• MILWAUKEE (AP) -- The National Weather Service was tracking a so-called derecho weather pattern in the Midwest on Tuesday that could spawn severe windstorms in major metropolitan areas with gusts as strong as 100 mph.
• Derecho windstorms occur once every year or two across the central and northeastern U.S. in a band from Texas to New England. They pack hazardous winds of at least 75 mph or more and maintain their intensity for hours as they sweep across vast distances.
• In some cases a derecho will spawn tornados and accompany storms that produce hail the size of golf balls.
• The current pattern could affect larger metropolitan areas in Milwaukee, Chicago, Detroit, Cleveland and Pittsburgh in the next two days, said Bill Bunting, a meteorologist in the agency's storm prediction center in Norman, Okla.
• "We tend to be careful using the D word, but yes, a derecho is possible," Bunting said.
• The weather service was predicting a chance of storm activity beginning in southern Montana and northeastern Wyoming on Tuesday afternoon. It was expected to sweep eastward, with a 45 percent chance that severe wind activity would hit the southern half of South Dakota down to the northern ridge of Nebraska. There's a 30 percent likelihood the severe winds stretch into northern Iowa and southern Minnesota.
• "Thirty percent is pretty high in the world of predicting severe weather," said Paul Collar, a National Weather Service meteorologist in Sullivan, Wis. "All severe forms of weather will be on the table but with this pattern, strong damaging winds look to

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