"I'm not a scientist but turbulence is simply changes in air. The changes can be caused by mountains, changes in temperature and storms.

Out of my years of flying, I've never experienced severe turbulence because pilots know where it is most of the time. Not only do they know where it is, but planes also talk to each other.

So if there is a pocket of unexpected turbulence, the planes in front of you will radio either air traffic control or the planes behind them and let them know they might want to change their altitude or go left or right"