Chephren Couloir Dry Loose Incident



Incident occurred climbing the main Mount Chephren couloir while boot packing, approximately 150 m vertical above the fan. Size 1.5 - 2 natural triggered, ran probably 200 m. Cause was dry loose from the overnight snow, we did not see the trigger point. Most likely triggered by sluff or spindrift which accumulated in the couloir. No burials; only a twisted ankle, minor laceration requiring stitches, and a lost ski amongst the group. Conditions at the fan looked favorable, light wind and some flurries and less than 10 cm of accumulation on a very solid melt-freeze crust, and temperatures well below freezing. The fresh snow was deeper in locations within the couloir up to approximately 25 cm, that or the crust had disappeared. The snowpack below the recent/soft snow was boot-firm. Some minor evidence of older sluffs observed when we entered, but nothing unusual for this type of terrain feature. About 5 minutes before the incident several larger sluffs were observed as winds picked up. Almost immediately after a discussion on turning around, a large sluff came from above and carried all members of the party down the couloir. We consider ourselves very lucky that only bumps and scratches occurred and were able to leave the area safely. Takeaways from this incident that our group discussed afterwards - The effect of Spring may have had degraded the risk of dry loose in our minds, a more typical mid-winter concern. -Focus on variations from the conditions described in the avalanche forecast to change terrain decisions - Failure to fully understand the potential for overhead risk - poor visibility of the top of the line due to snow and fog -Increase sensitivity to even small signs of instabilities especially when in terrain traps -Awareness to change in conditions from expectations (more snow and higher winds than we had used to evaluate our terrain choices when planning)