Is this phenomenon called skipping? What causes such a large outbreak of
this, high clouds or something else? A very interesting evening, as it was
occurring on just about all of the center and approach frequencies that I
was monitoring.

Skipping, ducting, different places call it different things.
Solar radiation affects the ionosphere, causing the various layers to
rise or descend. Depending on the frequency and the ionosphere layer,
the radio signal will make a single bounce/reflect or may become
temporarily trapped between two layers and bounce/reflect off the top
and bottom before escaping some distance from the source.