Today is one of those forecasts where the atmosphere has the ingredients for severe weather, but we’re still waiting to see if they can all come together at the same time.

A warm front lifting north through southern New England will determine whether we can tap into warmer, more unstable air this afternoon. If that happens, thunderstorms will have a much better chance to intensify. If clouds and showers linger longer than expected, the severe threat would be significantly reduced.

The strongest activity – for now should remain through much of Vermont, and gradually weaken as they exit the Connecticut River Valley. A rare tornado watch was issued for all of New Hampshire and Vermont and parts of Massachusetts, Maine and Connecticut.

It was later canceled for Vermont and Massachusetts.

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We’re also paying closer attention to the wind energy in the atmosphere. Wind shear values are unusually strong for southern New England, with enough support for damaging wind gusts and even a brief tornado if storms can develop and organize. The limiting factor remains instability. Dew points aren’t that outstanding, but on a day like today, sun isn’t our friend. It’s what adds additional heat and energy for storms to fire.

There are some cases where exceptional wind shear has compensated for limited instability and produced severe weather.

The bottom line: today’s severe weather threat is conditional, but it’s not one to ignore. Confidence is low that widespread severe weather develops, but confidence is high that any storm that does form could become strong quickly. The greatest concern is from Vermont and into western Massachusetts and western Connecticut. We expect storms to form as a line during the mid-afternoon through early evening before the threat shifts east.

A straight-line wind event could unfold – where strong 45 mph winds blow across the Merrimack Valley mid-afternoon.

Stay weather-aware between noon and 9 p.m., especially if we see breaks of sunshine emerge during the afternoon.

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