AccuWeather.com

By Alex Sosnowski, Expert Senior Meteorologist

Jun 1, 2011; 11:06 PM ET

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"Cities at risk include the swath from Roanoke, Va. to Washington, D.C., Philadelphia, New York City, Boston and Portland."

Gusty and locally severe thunderstorms continue to sweep through the East today will break the heat wave, but may also have some damaging consequences. Two tornadoes have already ripped through western Massachusetts, killing 4 people.

***At 7:20 p.m. the supercell was headed toward Oxford.

***At 7 p.m. a tornado was on the ground south of Palmer, Mass. This tornado will continue eastward toward Fiskdale in western Worcester County.

***At 6:40 p.m. another tornado was reported north of Springfield in the vicinity of U.S. Route 20.

***At 6:15 p.m. Another supercell formed and was heading toward Springfield. The southern cell is now heading toward South Walpule and Foxborough., and a tornado was reported in Westfield.

***At 5:30 p.m. Cell was moving eastward through southern Worcester County, including Sturbridge and Oxford. Tornado reported near I-84 with cars overturned in Sturbridge.

***At 5 p.m. A supercell with a tornado was reported in Westfield, Mass. and this cell made its way to Springfield, where a tornado was also reported.

***At 4:30 p.m. radar showed a cluster of severe thunderstorms moving across western Massachusetts.

***At 3:30 p.m. radar indicated a debris ball near Bethel, Maine. A debris ball is indicative of a tornado on the ground. This storm is heading in the direction of Augusta, Maine.

***At 3:07 p.m. baseball-sized hail fell on Shaftsbury, Vt.

***2:45 p.m. EDT...Radar was indicating hook echoes and rotation in some of the storms in southern Vermont, southern New Hampshire and western Massachusetts.

Storm damage in Monon, Mass. taken by AccuWeather.com Facebook fan Bryan P.

Some areas may be hit by high wind gusts, frequent lighting strikes and large hail. A couple of the strongest storms from Virginia to Maine and neighboring Canada could produce tornadoes, especially from the lower Hudson Valley of New York to interior New England.

Slightly cooler air along the New England coast should weaken the storms slightly, while invading dry air on westerly winds may deprive storms of rotation over much of the mid-Atlantic.

Cities at risk include the swath from Roanoke, Va. to Washington, D.C., Philadelphia, New York City, Boston and Portland.

The storms are likely to be fast-moving and may sneak up on areas with little notice, so people should keep alert for rapidly changing weather conditions today.

The storms will bring the risk of downed trees and power lines, as well as travel delays and foiled outdoor activities.

It is possible that little or no rain falls in some areas. However, this does not mean that wind damage cannot occur.

In the wake of the storms, Thursday into the weekend will have conditions trending to less extreme levels, but temperatures will still average 5 to 8 degrees above normal.

While the atmosphere was very warm aloft over the Northeast Memorial Day, keeping thunderstorms from firing off during the afternoon and evening, changes will take place Wednesday, favoring not only thunderstorms, but also potential for severe weather.

Cooler air moving in aloft, combined with broiling heat at the surface, will lead to a volatile atmosphere from the Appalachians to the Atlantic Coast.

The frontal system producing the severe weather in the East today has had a history of wind damage and power outages in the Midwest.

Meteorologist Bill Deger contributed to the content of this story.