Can all ground Aoe like Morgana W show even if you can't see the enemy champion?

For instance, In a poro king, the enemy varus threw down his E, I could see the arrows, but the ground was invis, but it'd slow still. It'd be nice to see what you should still avoid in lingering effects like that or if we could make it so if Rumble ult did the same thing. Invis when not seeing champ.