textproduct: Boston / Norton

WHAT HAS CHANGED

Updated aviation section for 12Z TAFs.

KEY MESSAGES

- Quiet weather continues into the first half of the week.

- Warmer, breezy and more humid weather briefly returns Wednesday into Thursday, with a cold front bringing a risk for light rain showers Thursday, clearing offshore by Thursday early evening.

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

DISCUSSION

KEY MESSAGE 1...Quiet weather continues into the first half of the week.

The tranquil Labor Day weather will continue into Tuesday under the influence of building high pressure at the surface and in the mid levels. As the sprawling 500 mb ridge shifts east from the Ohio Valley height rises will contribute to continued dry weather and a warming airmass. 850 mb temps increase a few degrees to ~11C under dry NW flow. This will result in high temperatures just a few degrees north of average, in the upper 70s (higher elevations and along the coasts) to the low 80s). Dewpoints will be higher than Monday, but still comfortable in the mid to upper 50s. Under high pressure winds will be light with sea breezes along the coastline.

KEY MESSAGE 2...Warmer, breezy and more humid weather briefly returns Wednesday into Thursday, with a cold front bringing a risk for light rain showers Thursday, clearing offshore by Thursday early evening.

We begin to turn warmer and also a bit more humid than recently by Wednesday, ahead of a cold front which will very slowly progress southward into Southern New England by early Thursday morning. SW winds will also pick up by Wednesday afternoon but especially Wednesday night into early Thursday, particularly for the south coast, Cape and Islands. 950 mb SW jet upwards of 50 kt is depicted on the GFS along the south coast Wednesday night into Thursday. Gusts Wednesday night along the south coast, Cape and Islands could reach up to 40 mph if we can mix, but thinking gusts clock in a little less since profiles are warming aloft. On the waters potential exists for gale headlines along the southern waters, but gusts over land don't seem worthy of headlines.

Even though PWATs rise to around 1.5-1.8", there isn't an especially strong signal for significant rain as the front pushes southward on Thursday. Most of the ensembles and AI-based guidance seem pessimistic on rain chances, perhaps due to westerly flow at sfc and aloft, so left a 25-30% PoP mention for Thursday with the front moving southward/offshore by Thursday afternoon.

Highs Wednesday and Thursday should be similar both days in the upper 70s to mid 80s, but lows Wednesday night should be somewhat sticky with lows in the mid to upper 60s with dewpoints in the mid to upper 60s. More substantial cooling and drying takes place Thursday night post-frontal, with lows in the mid 50s to lower 60s.

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

A sprawling 1024 mb high pressure cell ridges into New England on Friday with moderately strong cool and dry advection and onshore NE winds taking hold through Saturday night. Expecting full sun, low humidity levels and dry weather Friday through Saturday night. Airmass starts to modify/warm up some into Sunday; increasing cloud cover by late Sunday/Sunday night ahead of a weak cool frontal boundary, but at least the daytime hours should end up largely dry.

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 MONDAY THROUGH SATURDAY/

Forecaster Confidence Levels...

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

18z TAF Update...

This afternoon and Tonight...High confidence.

VFR. NW winds 10-15 kt with gusts up to 20 kt. Winds diminish this evening between 22-00z and become more WNW overnight.

Tuesday...High confidence.

VFR. NW winds around 5-10 kt. Chance for localized seabreezes towards the late afternoon hours around 20-21z. Will continue to monitor.

Tuesday night...High confidence.

VFR. Winds calm.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Saturday/...

Wednesday: VFR. Breezy.

Wednesday Night: VFR. Windy with local gusts up to 30 kt. Chance SHRA.

Thursday: VFR. Windy with areas of gusts up to 30 kt. Chance SHRA, slight chance TSRA.

Thursday Night: Mainly VFR, with local IFR possible. Breezy. Slight chance SHRA.

Friday through Saturday: VFR.

MARINE

Forecaster Confidence Levels...

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

Through Tuesday night: High confidence.

Seas will continue to decrease to less than 3 ft through at least Tuesday night. W/SW winds 8-12kts today become W/NW tonight.

Outlook /Wednesday through Saturday/...

Wednesday: Winds less than 25 kt.

Wednesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Local rough seas. Chance of rain showers.

Thursday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 9 ft. Slight chance of rain showers.

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

Friday: Winds less than 25 kt. Seas up to 5 ft.

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

Saturday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ007- 014-015-019-022>024. RI...None. MARINE...None.