There's so much wrong from a tornado point of view in that scene: 1) When you live in tornado country you know when the conditions are right for a tornado and you're not out driving on the highway so the 35 cars full of people are wrong right off. People tend to stick very close to home when there's a tornado watch on. On top of that, unless there's a football game that afternoon or church that morning, you don't find that many cars trailing each other on a minor highway between small towns in Kansas. 2) When you live in tornado country, you know that if you are in a car and a tornado is coming, you don't huddle under an overpass, you hit the nearest ditch and get down. Because of the way highways are built in that area, there are generally generous ditches on either side of the highway. If there's no ditch, then you find whatever divot in the earth you can - but you couldn't have Clark watching in anguish if he's head down in a ditch. The scene is contrived from start to finish to create the circumstances of Jonathon's death. It's clumsy for sure.