Over 50 million people are at risk of severe weather

Over 50 million people are at risk of severe weather Thursday, from the central Gulf Coast through the Ohio River Valley, while a "tornado outbreak" is expected across the South.

The Storm Prediction Center says there's a high chance of tornadoes -- a level 5 out of 5 -- for parts of the South. That's the worst and highest forecast outlook issued for severe storms. And while it's very rare for the SPC to issue this kind of outlook -- it's now the second time in a week for the South.

the SPC warns of "several long-track tornadoes, destructive winds and very large hail forecast from the Lower Mississippi Valley, eastward across parts of the southeast and northward into the Tennessee and Ohio Valleys. "Some of the widespread winds will be "hurricane force," the SPC said, while some areas can seehail that is "baseball size."

Long-track tornadoes are tornadoes that are on the ground for an extended period of time. The majority of tornadoes are on the ground for just minutes, but with some severe events, there can be tornadoes on the ground for hours. This kind of tornado is known for causing widespread damage.