Severe storms could break more than the heat in eastern US

Powerful and damaging thunderstorms that have been focused mostly on the Midwest in recent days will turn their attention to the eastern United States through midweek.

As a cold front gains momentum, severe thunderstorms, many packing high wind gusts, will erupt and roll from the eastern Great Lakes, Ohio Valley and middle Mississippi Valley to the Appalachians and Atlantic Seaboard into Wednesday and beyond in some cases, AccuWeather meteorologists warn.

The storms can trigger regional power outages and lead to major travel delays as they approach and pass through the major metro areas. Tree and property damage will be likely in some communities.

In recent days, severe storms have packed quite a wallop in the Midwest and part of the interior Northeast. During Monday night alone, hundreds of incidents of high winds and wind damage occurred from Iowa to Illinois and Indiana as a large complex of severe thunderstorms covered hundreds of miles and triggered at least one report of a tornado in the Chicago area.

AccuWeather meteorologists believe the complex met the National Weather Service definition of a derecho where there were consistent incidents of high wind gusts (58 mph or greater) over a distance of at least 400 miles. Close to 300,000 utility customers were without power from Iowa to Illinois and Indiana in the wake of the storms, according to poweroutage.us.

Even though conditions that produced the powerful thunderstorm complex are changing, it does not mean that storms cannot be severe at the local and regional levels.

"The front is pushing into a zone of very hot and very humid air so it would not take much to produce heavy and gusty thunderstorms at the very least in a number of locations," AccuWeather Chief On-Air Meteorologist Bernie Rayno said.

As the storms get a boost from daytime heating, some will turn severe and can produce high winds, frequent lightning strikes and brief torrential downpours from the St. Lawrence Valley to the central Plains and parts of the central Rockies Tuesday.

At this time, the most significant risk of a few tornadoes will extend across much of upstate New York to part of Vermont from Tuesday afternoon to Tuesday evening. The risk includes the upper part of the mid-Atlantic region, including the Washington, D.C., Philadelphia and New York City metro areas. Storms that fire up over the Ohio Valley are more likely to bring severe weather on a regional basis from Pittsburgh through Evansville, Indiana, and on into central and southern Missouri.

The AccuWeather Local StormMax™ wind gust for Tuesday's storms is 75 mph, which is Category 1 hurricane strength.

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"Because the thunderstorm downpours will occur in parts of the Northeast that were hit with flooding last week, enough rain will be released in parts of northeastern New York to Vermont and New Hampshire to lead to flash flooding of small streams and quick rises on some of the larger rivers," AccuWeather Meteorologist Brandon Buckingham said.

Brief urban flooding can occur in any metro area where downpours persist. Toronto received several hours of heavy rain and caused some city streets to look like rivers with multiple vehicles becoming swamped on Tuesday morning.

As the cold front continues to press on at midweek, so will the likelihood of severe thunderstorms.

Wednesday's severe weather threat is forecast to extend from New Brunswick southward to the Carolinas and northern Georgia, then westward to eastern portions of Kansas and Oklahoma. Where severe thunderstorms are anticipated in parts of the area, a moderate risk of severe weather will be centered along Interstate 95 from southern Maine to northern Virginia, as well as areas farther to the west in Virginia. A moderate risk means that numerous severe thunderstorms are likely to occur.

Similar to Tuesday, the main threats to lives and property will stem from powerful wind gusts and frequent lightning strikes. However, torrential downpours can also hinder travel.

The AccuWeather Local StormMax™ wind gust for Wednesday's storms is 75 mph.

On Thursday, the overall intensity of severe weather may be somewhat reduced to a more sporadic nature. However, there will be at least some risk of locally damaging thunderstorms packing high winds and torrential downpours centered not only on the Carolinas but also much of Georgia and central and southern Virginia.

Locally heavy and gusty thunderstorms may extend westward to parts of the lower Mississippi Valley as well Thursday.

As the storms settle over the Southeast states from Thursday into the weekend, where the cold front is forecast to stall, the incidents of flash flooding are likely to increase as beneficial rain in drought areas becomes more problematic.

"A general 1-3 inches of rain is likely to fall from late this week to early next week, AccuWeather Meteorologist Elizabeth Danco said, "But where those downpours persist, amounts may reach or exceed 6 inches during the period."

Some of the more intense downpours can bring rainfall rates of 1-2 inches per hour for a time, which is more than enough to lead to urban flooding problems.

Even in a pattern where downpours become the major problem for outdoor plans, some storms can pulse enough during the afternoon and early evening hours to trigger locally damaging wind gusts in the Southeastern states.

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