Should I contact a potential PhD supervisor who strongly encouraged me to apply after not having heard from my application?
From my experiences in an engineering program at a public university, I've heard that domestic applicants are processed first. I don't think it would hurt to follow up with the potential supervisor. I agree with astronat above about sending a  polite email to follow up with the potential Ph.D. supervisor. You could also ask this professor when you can expect to hear back from the university.