Immediately past the start/finish line is a channel through the rocks that allows you to cut across and miss the first left hand turn. A mask obviously makes this faster, so the snow will not slow you down.

At the first frozen lake, power slide left and jump over ravine. You will land just past tunnel bridge. A mask helps here, but is not necessary.

After making the right hand turn after the tunnel bridge, look on your left. There is a channel through the rocks that cuts across the left hand curve. With a mask, you can hit the hill on the right side of the passage and jump the guardrail to cut across.