Sheep Mountain Avalanche Fatality

On December 19, 2015 at approximately 1 p.m. snowmobilers triggered an avalanche on the SE face of Sheep Mountain outside Cooke City from low on the slope. The avalanche caught three people, partially burying one and fully burying the other two resulting in one death. The avalanche was estimated to be 100 feet wide, 400 feet vertical and 3-4 feet deep with a measured runout angle of 28°. The slope angle at the crown was assessed to be steeper than 40°. The victim’s head was buried six feet deep and CPR was administered, but he never regained vital signs. The classification of the avalanche is SS-AM-O-R2.5-D2.5 (a soft slab avalanche triggered by a snowmobiler in old snow that was small to medium-sized relative to the path, yet big enough to kill a person or damage a car). The avalanche danger was rated HIGH on all slopes and an Avalanche Warning was issued the morning of the 19^th.