Storms to erupt along 1,200-mile-long corridor from nation's heartland to the Northeast

An eruption of severe weather targeted the northern Plains on Tuesday, and thunderstorm dangers persisted across parts of the Upper Midwest and eastern Great Lakes into Tuesday night. As the volatile pattern continues along the northern rim of building heat at midweek, more thunderstorms, some severe, will threaten a 1,200-mile-long corridor from the central Plains to the mid-Atlantic.

The greatest risk for thunderstorms will span across a narrow zone from portions of eastern Kansas to northern Delaware, eastern Pennsylvania, New Jersey and eastern coastal New York state into Wednesday night.

Nearly 45 million people could lie in the path of potentially damaging thunderstorms at midweek, and communities from Kansas City and St. Louis, Missouri, to Peoria, Illinois; Indianapolis; Columbus, Ohio; Pittsburgh; Philadelphia; Atlantic City, New Jersey; Baltimore and New York City are at risk.

"Even though a major outbreak of severe weather is not anticipated, some communities can be hit hard with damaging wind gusts and hail as well as torrential downpours that can lead to flash flooding," AccuWeather Meteorologist Issac Longley said.

In the most intense storms with strong wind gusts, an AccuWeather Local StormMax™ of 85 mph could occur, which is strong enough to knock over large trees, cause property damage and send trash cans and recycling bins sailing through neighborhoods.

A thunderstorm at Reading, Pennsylvania, produced a wind gust to 83 mph during the midday hours on Wednesday. A gust to 68 mph was recorded at Northeast Philadelphia Airport. The winds in these areas and others in Pennsylvania have knocked down dozens of trees and caused sporadic power outages.

As is the case with any thunderstorm, lightning can strike without notice. With some of the more intense thunderstorms, frequent cloud-to-ground lightning strikes can occur. And, a small number of the strongest thunderstorms will be capable of spawning a tornado.

Should the storms organize into a large complex, then the storm threat can extend farther to the south. Forecasters say portions of southern Indiana, Kentucky, southern West Virginia, southern and central Virginia, southeastern Maryland and southern Delaware could be hit with strong storms as well.

In rare cases, a powerful complex of thunderstorms can form and travel hundreds of miles with wind damage along the way in this type of weather setup.

"If a cluster of storms reaches specific criteria, and turns severe, triggering damaging, straight-line winds along a continuous 400-mile-long path or greater, it could even be classified as a derecho," according to AccuWeather Meteorologist Brett Rossio.

It appears the swath of damaging wind gusts extended for about 250 miles from northwestern Pennsylvania to the New Jersey coast on Wednesday.

The storms will focus along the northern edge of midsummerlike heat that has developed. Widespread high temperatures in the 80s and 90s are expected where the heat builds.

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Thunderstorms tend to form along a weak spot in building masses of hot air, which typically occurs on the northern periphery during this time of year. A factor that will make the storms more robust, in addition to heating of the day, is a push of slightly cooler air from Canada that sliced from the northern Plains to the Upper Midwest on Wednesday and will do the same over the northern tier of the Northeast on Thursday.

On Thursday, the dome of heat will shuffle farther to the west as a wedge of slightly cooler air becomes re-established in the Northeast states.

The cool air squashing the heat is likely to cause the swath of showers and thunderstorms to shift somewhat on Thursday.

A pocket of severe thunderstorms is forecast for southern Pennsylvania, Maryland, Delaware, West Virginia, eastern Kentucky and northern and western Virginia on Thursday.

Another pocket of severe thunderstorms is in store for parts of the central and northern Plains on Thursday.

In between, heavy, gusty and isolated severe storms are likely from the middle Mississippi Valley to parts of the Ohio Valley.

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