With a blind, you can still declare the attack, and with a disarm, you can't.
If
,
, or
(via his R, her W, or her R, respectively) disarms a target with an empowered auto like
's Siphoning Strike or
's Tumble, they cannot trigger the empowered attack at all, but keep the attack's buff and are allowed to trigger it when the disarm ends.
However, if
blinds either of these champions, they can trigger the empowered attack which will consume it, losing the buff that grants the empowered auto. However, because of the blind, the empowered attack does no damage and does not apply any secondary effects.