textproduct: Boston / Norton

WHAT HAS CHANGED

Small Craft Advisory canceled.

KEY MESSAGES

- Mainly dry and seasonable conditions, outside of a stray shower this afternoon across the western half of southern New England.

- Main risk for a round of scattered showers and a few thunderstorms will be sometime late Thu/Thu night into Fri with summerlike humidity. Mainly dry and seasonable weather favored for this weekend.

DISCUSSION

KEY MESSAGE 1...Mainly dry and seasonable conditions, outside of a stray shower this afternoon across the western half of southern New England.

Southern New England will be stuck between a couple of synoptic features, leaving our weather somewhere in the middle as well. High pressure over the OH Valley and central Appalachians should mean plenty of dry hours today with a steady west to southwest wind. However, the subsidence from this high pressure will not be absolute.

A mid level cold pool over the Great Lakes and Ontario should generate some diurnal clouds heading into this afternoon, which will then diminish with sunset. The addition of a weak surface trough moving into southern New England could trigger a few showers this afternoon. Anticipating most unstable CAPE values between 500-750 J/kg this afternoon. Thus, cannot completely dismiss the idea for a thunderstorm or two. However, severe weather is not expected. The greatest risk for these showers will be across the western half of southern New England, away from the marine influence.

Dry weather is expected Wednesday.

As for temperatures, expect a seasonable week, with afternoon highs in the lower 80s and higher-terrain communities in the northern Worcester Hills and eastern Berkshires remaining in the middle to upper 70s. Nightly lows will be a touch cooler as clear skies and light winds allow for radiational cooling, with temperatures slipping back into the 50s while urban areas remain near 60 degrees. This setup may allow for another night of low stratus or fog. Confidence in how widespread it becomes remains low; however, it does not appear this round of fog will be as prevalent as last night.

KEY MESSAGE 2...Main risk for a round of scattered showers and a few thunderstorms will be sometime late Thu/Thu night into Fri with summerlike humidity. Mainly dry and seasonable weather favored for this weekend.

The next shortwave trough approaches from the west by late in the work week. Ahead of this approaching shortwave, summer-like humidity will return Thu into Fri. Timing quite uncertain this far out in the forecast. But appears there will be the potential for a round of scattered showers and a few thunderstorms sometime in the late Thu/Thu night into Fri time frame. CSU machine learning probs do indicate some low probs for severe weather/heavy rainfall potential. But that is really just climo for an approaching shortwave this time of year. So, not much more we can say at this point. Current guidance does indicate that drier/seasonable weather is favored to return for this upcoming weekend.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

18Z Update...

This afternoon...High confidence.

VFR. Mostly dry with a few spot showers during the afternoon. W winds 6-12 knots, except some 20+ knot gusts possible towards the upper Cape.

Tonight...High confidence.

VFR. Calm/Light WNW winds. Patchy fog possible.

Wednesday...High confidence.

VFR. Light west winds, with local seabreezes towards the coast.

Wednesday night...High confidence.

VFR. Winds light and variable. Patchy fog possible.

KBOS Terminal...High confidence in TAF.

We think pressure gradient remains just strong enough to result in mainly W winds today. However, the low probability exists for a few hours of sea breeze. This risk/duration too limited to insert into the TAF at this time.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday Night through Sunday/...

Wednesday Night: VFR.

Thursday: Mainly VFR, with local MVFR possible. Breezy. Chance SHRA, slight chance TSRA.

Thursday Night: Mainly VFR, with local IFR possible. Chance SHRA, slight chance TSRA.

Friday: VFR. Chance SHRA, chance TSRA.

Friday Night: Mainly VFR, with local MVFR possible. Slight chance SHRA.

Saturday: VFR.

MARINE

Forecaster Confidence Levels...

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

Through Wednesday night...High confidence.

Fairly quiet boating conditions through the first half of this week as high pressure develops across the Midwest before expanding toward the waters off the coast of southern New England. Gusty southwest flow develops today, with gusts around 20 kt. Conditions improve overnight into early Wednesday morning as winds shift to the northwest.

Outlook /Thursday through Sunday/...

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

Thursday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain showers, slight chance of thunderstorms.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight chance of rain showers.

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

BOX WATCHES/WARNINGS/ADVISORIES

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