This is perhaps the easiest route up “Ptarmigan Flat Top”. A good trail is followed up Mandall Creek to near Black Mandall Lake. From there an indistinct trail is followed to Mandall Pass followed by an mostly easy cross country hike to the summit.
This route is 11 miles round trip with about 2500 feet elevation gain.
From Yampa, look for the sign on the west side of Highway 131 that points the way to "National Forest Access". Turn west on to County Road 7. Follow County Road 7 for seven miles, to where the road becomes FR 900. The parking lot is 12.7 miles from Yampa (the junction at Antler’s Inn) and is just beyond the Bear Lake Campground.
Campsite alond Mandall Creek, not that far from the trailhead.
From the trailhead, follow the well marked trail to the northeast. Part of the trail has been rerouted and is in a different location than shown on the topo maps. It has more elevation gain than the old trail and climbs over a hill and past a pond before descending down to Mandall Creek. Once at the creek the trail follows the creek at a gentle grade into the upper basin.
After about four miles, the trail reaches a trail junction with the trail to Black Mandall Lake. Although the main trail continues left, much more traffic heads right and to Black Mandall Lake.
Stay left and follow the faded trail through the meadows to the base of the pass. The trail is marked by poles and cairns and is hard to follow in places. Aim for the right side of a small knoll below the pass. The real trail is here and the false trail on the left side of the knoll is tedious and unpleasant.
See the photo diagram. Stay away from the “X” area:
Mandall Pass is reached after about five miles from the trailhead. Ptarmigan Flat Top is not far to the southwest. Climb the faded trail and cross country route southwest to the plateau top. Once on the plateau top, head west to the highest point, which is marked with a cairn. It really is flat up there and several other points look higher, but if you wander around to them you will find that this is really the highest point. Enjoy the huge expanse of tundra before heading back the same way.
Ptarmigan Flat Top from Mandall Pass. The route to the summit goes up the grassy slopes to the right before crossing the vast tundra fields to the summit.
A good pair of boots is needed.