So I went in search of the elusive "Polar Aspen Alley" along the Snowbowl Road. After seeing what looked like a couple of different options heading into the woods, but none that stood out as THE option, I decided to park and explore.
I followed what was a clearly used mountain biking trail leading off the paved road in the first turn below Snowbowl. This trail is obviously well maintained, as there were a couple of spots where bikers have built "ramps" which allow easy passage over more difficult terrain. I encountered a couple of folks on horseback while exploring the area.
I quickly figured out that there is a little maze of trails in this area, beginning at the first turn where I started, and moving downhill to the main roadside/trailhead parking area in the turn about half a mile down the road from there. All trails lead to the same old closed road however, and ultimately end up at the Alfa Fia Tank just below the aspen grove and out in the open Hart Prairie.
Just before leaving the aspens, the old road crosses the Arizona Trail, and the sign to the south indicates the trail is still under construction, while to the north it leaves the woods and heads across the open Hart Prairie toward the Aspen Nature Loop and the Snowbowl parking lot.
I plugged along some of the closed roads, and even discovered one open road. Strangely, the road still open to motor traffic seemed to be a very popular biking trail, which occasionally dipped into adjacent singletrack. I'd love to see if there's a Flagstaff biking club that has some kind of map of the trails around this area, because I encountered several well-maintained singletrack trails all over Hart Prairie, and even across the prairie, up to the Michelbach Ranch and Hochderffer Hills.
After looping around, I decided to explore a bit above the Snowbowl Road, and this area is much less visited. In fact, it was difficult to find the old road in places, while in others it was apparent where it used to be. Eventually I met up with the Kachina Trail, and headed back to the trailhead and back down to my truck, with lots of notes and marks on my map.
I've posted a map of my discoveries in my photoset. Hopefully it will help the next person who heads to this area to explore!