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Wild spring weather snarls parts of country

Ed Andrieski / AP

Two women share an umbrella to ward off snow as they walk the 16th Street Mall during the noon hour in Denver on Wednesday, April 17, 2013.

Severe thunderstorms, large hail and possible tornadoes menaced a swath of the country from northern Texas to St. Louis, Missouri, on Wednesday, while heavy rains in northern Illinois caused delays at Chicago-area airports and snow made for messy travel in Colorado.

The National Weather Service issued advisories of all types as harsh weather pelted the middle of the country throughout the day. 

Much of Oklahoma was under a tornado watch until late Wednesday as intense storms ravaged the Texas-Oklahoma border. That tornado watch extends north through St. Louis and central Illinois.

"There could be really strong storms later tonight, and that's always scary. That could be the case in central Oklahoma," said Carl Parker, a storm specialist for The Weather Channel.

A flash flood warning was in effect in northern Illinois, causing airport delays and cancellations. O'Hare International Airport reported delays averaging almost one hour, with more than 300 flight cancellations due to weather, according to the Chicago Department of Aviation.

At Chicago Midway International Airport, airlines were reporting some delays of 30 minutes or more, with a few flight cancellations.

Meanwhile out west, Colorado was still dealing with the lingering effects of heavy snowfall, which had created messy driving conditions. Multiple accidents Wednesday afternoon led the state's Department of Transportation to shutdown westbound traffic for a portion of Interstate 70.

Inbound flights to Denver International Airport were delayed an average of 2 hours 16 minutes Wednesday evening, according to tracking site FlightAware.com. Outbound flights were experiencing delays of about 45 minutes.

Areas around Denver were expected to receive 3 to 6 inches of new snow by the end of Wednesday.