I climbed upper Yocum Ridge in mid march 1983 with Mark Bebie. Fred Beckey made the first ascent in april(see Challenge of the North Cascades). We got on the ridge crest above the 3rd gendarme because it had too much rock showing. the 3rd gendarme is on the cover of J wickwire's book "addicted to danger" you don't necessarily need real cold conditions, just well frozen, and the more snow/ice the better as the rock is really rank. Since it's at fairly high elevation and west facing it stayed well frozen for us in march the entire climb.
We were there in a clear period after a warm stormy period which plastered the climb beautifully, and the glop froze up good. This is the kind of conditions you want as pro is very hard to come by. The better pro was usually the rope running over natural features and your buddie's body weight. We did get a few good screws in in places but usually had to do a lot of chopping away the rime to get to good ice, and even then it often bottomed out. The beauty of the rime feathers is outstanding, but this climb demands boldness.
Climbing up the south side of the ridge to reach the crest had a little bit of mixed at the start but we running belayed to the crest, including thru a snow/ice tube, like I've heard about climbing rime formations in Patagonia. The ridge crest climbing was spectacular, 2 tool self belay/buddies bod and rope was only realistic pro. We went quite close to the crest at the big step,(on the south side) much higher that the route line shown in Thomas's book. This was the crux, stemming a crap rock with good but thin ice dihedral, no intermediate pro altho we had a good 2 screw belay.One of the scariest 25 feet I've dealt with in 25yrs in the mountains. I top belayed Mark with a body belay from over the north side of the crest. rope trenching here would have held a following fall. From there it was cake to the top. A very esthetic,beautiful, but scary climb.
I've gone back to Hood in winter because the rime experience is sooo cool.(more moderate stuff) "poor man's Patagonia". Hood can be done in a weekend from Seattle. tools with longish picks get thru the rime better to the harder ice below. also 60cm straight tools are prefered because you may do a lot of climbing on shafts.