Use the adverb patently when you want to emphasize something as clearly obvious. For example, you might say "It's patently clear that you hate spinach."
It might be patently obvious to you that your roommate forgot to take out the trash, or patently absurd that your brother thinks he will have a long, successful career as a street magician and fire juggler. Either way, the word patently serves to emphasize how apparent or clear your observation is. The Latin root of patently makes its meaning patently clear: patere means "lie open" or "be open."