A multi-day severe weather outbreak, which could be its most dangerous phase yet, could threaten parts of the Midwest, including much of Illinois, with potentially violent, EF3 or stronger tornadoes threatening nearly 40 million people across a zone from the Mississippi Valley into the lower Ohio Valley. The threat comes after days of severe weather across the Plains and South, producing over 50 tornado reports since Thursday. These include a violent EF-4 tornado in Enid, Oklahoma, deadly tornadoes in North Texas, and multiple Particularly Dangerous Situation tornado warnings. A Level 3 of 5 risk for severe thunderstorms is in place for Monday from parts of Mississippi Valley to the Ohio Valley, including Illinois, Missouri, western Indiana, western Kentucky and northwestern Tennessee. The corridor from central and southern Missouri into central Illinois may hold the most favorable environment for the strongest storms, though the precise location of the greatest tornado potential could depend on how morning thunderstorms shape the atmosphere ahead of the afternoon round.