 A strong low-pressure area over the central Great Lakes and its associated cold front combined with intense wind shear to provide a favorable environment for supercell development.Despite only moderate instability (which meant only a slight risk of severe weather was issued by the Storm Prediction Center, and only modest probabilities for severe weather at first), supercells developed throughout the day over much of the central US and continued throughout the evening and overnight hours, continuing into the morning of January 8.The hardest-hit area was in the Ozarks, around Springfield, Missouri, where nearly continuous supercells developed throughout the evening, resulting in numerous tornado touchdowns.