How does Sophocles use foreshadowing to hint at Oedipus's downfall in Oedipus Rex?

The question of foreshadowing in any Greek tragedy strikes
me as a little bit difficult to deal with because almost all of the audience would have
known the basic plot of the story before the play even began. Still, Sophocles leaves no
doubt in his play that Oedipus is going to fall and fall
hard.

For example, in the play's prologue, the Priest urges
Oedipus to take action regarding the plague unless he wants to be king "in
a desert" (Ian Johnston translation). I find in this statement some irony
because by the end of the play Oedipus will no longer be king of Thebes and he will have
to wander as an exile far from the society of his fellow human
beings.

Later, after learning from Creon that they must
expel Laius' killer from Thebes, Oedipus again ironically foreshadows his own demise as
he urges his fellow citizens, "Ban him from your
homes."

Likewise, in the same speech,
Oedipus ironically foreshadows what befalls him at the end of the play when he
unwittingly calls down upon himself the same curses that he invoked upon Laius' killers.
Oedipus says that even if the killer turned out to be an "honoured guest" in his own
home, he prays that he himself "suffer all those things I’ve just called
down upon the killers."

So, from the
beginning of the play, Sophocles leaves his audience numerous indications that things
will turn out badly for Oedipus.