The owner of Black Bar Lodge set they were recent tracks and had been covered with recent snow. He could still see the indents. Remember they were driving in heavy snow at the time and it continued to snow.
I think in that type of environment it would be very easy to see even with large amounts of snow...you will still have the original indentations that would be covered and would dip down.
These guys can spot bear tracks and foot prints from helicopters I think tire tracks would be much easier to see while on the ground.
Oh, I didn't have the impression there was snow on the ground at all when they were on that part of the road.
I thought they didn't hit snow until much higher up, so they came back down and *then* it started to snow. Then it snowed and rained for two days after they had gotten stuck from the snowstorm that hit them that first night (the first Saturday, 11/25).