high pressure of around 1030-1034 mb will remain anchored across the Northeast and mid-Atlantic region, with mild days and cool nights with strong diurnal temperature ranges. About the only nuanced difference is that a cold front sags southward Monday night into Tuesday with a cooler northern-stream airmass filtering southward; but the front is moisture-starved and only seems capable of producing some enhanced cloudiness Monday evening and a cooldown in high temps moving into next week. Mildest days look to be this weekend with temperatures in the mid to upper 60s, but there could be a shot at 70 degrees with several days of dry weather serving as a mild feedback mechanism for overachieving maximum temps over guidance. Highs then cool off into the mid 50s to low 60s for early next week as the cooler lower-level airmass works it way in (925 mb temps dip to around +2 to +4C), only modifying toward mid to late next week.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

Forecaster Confidence Levels...

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

18Z TAF Update:

This afternoon...High confidence in trends.

VFR. NE winds of 15 to 25 kt along the eastern and southeastern coast, with gusts of 25 to 40 kt. Strongest gusts expected at ACK, with lower gusts along the coastal plain. Farther inland, N winds of 10 to 14 kt with gusts of 20 to 25 kts.

Tonight...High confidence.

VFR. N/NNW winds diminishing through the evening but remaining breezy; strongest winds will be eastern and southeastern coast terminals, with sustained speeds of 10 to 15 kt and gusts of 20 to 30 kts.

Friday...High confidence.

VFR. Northerly winds across much of the region, though winds remain elevated east/southeast of I-95, with sustained speeds of 8 to 12 kt and gusts of 18 to 25 kts. Winds gradually decrease through the afternoon/evening Friday in those locations.

Friday night...High confidence.

VFR. Winds light and variable to calm.

KBOS Terminal...High confidence in TAF.

VFR. Gusty northerly winds continue today, with sustained speeds of 10 to 14 kt and gusts of 25 to 30 kt. Gusts decrease after 21Z this afternoon, potentially diminishing for a period early this evening. A front moves through 00-03Z bringing another period of gusts 18-25 kts out of the N. Marginal gusts may stick around through the early afternoon Friday before diminishing.

KBDL Terminal...High confidence in TAF.

Outlook /Friday Night through Tuesday/...

Saturday through Monday: VFR.

Monday Night through Tuesday: VFR. Breezy.

MARINE

Forecaster Confidence Levels...

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

Through Friday night...High confidence in hazardous marine conditions.

Dangerous to life-threatening marine conditions continue as Subtropical Storm Josephine remains offshore of southern New England. Strong high pressure to the north, combined with Josephine to the southeast, maintains a tight pressure gradient across the coastal waters, resulting in persistent northeast winds and large seas.

Gale Warnings remain in effect across most coastal waters through at least 8 PM this evening, with northeast wind gusts generally ranging from 30 to 45 kt. As Josephine tracks northeast into the North Atlantic, winds gradually diminish from west to east this evening. Gale Warnings across the waters west of Nantucket and Martha's Vineyard are expected to expire at 8 PM, with Small Craft Advisories needed thereafter for lingering gusty winds and elevated seas. Farther east, gale-force gusts will persist longer, with Gale Warnings continuing through early Friday afternoon. Once these warnings expire, Small Craft Advisories will likely be needed as winds gradually subside but seas remain elevated.

Marine conditions continue to improve Friday night and into the weekend as Josephine pulls farther away and high pressure builds into southern New England. However, elevated seas may linger beyond the strongest winds.

Outlook /Friday Night through Tuesday/...

Saturday: Winds less than 25 kt. Areas of rough seas.

Saturday Night: Winds less than 25 kt. Local rough seas.

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

Sunday Night through Monday Night: Winds less than 25 kt.

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 8 AM EDT Friday for ANZ230-233>235- 237. Gale Warning until 2 PM EDT Friday for ANZ231-232-250-251-254- 255-280>282. Gale Warning until 8 PM EDT this evening for ANZ256-283.