Our primary concerns were two surface hoar layers from late January that were buried about 20-30 cm down. Other concerns were the Dec 29 surface hoar down 70-90 cm and a new surface hoar layer buried Feb 9 which was down about 10 cm by the end of the week. This Feb 9 layer was combined with some suncrusts on southwest aspects, but that crust was not widespread.
Although all these layers were reactive to some sort of test during the week at one point or another, only the late January layers reacted to skiers. Very soft slabs lay atop them. We triggered small avalanches in two different zones but they both had the same terrain characteristics: 2300-2400 m, east aspect, with slight wind effect. In one area we purposely triggered about a dozen size 1 to 1.5 very soft slabs that failed on surface hoar that lay on an old, hard bed surface from a previous avalanche cycle. In another area we accidentally triggered a couple more size 1 avalanches about the size of tiddlywinks. The bed surface was softer here and the slab didn't propagate very far.
I suspect the surface hoar in the upper part of the snowpack will become more reactive with any slight weather inputs: a bit more snow, a bit of wind (we basically had no wind all week), some warming or some sort of combination of all three. This may be happening as I type this.
We had a lot of fun this week with minimal interaction with the instability by avoiding areas where we witnessed signs of unstable snow and avoiding terrain that our nearest neighbours were triggering avalanches in. We were still able to ski moderate sized slopes up to 40 degrees all week, although with any sort of change in the weather we would have had to pull on the reins pretty quickly!
Mark Klassen
Mountain Guide
www.alpinism.com