A large, sloppy storm system brewing in the Midwest on Wednesday threatens to spawn thunderstorms with heavy rain, hail and even the chance for a rare, powerful derecho.
"We've got a couple of rough days from the Midwest over to the Mid-Atlantic area," said Tom Moore, meteorologist of The Weather Channel.
A derecho that struck last June caused 13 deaths and did $1 billion in damage. NBC's Mike Viqueira reports.
A derecho, a massive line of storms that spans 240 miles and brings straight-line winds of at least 58 mph, usually only hits the Midwest once a year. The phenomenon is difficult to forecast.
"It's like predicting a large tornado is going to happen," said MSNBC Meteorologist Bill Karins. "No one can do that. The only thing we can do is say conditions are favorable for one to happen.
"It's about as common as a really powerful tornado system, which we usually see about four or five times a year," he said.
Last June, a derecho with winds gusting close to 100 mph stretching from Illinois to Washington, D.C., killed 13 people, caused $1 billion in damage and left more than 4 million people without power, according to The Associated Press. An additional 47 people died as a result of downed trees and the ensuing heat wave that followed the massive storm.
More from NBC News: