Note that Alta owns (or leases?) the land that is the Grizzly Gulch area, so it behooves all of us to be good stewards of it to maintain access. We wouldn't want them expanding their ski resort into this area or closing it. Let's keep it free.
Begin at Alta's upper parking lot. There are 3 ways to get into Grizzly Gulch: 1) Michigan Road, 2) the summer trail (depicted on the map), and 3) going right up the gulch itself. This latter option puts you in a terrain trap, so it may be best only as a descent back to your car.
To get to the summer trail, follow the Albion Basin Road until you reach a left turn that cuts the huge switchback. This left turn is often marked by a sign and a cat-track. The sign will tell you if Alta has opened or closed access to Grizzly Gulch. Go up until you cross Albion Basin Road to cut another one of its switchbacks, and then cross Albion Basin Road again to find the summer trail. (Mind the private property.)
The summer trail is sometimes plowed through by a cat-track (all the way to the pass) as Alta sometimes takes people up there for cat skiing. Wind your way up and around, following the power lines, to get into the Grizzly Gulch area. The summer trail seems to present you with your first exposure to possible slide run-outs, but you're out of dodge once you begin climbing the west ridge of Patsy Marley
Follow this ridge all the way to the peak, being careful along the way to avoid cornices. Once at the peak, there are many options. Some ski the South Face of Patsy down to Albion Basin Road or the North Face to the pass. Both of these are well-known slide paths, but offer great skiing under stable conditions. If things don't feel right, ski back down the ridge the way you came. You can also continue down the east ridge to access Granny's Chute.
I toured this very route starting at 5:30 a.m., May 1, 2018, and it was a perfect powder day on the North Face of Patsy! Now if I could just learn to ski the pow...