Humid Wednesday Weather Fuels Thursday Thunderstorms

Sprinkles will arrive by Wednesday evening, growing into showers overnight and finally scattered thunderstorms by Thursday afternoon

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Humidity is increasing across New England as we approach the end of summer warmth for the foreseeable future.

The new air has not only has been on the national weather map but also making headlines – from 17” of snow in Casper, Wyoming, to frost advisories and freeze warnings throughout the Rockies, the Northern Plains and into Minneapolis. The colder air is not quietly staking out its territory. 

A wind from the south, aided by a large dome of high pressure – fair weather – over the Western Atlantic, continues to pump warmth and now increasing humidity into New England, but this air will end up no match for the advancing cool air. 

For now, dew point temperatures are climbing steadily Wednesday and Thursday into the 60s, near 70. This will ensure a more humid feeling and overnight to bring early morning low-altitude clouds and fog. 

Higher in the sky, clouds are spilling over New England, meaning even after morning gray burned off Wednesday, we still are left with only limited sunshine, muted and dimmed by the new clouds aloft. By Wednesday evening, first sprinkles will arrive to the south coast. Those sprinkles will grow overnight into showers, then become scattered thunderstorms Thursday afternoon as a cold front slices into New England from the northwest. 

The cold front – a shift of wind on the leading edge to the cold air moving toward us – and associated thunderstorms may produce locally heavy downpours. The humid air will only help to fuel them, but that will clear the coast overnight Thursday. Early morning coastal clouds will likely linger Friday, but are set to give way to sunshine as new, dry air takes over.

The new air marks a distinct autumn feeling that won’t just burst into New England for Friday, but stays the length of our exclusive First Alert 10-day forecast. In fact, even as warm air tries to make a comeback Sunday, it will only collide with stubborn cool, creating a blossoming area of showers from west to east Sunday. 

The exact start time is still TBD on Sunday’s showers, but it’ll be an important factor because they are expected to last about 12 to 18 hours. Once they begin, the rest of the day will be wet. Right now, the most likely start time looks to be somewhere around a noon. As the fall feeling continues through next week, another shot of dry air will mean a quiet week of weather for New England, Monday to Friday.

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