textproduct: Boston / Norton

WHAT HAS CHANGED

Later frontal passage Friday brings increased shower and thunderstorm potential.

KEY MESSAGES

- A generally unsettled pattern persists through Friday as a quasi-stationary front remains across the Northeast, resulting in multiple opportunities for showers and thunderstorms. While coverage should remain limited through Thursday, stronger forcing Friday may bring a better chance for showers and thunderstorms before drier weather arrives for the weekend.

- Temperatures trend toward seasonable levels through the end of the week, with lower humidity and more comfortable conditions expected this weekend.

DISCUSSION

KEY MESSAGE 1...A generally unsettled pattern persists through Friday as a quasi-stationary front remains across the Northeast, resulting in multiple opportunities for showers and thunderstorms. While coverage should remain limited through Thursday, stronger forcing Friday may bring a better chance for showers and thunderstorms before drier weather arrives for the weekend.

A mid-level ridge remains anchored across the south-central and southeastern CONUS, while a weaker ridge extends into the Canadian Prairies. This leaves the flow aloft relatively quasi-zonal, allowing shortwave energy to quickly traverse the continent into the northeast. Given the lack of strong synoptic-scale forcing, shower development and coverage will remain difficult to pin down through Thursday.

Today will be mainly dry, with a weak surface low passing south of New England. The highest PoPs, generally 10-20 percent, will be confined to the immediate south coast and Islands during the morning. Otherwise, a mix of sun and clouds is expected, although another surge of wildfire smoke may result in hazy or milky skies. A mid-level shortwave trough will move through tonight into Thursday morning, providing enough forcing for scattered showers and a few thunderstorms. Coverage should remain limited, however, with PoPs generally in the 20-30 percent range northwest of I-95 and I-495. Thursday features a weak disturbance passing through the flow, with similar PoPs once again across the eastern half of southern New England.

A more notable change arrives Friday as the front's departure has trended later. A stronger 500 mb shortwave trough and increasing forcing will bring a better chance for showers and thunderstorms, particularly as the front finally pushes offshore. Behind the front, high pressure builds into the region for Saturday and Sunday, bringing a much drier airmass along with mostly sunny and comfortable conditions. The next opportunity for more substantial rainfall arrives late Sunday into Monday as low pressure approaches from the northern Great Lakes.

KEY MESSAGE 2...Temperatures trend toward seasonable levels through the end of the week, with lower humidity and more comfortable conditions expected this weekend.

Temperatures aloft gradually cool through the end of the week, with dew points following suit. The result will be a noticeably cooler and more refreshing airmass by late week. The weekend is shaping up to be the most comfortable stretch of weather in quite some time, with highs generally in the upper 70s across interior southern New England and lower 80s along the coastal plain. Dew points in the 50s will make for much more comfortable conditions, while overnight lows fall into the 50s Saturday and Sunday mornings. Temperatures early next week remain seasonable, though dew points may trend upward on Monday depending on the timing of the next frontal system.

AVIATION /14Z WEDNESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

18z TAF Update:

Today: High confidence.

VFR. North to northeast winds under 10 kt; sea breeze SE at BOS looks unlikely but will flip to S around 10 by by 00z.

Tonight: Moderate confidence.

VFR initially, but SHRA/embedded weak TS coming in from the NW after 03z. BKN/OVC VFR/MVFR ceilings with SHRA more likely for BDL, but have left as PROB30s for BOS, PVD and ORH. Winds become SW 5-10 kt.

Thursday...Moderate confidence.

Lower-end VFR to MVFR ceilings to start, improving to VFR (CIGs 050- 080) during the afternoon. SW to WSW winds around 10 kt.

KBOS Terminal...High confidence.

KBDL Terminal...High confidence.

Wildfire smoke aloft possible.

Outlook /Thursday Night through Sunday/...

Thursday Night: VFR. Slight chance SHRA.

Friday through Friday Night: VFR. Breezy.

Saturday through Saturday Night: VFR.

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

MARINE

Forecaster Confidence Levels...

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

Through Thursday...High confidence.

Today, localized sea breezes may develop near shore, while offshore winds remain SW to SSE at less than 10 kt. Somewhat stronger SW to SSW winds are expected Thursday, with gusts around 20 kt. Seas will remain below 3 ft throughout the forecast period.

Outlook /Thursday Night through Sunday/...

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

Friday: Winds less than 25 kt. Seas locally approaching 5 ft. Slight chance of rain showers.

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

Saturday Night through Sunday: Winds less than 25 kt.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...None.