Heat dome to break down as downpours, thunderstorms erupt

The clock is ticking on the extremely high temperatures from the Midwest to the Northeast, and as the heat dome weakens during the second half of this week, thunderstorms will erupt in areas where humidity levels remain high, AccuWeather meteorologists advise. In some cases in the Northeast, the cooldown can be dramatic.

Millions recently hoped for relief from the relentless downpours and abnormally cool conditions and they got their wish with a virtually cloudless sky and searing summer heat. Now, millions are seeking some relief from the sudden surge of extreme heat and blazing sunshine, or at least a break from the extreme temperatures.

Temperatures will throttle back as showers, thunderstorms return

In many cases, where high temperatures were within a few degrees of 100 F into Tuesday, highs closer to 90 will be in store later in the week, with some spots experiencing highs in the 80s. Where highs were in the middle to upper 90s during the first few days of the week, highs in the 80s will be more common by week's end, with some places getting a day or two with highs in the 70s.

"There's even a rare backdoor cool front that will drop southward from New England to part of the mid-Atlantic region during the middle and latter part of this week," AccuWeather Senior Meteorologist Brett Anderson said. "This can dramatically drop temperatures by 20-40 degrees in some cases, which is about as big as it gets this time of the year."

For example, in Boston, following highs near 100 on Tuesday, temperatures may be no higher than the 60s Thursday and Friday behind the front.

It will likely be a similar story in New York City, highs around the century mark Tuesday will be followed by highs in the 70s Thursday and Friday.

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For those fearing more weather whiplash, the return of thunder and downpours should be less extreme than before, in most cases. This is not to say that flash flooding will be absent everywhere, as that risk tends to accompany summertime thunderstorms.

The massive heat dome will slowly shrink and weaken

At first, the extreme heat will settle southward, but the mechanisms for producing the extreme temperatures will gradually disappear, allowing more typical summertime heat to take over.

As the heat dome weakens, thunderstorms will have an easier time erupting throughout the central and eastern United States. A complete pattern flip is likely to evolve in the Southeast as a ripple in the jet stream develops and lingers, leading to an eruption of showers and thunderstorms on a daily basis in some locations.

The boundary of the heat dome will shrink from the north and west, and the fringe zones likely will experience more cloud cover and more frequent shower and thunderstorm activity compared to the rest of the decaying heat dome.

This also means that some of the areas on the rim of the heat dome that were getting clobbered by daily storms should get a break from the downpours and severe weather.