Thursday, April 10, 2008


For 16 backcountry ski seasons I had a PERFECT score, until today. And it had to be the day I was skiing alone! Today I triggered a slide on a steep slope, and went for a ride, but I was able to ski out of it before getting strained through some trees. I was glad that "training kicked in".

Below a topo map for the runs I skied today at Pilot Peak:

Lines in blue are the uptracks, and in red the skied runs. The skier triggered avy (SS-AS-D1.5-R2-N, 30 cm) occurred at one of the 3 runs clustered together, the leftmost one - which is one of the steepest lines (40 + Degrees) in that area. I am glad that I chose NOT to ski the avalanche path below the cornices, and to the left of where the Avy ran. The line below the cornices was getting loaded due to today's strong winds.
The skiing was FANTASTIC - lots of powder can be found at NW, N, and NE aspects, particularly at the 7000 feet level. The East aspects were a little tricky with pockets of breakable crust. South-East and South aspects were skiing wonderful with 5-10 cm of cream on a very carvable and supportive crust layer. And it is still pretty much winter at Mores Creek Summit, with no signs yet of spring.

The following picture shows the area I skied the 3 runs. The picture was snapped after the first run.

The snowpit data is summarized next:

Early in the day, I skied two moderate lines (less than 34 degrees steep, and uniform without convexities). Before the third run, I spent time on a Snowpit Plus to gather stability data. The snowpack where the SnowPit + and tests were conducted provided data for a Strong snowpack (CTH), little fracture initiation energy available (Q2&Q3), no fracture propagation capability, and moderate structural lemons (Weak Layer metamorphosis was observed - advance rounding of facets - suggesting sintering of the weak layers).

Based on the snowpit data, I proceeded to a much steeper ski line. After ski cutting a couple of significant wind-loaded pillows at the top of the ski line without any reactivity, I dropped in.

While skiing down something caught my attention (not sure - but I think it was the rumbling noise behind me). I looked over my shoulder, and I saw a wall of snow about half a meter high coming to me at a very high rate of speed. As I started to ski to the right in order to move out of the avy's way, the avy NOW all around me started to accelerate me and get my legs from below me. My first thought was "Puneta (cursing in Spanish) - I am by myself" - and instantaneously collected myself to concentrate on the task at hand. FIRST keep the skis below the body at ALL COST and turn to the side of the slide - while at the same time I VERY VERY VERY forcefully pushed the poles into the bed surface to arrest my speed, and allow the turbulent wave and leading edge of the avy to pass me. After the turbulent wave passed - I regained good control of the skis - and skied away from the avy through less turbulent snow flow.

The next two pictures show the slide about halfway up of its track, looking uphill. On the second picture I used the camera zoom.

My concern about this avy was the speed and the strainer trees through which this avy ran. The avy ran not more than 300 feet and the debris field was not very deep, perhaps 30-50 cm. The next two pictures show the debris between the trees.

The MISTAKE I made was to forget last Sunday (April 7th) observations, which I will include again for reference:
Interestingly enough, these areas were always in protected aspects, suggesting a recent surface hoar event. Q2 scores and other observations suggest that the snowpack is gaining strength, not surprising considering the warm temperatures. It is likely that similar stability assessment could apply to Mores Creek Summit and other Central Idaho Mountains since surface hoar or near surface faceting tends to affect a large region.

With the above snowpack assessment, it is important that we do NOT let the guard down. Avys are still possible in steep terrain. Such terrain is very limited in the Bogus Basin sidecountry. But it can be found in some areas of More Creek Summit along with unforgiving terrain traps.

After the slide I climbed back up again - and found facets above a crust below 30 cm of snow. That layer was not present at the snowpit location. Also, I underestimated the effect of today's wind at the ridge top - where the snow became brittle and slabby and able to initiate and propagate fractures.

For the small size of this slide I was surprised how much punch it carried! I had never ridden a slide- until now - but had seen many. It will be prudent to stay vigilant during the next few days, since the forecasted warmer temperatures can further raise the avy risk temporarily (next 48 hours).

And remember - There is no better piece of data for INSTABILITY than an actual AVALANCHE!