Yeah absolutely. You can also submit to the jam then update the game with revisions after the jam has ended, if the project ends up being something you want to pursue in the future. Nothing is 'locked in' by submitting to the jam.
EDIT: I should clarify that you shouldn't upload unfinished games to the jam, then finish them later, but submitting a finished game, then going back to it later to improve it, add bits, etc. is fine.