textproduct: Boston / Norton

WHAT HAS CHANGED

No significant forecast changes.

KEY MESSAGES

- Dry conditions and low humidity continue through tonight leading to another pleasant day.

- Diurnal thunderstorms possible Wednesday through Friday, with above normal temperatures peaking on Friday.

- Temperatures remain warm, but humidity decreases, throughout the weekend, while uncertainty remains high regarding potential for rain showers.

DISCUSSION

KEY MESSAGE 1...Dry conditions and low humidity continue through tonight leading to another pleasant day.

The high pressure system sitting south of Long Island will continue to slowly meander further south throughout today, allowing for the continuation of dry conditions and mostly clear skies. Temperatures will continue to warm over the next week, aided by southwesterly flow, bringing today's high temperatures well into the 80s, with the exception of the immediate south coast, Cape, and Islands, where temperatures should remain in the low to mid 70s. Dewpoints will remain generally below 55, so humidity levels will remain quite comfortable despite the warm temperatures.

KEY MESSAGE 2...Diurnal thunderstorms possible Wednesday through Friday, with above normal temperatures peaking on Friday.

As the high pressure system moves south, dew points will surge generally in the mid to upper 60s... possible to near 70 degrees in some areas. While the combination of heat and humidity will create enough instability for elevated chances for the development of scattered showers and thunderstorms, several weak disturbances moving through the upper atmosphere could help trigger this activity, particularly during the afternoon and evening hours.

There remains little indication of a widespread severe weather event at this time. Guidance continues to indicate a possible weak warm front, somewhat limited instability, and weaker wind shear on Friday. Even so, a few stronger storms cannot be ruled out. The latest CSU machine-learning guidance continues to indicate 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.

Confidence is slowly increasing that heat and humidity could pose a risk, especially Thursday and Friday 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.

KEY MESSAGE 3...Temperatures remain warm, but humidity decreases, throughout the weekend, while uncertainty remains high regarding potential for rain showers.

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. Some ensemble guidance is even indicating a quick low spinning up over southern New England Saturday or Sunday, which introduces the potential for some spotty rain showers. Regardless, temperatures will remain quite warm, but dew points should fall back into the 50s, resulting in noticeably more comfortable conditions.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

Forecaster Confidence Levels...

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

18z TAF Update...High confidence.

VFR conditions continue into much of Wednesday. Some MVFR to localized IFR conditions may overspread parts of the region from southwest to northeast by early evening Wednesday along with a few showers. Showers become more likely Wednesday night, but coverage is still relatively uncertain.

Gusts will diminish this evening, but may linger a bit longer near the upper Cape/Buzzards Bay area. For Wednesday, gusts to around 20 kt may make a return by the mid/late morning hours. SW winds will persist through tonight and into Wednesday before shifting more S Wednesday night in the wake of a passing warm front.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Wednesday Night through Sunday/...

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

Thursday: VFR. Chance SHRA, slight chance TSRA.

Thursday Night through Friday: Mainly VFR, with local MVFR possible. Slight chance SHRA, slight chance TSRA.

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

Saturday: 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.

Through Wednesday Morning...High confidence.

High pressure centered across the mid-Atlantic states will continue to slowly sink southward through Tuesday night, with winds already shifting SW. Good mixing over the land should yield SW wind gusts around 25 knots across our nearshore southern waters Tuesday afternoon, prompting the continuation of Small Craft Advisories. The rest of the region should generally remain below small craft advisory criteria through Wednesday morning.

Outlook /Wednesday Night through Sunday/...

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. Local rough seas. Slight chance of rain showers, slight chance of thunderstorms.

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

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

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

BOX WATCHES/WARNINGS/ADVISORIES

CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 7 PM EDT this evening for ANZ231>236.