New rounds of severe thunderstorms are underway and life-threatening, potentially catastrophic, flooding risks are brewing in the central and eastern United States Tuesday, putting more than 50 million people at risk of dangerous weather this week.

At least one person has died in southwest Oklahoma after flash flooding hit the region, with authorities warning people to stay off the roads as severe weather warnings continue.

Severe storms are still underway on Tuesday morning in northern Texas and Oklahoma as golf ball-sized hail has already been reported early Tuesday in Oklahoma amid numerous severe thunderstorm warnings. Meanwhile, a severe thunderstorm watch has been issued for northern Oklahoma and southern Kansas until 10 a.m. CT.