Let's start with the threat in the East. That threat is caused by the remains of tropical storm Bill, an unusually tenacious storm. It has been spinning small tornadoes since it came on shore.
The Mississippi Valley threat is the more serious. In addition to tornadoes, there is an enhanced risk of damaging winds and large hail. Residents of this area really need to keep an eye on the situation.
I will update the situation at least once this afternoon.