A morning forecast can tell you if conditions will be ripe for thunderstorms in the late afternoon but those forecasts are not good enough to tell you exactly when and where the severe weather will occur.

Lots of times thunderstorms will be predicted but it will be perfectly clear for the ride home so I don't use those morning predictions to determine whether I will ride or not. Usually thunderstorms are pretty fast moving so as others have said, you can often find a safe window by either leaving a little early or staying a little late.