More than 1,000 flights have been canceled across the US as the Eastern seaboard and nearly 120million Americans are battered by severe thunderstorms on Monday.The storm system is heading east after walloping the Ohio River Valley Sunday, bringing potentially severe weather to areas east of the Mississippi River and will likely include high winds and large hail in addition to downpours and even possible tornadoes.The worst hit areas will likely be in the mid-Atlantic region, including southern Pennsylvania and New Jersey, Baltimore, New York, and Washington, DC