Observations – Canyon Road – Peaks 3 & 4

Obvious signs of instability:

• D1.5 human triggered avalanche with energy and wide propagation on the southerly side of the ridge while traversing from Peak 3 to 4
• Recent natural avalanches, as evidenced by small D1 crowns in wind loaded areas
• Localized shooting cracks in wind loaded areas
• Blowing snow with obvious wind loading

Weather:

• Cloudy to obscured skies with an almost continuous, sleety, light snowfall through the day (glazed clothing and gear; capped the surface with a thin, weak, and easily breakable crust in areas)
• Temps in the mid to upper teens throughout the day
• Moderate to strong southerly wind throughout the day

Surface conditions:

• Below ~2500′: very little snow coverage (snow was dry and powdery in the morning, but heavier and wetter by evening)
• ~2500-3500′: pleasant, wind-deposited powder in the Peak 3 & 4 gullies
• ~3500’+: generally supportable windboard, with softer wind deposits in places

Discussion:

Skinning just below the southerly ridge triggered this D1.5 avalanche on buried surface hoar identified in observations from the past two weeks (12/12/2014 & 12/19/2014):

Shooting cracks down from the ridge boot track:

Energy and wide propagation:

Textbook trigger from a thinner, rocky area of the snopwack:

BIG, standing, and intact surface hoar is the culprit: