From the Obsidian Trailhead on Highway 242 hike in the Obsidian Trail 3.4 miles crossing the Jerry Lava Field to the Sunshine camp. From there take the path to the left that leads to the PCT. Once at the PCT follow the climbers trail going straight ahead. This runs through a meadow with excellent views of both North and Middle Sisters. The meadow gives way to more rocky terrain and the trail gets harder to follow. About 7-10 minutes after the meadow, the trail will follow right next to a creek and then head sharply to the right up a 5-10 meter hill. At this point, you could do one of two things a)head across the creek to the left and do not follow the trail to the right (There is a small bridge of stones in the creek which point out where to make the crossing. Once across it is fairly easy to pick up the trail again) or b) (from SP member Vancouver Islander) head right and climb the 5-10 meter hill alongside the stream and then look for a crossing to the left (east). He reports this crossing is more obvious and leads to a good trail almost up to the glacier.
Follow the cairns if you can but basically, head towards the gap between North and Middle Sisters keeping Folding Rock on your right. It gets fairly steep here before you reach Collier Glacier.
Once on Collier Glacier (from the climbers trail that joins the glacier in the middle), depending on conditions, you may need crampons. The path is less steep towards the north side but it also could be pretty crevassed. You'll want to make your way eventually to the south side of the glacier (less steep on the top) until it ends in a point between two ridges. Walk between the ridges and you will come to the ridge between North and Middle Sisters. From here just follow the ridge and then the trail up to the summit. Lots of sand.
May want crampons for the glacier depending on conditions. In the morning it gets pretty glazed being on the west side of a mountain.
Total distance is just over 7 and 1/4 miles from trailhead to summit with about 5400 feet of elevation gain.
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