Here is a picture of the the exhausts for my two furnaces. The exhausts face outward, and the intakes point downward. I am in central NJ and last winter the temperature went below zero for the first time in many years. I had no problems with water freezing in the elbows.

Are the PVC pipes must be pitched back towards the furnace? How far above the ground are the openings? You want to be higher than any snow accumulation. My exhaust is at 3 feet which is more than enough clearance.

Nice separation, Mike. I guess the exhaust air is hot enough to keep the moisture from freezing before it hits the cold air. My exhaust vent (left one in pic) is only about 8" off the ground - way too low. Haven't yet had snow cover it but I do get a fat icicle growing up from the ground beneath it. So I want to extend it UP by a foot and then over to the left by another foot or so. Kind of like your set up but lower.