Natural Cornice-Triggered Avalanche, Middle Peak, Castle Lake

Location Name: 
Middle Peak, Castle Lake
Date and time of avalanche (best estimate if unknown): 
Thu, 04/13/2017 - 3:30pm
Location Map: 
United States
41° 13' 12.414" N, 122° 23' 2.724" W
US


Red Flags: 
Recent avalanche activity

Observation made by: Professional Observer
Avalanche Observations
Avalanche Type: 
Slab
Slope: 
35degrees
Trigger type: 
Natural
Aspect: 
North
Avalanche Width: 
50ft.
Terrain: 
Near Treeline
Elevation: 
6 400ft.
Avalanche Length: 
400ft.
Number of similar avalanches: 
2
More detailed information about the avalanche: 

Near treeline avalanche triggered by a cornice break at the top of Middle Peak, Castle Lake. Large cornice fall triggered what may have been an old wind slab formed over the last several days. Due to the amount of warming and solar radiation received by the snow pack yesterday, and the fact that the top layer of snow was moist to wet, it is possible that this was more of a wet-loose avalanche triggered by the large cornice fall. Either way, plenty of snow was entrained along the avalanche's path creating enough debris to injure, bury, or kill a person.

The Castle Lake area received plenty of sun yesterday and temperatures reached a high of 51 degrees F at 15:00, 30 minutes before the observed avalanche occurred. Small roller balls, point releases, and very small and shallow wind slab avalanches were observed on steep terrain on sun exposed aspects. Two other similar avalanches had already occurred.

Avalanche Photos: 
Avalanche observation video: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Light
Air temperature trend: 
Cooling