As the sun goes down and the air cools a little near the surface, the winds above the ground are not as affected as much by friction, and storms sometimes intensify (especially near boundaries) at sunset. This is something we have been researching at UAH, and it is happening tonight, with severe storms in NW and NE Alabama, and more likely to form.
Take a look at the thermal boundary.
The temperature goes from 80 near Tuscaloosa to the 50s in NE Alabama. Any storms near that boundary will have enhanced rotation potential, since the boundary provides extra spin horizontally in the atmosphere (warm air rises, cool air sinks) that storms tilt into the vertical (like a football tipped at the line of scrimmage).
This event is not over at all. Keep a source of weather information handy through the evening.
