I don't really see a use for this. Members can do this in Preferences:
Restore dismissed notices
Any notices you have previously dismissed will be restored to view if you check this option.
And if you, as admin, had say a seasonal announcement that was dismissible, you would just create a new one the next season. That, or make it non-dismissible. If the same exact notice I dismissed kept reappearing, I would not like that, as a user.