The route described here ascends south, but another route goes north down a road/trail (actually part of the Great Western Trail).
From the parking area, cross the highway and start skiing up the righthand (west) side of the canyon. You might find, as I did, other ski tracks to follow. The route follows a summer trail route, which I recommend you follow in order to make it through some thick patches of scrub oak. The route stays on this same side of the canyon all the way to the new highway coming down the other side of Snow Basin Ski Resort. This new highway is not marked on older maps (which I had), but I'd guess it's probably about 2 miles from the trailhead, or about 1 1/2 hours.
For more info on trails in the area, contact the U.S. Forest Service at (801)625-5306.