textproduct: Boston / Norton

WHAT HAS CHANGED

No significant forecast changes.

KEY MESSAGES

- Pleasant, dry, and seasonable weather today with low humidity and abundant sunshine. - Increasing heat and humidity this week with afternoon thunderstorm chances Wednesday through Friday.

DISCUSSION

KEY MESSAGE 1...Pleasant, dry, and seasonable weather today with low humidity and abundant sunshine.

A really nice day is on tap for southern New England, featuring near- seasonable high temperatures, low humidity, and plenty of sunshine. With the departure of the mid-level trough toward the Canadian Maritimes and surface high pressure building in from the west, flow today will be from the north to north-northeast. Earlier in the day, the pressure gradient between these two systems will support breezy winds around 10 to 15 mph, with somewhat higher gusts along the immediate coast. As the pressure gradient relaxes, winds gradually shift toward the southeast before becoming south-southwest after sunset. High temperatures this afternoon will generally range from the 70s to near 80 degrees, warmest inland and away from the influence of the ocean. Coastal areas will mainly remain in the lower 70s, though cannot rule out a few upper 60s across the outer Cape and Islands.

With high pressure firmly overhead tonight and winds easing, conditions will favor radiational cooling. Temperatures fall into the 40s across many locations, while the urban core holds onto warmth with lows remaining in the middle 50s. Given the rainfall this past weekend, areas that decouple may experience patchy fog overnight.

KEY MESSAGE 2...Increasing heat and humidity this week with afternoon thunderstorm chances Wednesday through Friday.

Summerlike heat and humidity return this week as an anomalous mid- level ridge and surface high pressure expand into the region. Tuesday kicks off the warming trend, with 850 mb temperatures climbing into the middle to upper teens, supporting daily afternoon highs in the upper 80s to lower 90s. NWS HeatRisk guidance highlights the potential for heat impacts, with widespread moderate impacts and isolated pockets of major impacts, particularly across urban centers by late week. One possible fly in the ointment will be cloud cover and storm coverage during the middle to latter half of the week, which could keep temperatures just cool enough to avoid the need for heat-related headlines. Nevertheless, those who work outdoors should prepare for another stretch of unseasonably warm temperatures. Additionally, there will be little in the way of nighttime relief, with overnight lows generally remaining in the 60s.

As previously mentioned, cloud cover and storm chances increase during the middle to latter part of the week. By Wednesday, southern New England will reside near the base of the mid-level ridge with more zonal flow aloft. This pattern supports the potential for ribbons of mid-level energy traversing the CONUS, which could trigger scattered showers and thunderstorms within an increasingly warm, humid, and unstable airmass. Timing any thunderstorm remains difficult, as these details are often resolved on the mesoscale. However, there is moderate confidence in daily afternoon shower and thunderstorm chances Wednesday through Friday. Summerlike heat may persist into the upcoming weekend. FWIW, the hazardous weather outlook currently highlights portions of central and western southern New England for hazardous heat.

AVIATION /12Z MONDAY THROUGH FRIDAY/

Forecaster Confidence Levels...

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

12Z TAF Update:

Today...High confidence.

VFR and dry. NNE/NE winds to begin the day, eventually backing to the SW between 18-22Z from east to west.

Tonight...High confidence.

VFR and dry. SSW/SW winds 6 to 12 kt. Protected terminals, including KBED and KORE, may experience light to calm winds with patchy ground fog.

Tuesday...High confidence.

VFR and dry. WSW/SW winds 8 to 12 kt, with locally stronger gusts across coastal RI, southeast MA, Cape Cod, and the Islands, where gusts of 20 to 25 kt are possible.

KBOS Terminal...High confidence.

NNE/NE winds this morning become E to ESE this afternoon, then shift to the S/SSW by evening.

KBDL Terminal...High confidence.

Outlook /Tuesday Night through Friday/...

Tuesday Night: VFR. Breezy.

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

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

Thursday: VFR. Breezy. Chance SHRA, slight chance TSRA.

Thursday Night: VFR. Slight chance SHRA.

Friday: VFR. Slight chance SHRA, slight chance TSRA.

MARINE

Forecaster Confidence Levels...

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

Today through Tuesday...High confidence.

In the wake of a departing cold front, north-northeast wind gusts up to 25 kt will gradually subside this afternoon as high pressure builds in from the northwest and settles across the southern New England waters by Tuesday afternoon. This will lead to more tranquil boating conditions later this afternoon and again Tuesday.

Winds shift to the southwest Tuesday, though sufficient inland heating may lead to stronger nearshore wind gusts, mainly from Block Island Sound to Buzzards Bay and Vineyard Sound. Here, wind gusts may approach 20 to 25 kt and could warrant a short-duration Small Craft Advisory.

Otherwise, seas continue to subside today, ranging from 3 to 5 ft, with the roughest seas across the outer southeastern waters. Seas then diminish to 2 to 3 ft Tuesday, though localized 3 to 4 ft seas are possible in the aforementioned waters with the higher gusts.

Outlook /Tuesday Night through Friday/...

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

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft.

Wednesday Night: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers, chance of thunderstorms.

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

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents through this evening for MAZ022-024. RI...None. MARINE...Small Craft Advisory until 10 AM EDT this morning for ANZ231>235-237-250-251. Small Craft Advisory until 4 PM EDT this afternoon for ANZ254>256.