Sidewall venting height requirements

American Standard gas furnace unit in the basement, venting out the sidewall of the house. Here in Illinois it snows sometimes. What are your thoughts on what the minimum height should be for the vent termination above grade? This one had 15" clearance. My thought is that is not enough. Anyone have any opinions?

Also it is right behind the AC unit and blowing furnace exhaust onto the AC unit.

I think I remember a minimum of 12" above expected high snow level…