There are two ways to use "au cas où", very much like in English:

(1) I told you, just in case. -- Je te l'ai dit, juste au cas où. There is no conditional here.

(2) In case you are late, come see me. -- Au cas où vous seriez en retard, venez me voir. In this case there is a conditional, since au cas où isn't by itself any more.