A rare super-outbreak of violent tornadoes occurred December 10, 2021. There were two primary tornado "lines". One stretched from eastern Missouri to east-central Illinois while a second began in northeast Arkansas and reached southwest Kentucky. The second line featured (potentially) the longest path of one tornado on record. The violent weather was caused by interaction with the East Pacific tropics, Gulf of Mexico and cold snow-covered areas to the north and enhanced by a vigorous jet stream and low-level jet out of the western Gulf.