The Stuart Glacier Couloir was first climbed in June of 1944 by Helmy Beckey and Larry Strathdee. Most years now, that would not be a fun time to climb it. The route is best in cold, snowy conditions, and the months of March, April and May at the latest provide the best conditions.
The character of this route is similar to the Ice Cliff Glacier. Both routes require good snow conditions to be safe, and both feature snow to 50 degrees. Although the Ice Cliff Glacier has a strikingly long section of continuous steep snow climbing, the Stuart Glacier Couloir is my favorite of the two for the snowed up rock climbing on the summit block.
That said, the route should not be attempted in warm conditions or rain or heavy snowfall. I have two different friends who have walked up to the base, geared up to climb and then been sent packing by avalanches sweeping the couloir. Another friend who did climb it in hot weather had a tale of sugary, holdless snow and a crashing boulder. For my part, I was lucky to have perfect conditions, exactly as summed up well by Nelson and Potterfield in Selected Climbs in the Cascades:
"Slightly unstable spring weather frequently makes the best scenario for climbing the Stuart Glacier Couloir, with cool temperatures and inconsequential snow flurries."
This route is really a winter/spring climb, so the only feasible way to approach it then for a two day trip is from the Mountaineer's Creek trailhead. Good directions for that approach are on the Ice Cliff Glacier route page here.
From the basin below the Ice Cliff Glacier, hike up the moraine almost due west to reach the base of the North Ridge. Continue hiking up onto the Stuart Glacier on the right side of the North Ridge. It is advisable to rope up by this point as crevasses were visible for us even in spring. The couloir will become more obvious above you. The entrance is at 7,800 feet, and guarded by a bergschrund that should hopefully just require a step across. If you want to take a well-deserved break here (it's been 2,400 feet of snow climbing since camp), consider stopping on one side of the couloir or the other, not directly below.
It is also possible to approach the couloir from the south side of the mountain via Goat Pass and traversing across the upper part of Stuart Glacier to the base of the climb. This would be the same approach as for the upper North Ridge Route.
From its base, the couloir is climbed directly with most parties using the right exit on to the West Ridge at the top. Conditions vary considerably from year to year and the amount of belaying needed depends on conditions and the strength of the party. The angle quickly climbs above 40 degrees and stays there. At a constriction there may be 20-30 meters of exposed ice. If roped up a solid belay is advisable.
Above the constriction the angle eases somewhat, but is still over 40 degrees and feels like it has more avalanche potential (the slope is much wider here and uniformly steep, and I think it gets more sun). For our part, we experienced massive crampon ball-up above the constriction and had to remove them carefully from a stomped-out platform.
Photos of Climbing in the Couloir:
It's a fair bit of work to reach the West Ridge Notch, but the views become extremely rewarding in here. Once at the Notch, a completely different climb begins. Having chosen optimal conditions for the Couloir, you can now expect snow on 4th and low 5th class rock. Follow the route as described for the West Ridge. Variations are possible. The main idea is to go up the ridge from the notch for a couple of pitches, then swing out onto the North Face at a higher notch, and finally come around to the south side of the mountain for the final 2-3 pitches to the summit. If you come to the south side too soon, you'll be stymied by steep walls and tattered rappel slings.
I'm not much of a winter or "mixed" climber, but I found these snowed-up rock pitches very enjoyable and reasonably comfortable. We carried a rack with just a little of everything (described below). We did use the pitons 2-3 times, as snow can make it hard to find nice cracks to slot a nut in.
Hit it in the right conditions, and you'll love it.
Photos of Climbing Above the Couloir:
At the time of year that most parties will be climbing this route, snow and ice should be expected on the rock above the couloir.
DescentFrom the summit, descend Sherpa Glacier or one of the south side routes back to your camp. If you can sleep there for the night before heading out, your body will thank you. Just note that in the spring conditions, frequent punching through snow holes into creeks and tree wells will add to the fun of the hike out.
Essential GearBring some snow pickets, a couple of ice screws for the constriction, and two tools to climb the couloir. Bring crampons. Depending on the month, you might want snowshoes or skis for the approach.
Bring a rope and rack with 6 nuts, 2-4 cams, 3-4 pitons (knifeblades and baby angles). A couple of tricams are useful.
Definitely wear a helmet, and make sure you could find your way down from the summit in whiteout conditions, to the entrance of the Sherpa Glacier. Knowing the compass bearing for that from the top of the snowfield at the false summit might be important.