I am currently at the end of my wits. No matter what change I do to the North American geography, northeastern Nebraska (42.4649° North, 96.4131° West), is still in the danger zone called Tornado Alley. (Heaven forbid, I've had more than enough experience with that reaper's scythe in my lifetime.)
Changing the Rocky Mountains didn't seem to help, despite increasing their maximum height from 14,440 feet above sea level to 20,308 feet, resulting in a plateau that should have been tall enough to block off one of the three types of air crucial in creating the Alley--warm, dry air from the Southwest.
Changing the Great Lakes or the Appalachians didn't seem to help, either because they don't directly influence the Midwest's weather patterns.
So what DO I need to change to put northeastern Nebraska OUTSIDE the Alley while at the same time retaining the Midwest's prairie fertility and hope of having a White Christmas?