textproduct: Boston / Norton

WHAT HAS CHANGED

No significant changes to the forecast.

KEY MESSAGES

- Mostly dry weather prevails through Sunday with the exception of a few scattered showers Thursday. Highs consistently in the 60s after a warmer Thursday. Saturday morning may be frosty in spots.

- The next quick moving round of rain comes Sunday evening and overnight, exiting sometime on Monday though confidence in exact timing is low. Not expecting any flooding or damaging winds at this time.

DISCUSSION

KEY MESSAGE 1...Mostly dry weather prevails through Sunday with the exception of a few scattered showers Thursday. Highs consistently in the 60s after a warmer Thursday. Saturday morning may be frosty in spots.

High pressure dominates during this stretch of weather once we get past today as a pre-frontal trough and a moisture starved surface cold front coming swinging through this morning. Just enough moisture to squeeze out some isolated showers, mainly in the early morning (west) and late morning/early afternoon (east). Kept only a slight chance of showers at most, though many will stay dry. After a period of increased cloudcover with the frontal passage clear skies return in the afternoon and overnight. As sprawling high pressure expands overhead this will lead to cool and dry weather through much of if not all of Sunday. Cool NW flow around the high causes 925mb temps to drop from 15C today to 8-10C Fri/Sat leading high temps to struggle to escape the low to mid 60s. The airmass moderates Sunday as return flow kicks in behind the exiting high.

KEY MESSAGE 2...The next quick moving round of rain comes Sunday evening and overnight, exiting sometime on Monday though confidence in exact timing is low. Not expecting any flooding or damaging winds at this time.

Confidence remains moderate to high that our next rain event arrives late Sunday/Sunday night and is quite progressive as the remnants of Tropical Storm Isaias are swept up in a northern stream trough. This ushers it through rather quickly before deepening over the Gulf of Maine. While moisture parameters are good, at least over southern parts of the area, the progressive nature of the system will limit rainfall amounts and mitigate flooding issues. On the whole this looks to be a fairly typical rain maker for the region without hazards from flooding or damaging winds. Guidance generally paints a picture of a quarter inch or less for northern MA to 1.25" along the south shore in closer proximity to the better forcing and moisture. Ensemble probabilities of >1" of rain are essentially NIL except for 10-20% along the immediate south coast.

AVIATION /06Z THURSDAY THROUGH MONDAY/

Forecaster Confidence Levels...

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

06z TAF Update...High confidence.

VFR conditions continue through Friday. S winds of 5-15 knots early this morning with some 20+ knot gusts at times. A few brief passing showers possible mainly Thu morning...but this would be short- lived. WSW wind gusts of 15 to 25 knots expected Thu...but these should diminish and become W by Thu night. VFR Friday with W wind 10-15 kts gusting to 20 kts.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Friday Night through Monday/...

Friday Night through Saturday Night: VFR.

Sunday: VFR. Breezy.

Sunday Night: Mainly VFR, with local IFR possible. Chance SHRA.

Columbus Day: Mainly VFR, with areas MVFR possible. Chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Tonight through Friday...High confidence.

A SW low level jet ahead of an approaching cold front will result in SW wind gusts of 20-25 knots early this morning and persisting into Thu afternoon. Small craft advisories are in effect for most of our waters. Wind gusts should drop below small craft thresholds later Thu and especially Thu night. Friday high pressure will be approaching leading to W winds 10-15 kts gusting to 20 kts.

Outlook /Friday Night through Monday/...

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

Saturday through Sunday: Winds less than 25 kt.

Sunday Night: Winds less than 25 kt. Local rough seas. Chance of rain showers.

Columbus Day: Winds less than 25 kt. Rough seas up to 9 ft. Chance of rain showers, slight chance of thunderstorms.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 3 PM EDT this afternoon for ANZ231>235-237-254>256. Small Craft Advisory until 11 AM EDT this morning for ANZ250- 251.