Severe storms, flooding downpours to ramp up in northeastern US prior to week's end

By Alex Sosnowski, AccuWeather senior meteorologist

After locally severe storms hammer the Appalachians and some of the northern and western suburbs of the major mid-Atlantic cities on Thursday, localized flooding downpours are forecast along the Interstate 95 corridor and coastal areas of the Northeast Thursday night and Friday.

As a storm system enters the hilly terrain of the Appalachians, combined with daytime heating and moist air, showers and thunderstorms will erupt on Thursday.

The main threats from the storms from eastern Tennessee and western North Carolina to northern New York state, Vermont and neighboring Canada will be strong wind gusts, flash flooding and frequent lightning strikes.

Cities at risk for severe weather and flash flooding during the day Thursday include Pittsburgh; Charleston, West Virginia; Buffalo, New York; and Knoxville, Tennessee.

Thursday afternoon and evening, the risk will shift a bit farther east. Among the cities that may be affected are Albany, New York; Burlington, Vermont; Harrisburg and Scranton, Pennsylvania; Washington, D.C.; and Roanoke, Virginia.

Washington, D.C., and Frederick, Maryland, were hit hard by flash flooding during Monday morning. Washington, D.C., received 3.30 inches of rain in an hour.

"During Thursday night, the intensity of the storms will diminish in terms of wind gusts," according to AccuWeather Senior Meteorologist Dave Dombek.

"However, a considerable threat will remain in terms of urban and small stream flooding from near I-95 to the immediate coast of the mid-Atlantic and New England," Dombek said.

The weather pattern has the potential to unleash rainfall on the order of 1-2 inches per hour and perhaps 3 inches per hour in extreme cases.

The downpours may persist in part of this busy travel swath into Friday. Motorists and airline passengers should anticipate delays.

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Dry air is forecast to filter southeastward across the Great Lakes region and into the central Appalachians on Friday. However, it may take until Saturday midday and afternoon before it turns a bit less humid in coastal areas of the mid-Atlantic and New England.

The change in air will result in slightly lower temperatures at night this weekend, but because the sun is intense at this time of the year, the afternoons this weekend will still be quite warm in the Appalachians and very warm to hot near the coast.

Much of next week will feel like the middle of the summer.

"We expect a heat wave to build in much of the Northeast during next week," according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.

"Exactly how hot it gets and for how long will depend on the movement of a budding tropical storm, currently in the Gulf of Mexico," Pastelok said.

Highs near or above 90 degrees Fahrenheit are likely to be common from the Ohio Valley to the mid-Atlantic and part of New England. At least a couple of days of hot weather are also likely in northern New England as well.

In some of the major I-95 cities, highs are likely to be in the middle 90s.

AccuWeather RealFeel® Temperatures are likely to be 10-15 degrees higher than the actual temperature from the late morning through the afternoon hours due to the amount of sunshine, building humidity and light winds anticipated.

Keep checking back for updates on AccuWeather.com and stay tuned to the AccuWeather Network on DirecTV, Frontier and Verizon Fios for the latest on the severe weather, heat and tropics.