In reply to Doug:
Just coming back to this avalanche, large spontaneous avalanches are not expected at risk 2. That then poses the question of why it was so big.
Could it have been triggered by someone high up on Mt Mort?
Was it just a tragically one off slope that was heavily loaded (the guide interviewed suggests this) - maybe one that has resisted natural purges that other slopes have been subject to during the last few days/weeks?
Does it show that the Swiss interpretation of the risk scale is seriously underestimated? I've always noticed this - for instance when it's 4 in CH it's usually 5 in France.
It's possible to trigger a slope from below but in this case it does seem unlikely given that the upper and lower slopes are more or less separated from each other by a band of crags - see photo richlan posted (which by some strange coincidence seems to have been taken by one of Hilary's clients on a snowshoes trip with her a couple of years ago!)
Post edited at 16:12