fbpx North Sister | Central Oregon Avalanche Center (COAC)
Recent avalanche activity
Rapid temperature rise
Observation Date/Time:
Tue, Mar 2, 2021 - 2:00 PM
Three Sisters Area
Report Type:
Snow Conditions  
Travel Mode:
Ski or Snowboard  

Written Report:
Well, it’s been an interesting past week for snow conditions! First we had the big winter storm at the end of last week with lots of snow and wind (and associated avy activity), then it warmed up dramatically, then became pseudo-spring-like (hence the red flags I listed). And now it looks like more weather is coming in. Interesting snowpack times.

We were out in the storm last week doing the nordic traverse from Dutchman to Three Creeks, so got an up close view of the storm and the aftermath. Some great snow on Sat, though did see at least one skier-triggered small slab on the Proboscis at Tam Rim. On the way out we had some great views of the Sisters and they were looking good. North Sister had good coverage, though in zoomed-in pics I did notice some crowns high up on the Thayer side that probably released during the storm. On Sunday things got reaaallly hot, and on a tour that day in a nearby zone the lower elevation stuff was sticky mank, but up high and more N-facing things seemed to be holding OK.

So on Tues I decided to go out to N Sister and check things out. I wouldn’t recommend it unless an 18mi tour is your idea of a good time (granted, I know that probably applies to most people in this town, but I dunno what I was thinking…). Could drive to about 3.5 miles from the TH, the last mile of which was pretty sketchy. The snow had gone through some melt-freeze cycles and it was pretty much frozen at 0-dark-thirty and stayed like that all the way out to the moraine below the Thayer, so at least it was quick travel. There was evidence of some previous slide activity out there, with remnants of a runnel in the choke in the Thayer line but decent enough snow in the middle in a strip about board width. The snow conditions were typical for that line - all over the map. Basically every type of snow, except the hero kind - I call it “ski mountaineering” snow conditions. :) Everything seemed rideable though so I continued Vert-ing up. There was a smaller crown directly below the Camel’s hump (I’d estimate a couple feet high), and a larger one at the top of the Thayer about 20 feet below the notch. That one was a good 4+ feet or so, and had gone through some interesting transformation since it happened. Before the heat came, some snow had gotten blown over and filled it in a bit in places, then the heat came and started melting it some. The end result was that at this point it actually looked more like a bergschrund or glide crack than a crown. It was tough to get over too. Ultimately got to like 30 ft from the summit but bailed because of shallowly buried rocks on the final summit ramp, giving me visions of tomahawking 2k feet down the line. The descent started with 2 awesome turns on the remaining cold snow on the more N-ish facing ramp, and deteriorated from there. Once onto the sun-facing aspect below the notch, I sent down a small slice of wet slide (somewhat expected), which was apparently enough to sluff out any remaining decent snow in the choke lower down, which was also in the shade by now, so by the time I got there it was a horrendous frozen mess. Toeside ice axe self-belay a couple feet at a time for a few hundred vert was super fun, not to mention the 8 mi exit after all that. That line is just so tricky to time right. But hey, at least the views were great! And of course just seeing the mountains and their winter transformation cycles up close is always worth it.

Looks like everything is about to change again so this is probably obsolete info, but there you go. If nothing else we’ve got a great spring base! Attached are some pics of the crown at the top of Thayer, and a couple scenery shots just because the views were so amazing up there.