If it occurs within this universe, it is natural and can be traced; there is a reason for almost everything. I only say "almost everything" because someone will probably feel like bringing up quantum whatsitdonuts, and I don't feel like arguing the point.
Trouble is the quantum is the underlying basis of everything.
Everything is made up of quantum particles which obey incomprehensible quantum rules.
The sun wouldn't shine if it weren't for quantum indeterminacy.
So that's about everything you're trying to shove under the carpet.
Either way, if anything happens within this universe, there is a reason, even if that reason may exist outside of the universe. Nothing is, in the end, unexplainable; though it may be very difficult to trace.
So explain the quantum which is the underlying basis of everything we see and the reason for the light by which we see.
Supernatural, to me, is an Argument from Ignorance; you cannot explain it, therefore it is unnatural. It reminds me of those that see edited photos and film of "ghosts", and then proclaim it a supernatural phenomenon. They are ignorant as to the photographic editing or film editing; thus, they label it supernatural. (That probably wasn't the best example, but I can't think of a better one).
You're saying the quantum is supernatural?