Why the South gets more killer tornadoes at night

Forget "The Wizard of Oz." Tornadoes are causing far more deaths and destruction east and south of Kansas these days. And they're often doing it in the dark of night.

Tuesday night's deadly tornado that struck the New Orleans area is the ideal example of what experts say is the 21st century problem with twisters: Killer tornadoes have shifted a bit out of the vast emptiness of the Great Plains, more into the Southeast where there are more people to hit, poorer populations and more trees to obscure twisters from view.

And if that's not enough, these Southeast twisters are more likely to strike at night when they are more dangerous.