textproduct: Boston / Norton

WHAT HAS CHANGED

Small craft headlines issued for many of our waters tonight into Saturday morning.

KEY MESSAGES

- Dry with fall-like weather tonight through Sat night. Lows both nights mainly in the 40s-lower 50s. Highs Sat mainly in the 60s perhaps flirting with 70 in the lower CT River Valley.

- Next chance for rain Sunday into Monday. There remains uncertainty in the details such as coverage, timing, and amounts. Showers may linger through early next week. A coastal low pressure is possible late next week.

DISCUSSION

KEY MESSAGE 1...Dry with fall-like weather tonight through Sat night. Lows both nights mainly in the 40s-lower 50s. Highs Sat mainly in the 60s perhaps flirting with 70 in the lower CT River Valley.

A very pleasant fall-like airmass is on tap for the region tonight through Sat night. This as high pressure builds eastward across Quebec tonight and into northern New England/Canadian Maritimes Sat into Sat night.

Drier and cooler air works into the region tonight. Winds should decouple enough overnight for lows to drop into the 40s across many locations...but lower-middle 50s in some urban centers as well as the Cape/Islands where a stiff N breeze will keep temps from bottoming out. Plenty of sunshine on Sat...but cool NE flow will result in highs mainly in the 60s perhaps flirting with 70 in parts of the Lower CT River Valley. Coolest high temps Sat will be found along the immediate eastern MA coast, Cape and Islands where highs will be held in the lower to middle 60s.

High pressure slowly shifts east of the region Sat night. However...think there will be enough of a window for a good night of radiational cooling before thicker mid-level clouds move in toward daybreak. Low temps should be well down into the 40s in most locations with lower 50s in the urban heat island of Boston.

KEY MESSAGE 2...Next chance for rain Sunday into Monday. There remains uncertainty in the details such as coverage, timing, and amounts. Showers may linger through early next week. A coastal low pressure is possible late next week.

The latest guidance still suggests a widespread rainfall later Sunday into Monday morning. This is not looking like it will be an especially dynamic system. Still a wetting rain should overspread southern New England from west to east during the day. The most likely period for sustained rainfall should be Sunday night. Then the question becomes how quickly a front pushes south of our region Monday morning.

Right now, favoring dry weather for most of Monday, continuing through Wednesday. Some of the deterministic models suggest a slightly farther north position of this front, keeping a small chance for continuing precipitation towards the south coast. Given the strength of the high pressure over eastern Canada, have gone away from this particular solution.

Finally, the guidance suite is hinting at a possible coastal low pressure some time Thursday into Friday. However, there are rather large variances in track and timing. For example, the 12Z GFS has a low pressure over the Gulf of Maine at 8 AM next Friday. Meanwhile, the 12Z ECMWF has this same low pressure about 300 miles east of southern MD for this same time. Different positions also lead to different tracks due to interactions with a mid level trough. At this time, have low confidence in the forecast details late next week. It is a situation that will need to be monitored.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Forecaster Confidence Levels...

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

Tonight...High confidence.

VFR. N winds generally 10 knots or less...except 7-15 knots across the Cape/Islands with some 20+ knot gusts possible in those locales after midnight.

Saturday...High confidence.

VFR. Light NE winds become E...except for a few 20-25 knots gusts in the morning across the Cape and especially Nantucket.

Saturday night...High confidence.

VFR. Calm/light S winds.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Sunday through Wednesday/...

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

Sunday Night: MVFR/IFR conditions possible. Breezy. SHRA.

Monday: Mainly VFR, with local MVFR possible. Breezy. Slight chance SHRA.

Monday Night: VFR. Breezy.

Tuesday: VFR. Windy with local gusts up to 30 kt.

Tuesday Night: VFR. Windy with areas of gusts up to 35 kt.

Wednesday: Mainly VFR, with local IFR possible. Windy with gusts up to 35 kt.

MARINE

Forecaster Confidence Levels...

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

Tonight through Saturday night...High confidence.

As high pressure builds into Quebec tonight...expect a period of N wind gusts near 25 knots across many of our waters given good mixing in the cool air advection pattern over the relatively mild ocean. We did include Cape Cod Bay/Nantucket sound as they should see a period of good mixing with 925T dropping to between +5C and +7C and SST still on the order of +21C/+22C.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Chance of rain showers.

Sunday Night: Winds less than 25 kt. Rain showers. Local visibility 1 to 3 nm.

Monday: Low risk for Small Craft Advisory winds with gusts up to 30 kt. Seas locally approaching 5 ft. Chance of rain showers, slight chance of thunderstorms.

Monday Night: Moderate risk for Small Craft Advisory winds with areas of gusts up to 30 kt. Seas up to 5 ft. Chance of rain showers.

Tuesday: Strong winds with gusts up to 35 kt. Rough seas up to 11 ft. Slight chance of rain showers.

Tuesday Night: Strong winds with gusts up to 40 kt. Rough seas up to 12 ft. Slight chance of rain showers.

Wednesday: Strong winds with gusts up to 45 kt. Rough seas up to 13 ft. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents from Saturday morning through Saturday evening for MAZ007-015-016-019-022-024. RI...None. MARINE...Small Craft Advisory from 11 PM this evening to noon EDT Saturday for ANZ231-232. Small Craft Advisory from 8 PM this evening to noon EDT Saturday for ANZ250-251-254>256.