The Grand Rocher has a reputation for being a safe route for skiers and snowshoers although anywhere the slopes exceed 25 degrees is potentially at risk from avalanche. It is probably safer when the snow is deep, fresh powder as the series of little slopes gives a good opportunity for sluff management.
Today was different, no overnight refreeze and an exothermic snow pack where it was possible to poke a ski pole down through all 120cm to ground level. The main climbing route has been compacted by skiers and snowshoers and seemed relatively safe, the slopes never exceed 20 degrees and tend to follow a ridge on the final section. I stopped at 1850 meters just at the top of the forest after crossing the cross country trails.
The visibility on the way down was not good, about 50 meters, I couldn’t see the lower trees in the photo above (the photo has had quite a bit of enhancement). This reminds me of an important point, even if the normal route is safe it may not be possible to stick to this trail if the visibility is poor.
There was about 10-15cm of fresh snow. It was sleeting rather than snowing at this altitude with little wind.
At around 1760 meters I skied round a tree and a circle of about 3 meters collapsed under my weight. This seemed to be the old snowpack (about 100cm). It may have been due to a hollow or rocks below as these terrain features are quite common on the route. The collapse was just by the tree in the center of this photo. The slope is about 25 degrees at this point and about 50 meters long before flattening out to 15 degrees.
I got the impression that the rest of the slope was about to go so skied across to the right of the photo where the slope flattens. The slope broke away behind me and slowly slid downhill. There was a nasty crack from one of the trees. The slide was about 15 meters wide and around 30cm deep. It had taken the 10cm layer of fresh snow and the 20cm of old snow that had fallen 2 weeks ago. I got the impression that it could break the leg of a climbing skier or snowshoer or maybe even bury them at the run out point.
grid: 06 03’, 45 19’
temperature: 2C @ 1450 m
snow level: 1650m dropping to 1400m, no wind
slope: 25 degrees, slide triggered close to tree on convex roll-over
date: 17 march 2011 / 15h00
avalanche risk given by meteo france: 2 rising to 3 in the afternoon, risk principally given as slabs forming at altitude