Tim Houchin walks in the snow to work downtown, Tuesday, Feb. 1, 2011 in Tulsa, Oklahoma. Blizzard conditions struck the Tulsa area stranding motorists and shutting down much of the city. (AP Photo/Tulsa World, Christopher Smith)

Tim Houchin walks in the snow to work downtown, Tuesday, Feb. 1, 2011 in Tulsa, Oklahoma. Blizzard conditions struck the Tulsa area stranding motorists and shutting down much of the city. (AP Photo/Tulsa World, Christopher Smith)

Two U.S. Air Force Thunderbird pilots practice a maneuver during a rehearsal in preparation for a weekend air show in Oklahoma City, Friday, June 18, 2010. (AP Photo/Sue Ogrocki)

Two U.S. Air Force Thunderbird pilots practice a maneuver during a rehearsal in preparation for a weekend air show in Oklahoma City, Friday, June 18, 2010. (AP Photo/Sue Ogrocki)

The U.S. Air Force Thunderbirds practice a maneuver during a rehearsal in preparation for a weekend air show in Oklahoma City, Friday, June 18, 2010. (AP Photo/Sue Ogrocki)

The U.S. Air Force Thunderbirds practice a maneuver during a rehearsal in preparation for a weekend air show in Oklahoma City, Friday, June 18, 2010. (AP Photo/Sue Ogrocki)

Protestors wave signs outside a barricade at a local bookstore in Norman, Oklahoma, where former Alaska Gov. Sarah Palin is signing copies of her book, “Going Rogue,” Thursday, Dec. 3, 2009. (AP Photo/Sue Ogrocki)

Protestors wave signs outside a barricade at a local bookstore in Norman, Oklahoma, where former Alaska Gov. Sarah Palin is signing copies of her book, “Going Rogue,” Thursday, Dec. 3, 2009. (AP Photo/Sue Ogrocki)