textproduct: Boston / Norton

WHAT HAS CHANGED

No significant forecast changes.

KEY MESSAGES

- Pleasant weather continues on Tuesday with mostly sunny skies but warmer high temperatures well into the 80s.

- Summer like heat remains in place through the weekend with changes for diurnal thunderstorms Wednesday through Friday.

DISCUSSION

KEY MESSAGE 1...Pleasant weather continues on Tuesday with mostly sunny skies but warmer high temperatures well into the 80s.

High pressure just off the mid-Atlantic coast will continue to slowly sink further south through Tuesday night. This will result in the continuation of dry and pleasant weather on Tuesday...but with warmer temperatures.

Mainly clear skies with light/calm winds tonight will result in good radiational cooling conditions and comfortable temperatures. Low temps tonight will range from the upper 40s in the normally coolest outlying locations...to the lower to middle 50s in most other locations. The mild spot will be the urban heat island of Boston with lows only dropping to near 60 as southwest winds begin to mix milder temps aloft.

Plenty of sunshine on Tuesday with a warmer southwest flow of air working into the region. This should push high temps well into the 80s in most locations...except 70s near the immediate south coast with a modified marine airmass given gusty SW winds. Otherwise...dewpoints will be low on Tuesday so humidity levels will remain quite comfortable despite the warm temperatures.

Dry and pleasant weather continues Tuesday night with low temps mainly in the middle 50s to the lower 60s.

KEY MESSAGE 2...Summer like heat remains in place through the weekend with changes for diurnal thunderstorms Wednesday through Friday.

High pressure positioned off the East Coast will continue to support a stretch of warm, summer-like weather across southern New England from Wednesday through the weekend. Temperatures several thousand feet above the surface will remain quite warm, favoring afternoon highs ranging from the mid 80s to lower 90s each day. Coastal locations will be cooler given the proximity to the ocean.

In addition to the warmth, a humid air mass will remain in place from Wednesday through Friday, with dew points generally in the mid to upper 60s and locally near 70 degrees. This combination of heat and humidity will create enough instability for scattered afternoon showers and thunderstorms to develop. Several weak disturbances moving through the flow aloft may help trigger this activity, particularly during the afternoon and evening hours.

At this time, there are no strong indications of a widespread severe weather event. The ingredients typically associated with organized severe thunderstormsincluding strong forcing, abundant instability, and stronger wind shear appear somewhat limited. That said, a few stronger storms cannot be ruled out. Current CSU machine-learning guidance indicates a 5 to 15 percent probability of severe weather Thursday into Friday, with slightly higher probabilities of 15 to 30 percent across portions of Connecticut. Forecast confidence regarding thunderstorm coverage and intensity should improve as higher-resolution guidance becomes available over the next couple of days.

Heat and humidity will also pose a risk, especially on Thursday when heat index values may approach 100 degrees in parts of the Connecticut River Valley. These values are associated with moderate to major heat impacts, increasing the risk of heat-related illness for anyone spending extended time outdoors without adequate hydration or access to cooling. Confidence remains too low at this time to determine whether heat headlines will be needed, but they may become necessary if confidence increases in heat index values exceeding 100 degrees.

By the weekend, a mid-level ridge is expected to strengthen over southern New England, promoting rising heights aloft and a somewhat drier air mass. While temperatures will remain quite warm, dew points should fall back into the 50s, resulting in noticeably more comfortable conditions and a reduced risk of afternoon thunderstorms.

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...

Tonight through Tuesday night...High confidence.

VFR conditions continue through Tuesday night. Winds shift to a SW direction with some 20-25 knot gusts during the day Tuesday...strongest of which towards the south coast and upper Cape.

KBOS Terminal...High confidence. Sea breeze should depart between 23z and 01z.

KBDL Terminal...High confidence.

Outlook /Wednesday through Saturday/...

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

Wednesday Night: Mainly VFR, with areas IFR possible. Breezy. SHRA likely, slight chance TSRA.

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

Thursday Night: Mainly VFR, with local MVFR possible. Chance SHRA.

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

Friday Night: VFR. Chance SHRA, slight chance TSRA.

Saturday: VFR. Slight chance SHRA.

MARINE

Forecaster Confidence Levels...

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

Tonight through Tuesday night...High confidence.

High pressure centered across the mid-Atlantic states will continue to slowly sink southward through Tuesday night. This will shift the winds to a SW direction tonight. Good mixing over the land should yield SW wind gusts around 25 knots across our nearshore southern waters Tuesday afternoon. Therefore...we have hoisted small craft headlines for these locations. The rest of the region should generally remain below small craft advisory criteria through Tuesday night.

Outlook /Wednesday through Saturday/...

Wednesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Seas up to 5 ft. Chance of rain showers.

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

Thursday: Winds less than 25 kt. Areas of rough seas. Chance of rain showers.

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

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

Friday Night through Saturday: Winds less than 25 kt. Slight chance of rain showers.

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...High Risk for Rip Currents until 10 PM EDT this evening for MAZ022- 024. RI...None. MARINE...Small Craft Advisory from 10 AM to 7 PM EDT Tuesday for ANZ231>236.