Tornadoes are forecast across the South today. Here's a look at the 10 deadliest tornadoes in U.S. history, according to the NOAA.
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Ed Zurga / Reuters
7. Joplin, Mo. (2011) -- The twister leveled homes and businesses and killed 161* people. *CNN and other news outlets have listed the death toll at 161; NOAA lists the toll at 158.