Avalanche on Flagpole

Location Name: 
Flagpole Peak
Region: 
Echo Summit Area
Date and time of avalanche (best estimate if unknown): 
Sun, 04/15/2012 - 10:00
Location Map: 
United States
38° 50' 44.1276" N, 120° 3' 12.8628" W
See map: Google Maps
US


Red Flags: 
Rapid warming
Obvious avalanche path
Terrain Trap
Observation made by: Professional Observer
Avalanche Observations
Avalanche Type: 
wet,loose,
Slope: 
40degrees
Trigger type: 
Skier
Aspect: 
Northeast
Weak Layer: 
Storm Snow
Avalanche Width: 
150ft.
Terrain: 
Below Treeline
Elevation: 
8 000ft.
Bed Surface: 
Old Snow
Avalanche Length: 
1 000ft.
Number of similar avalanches: 
3
More detailed information about the avalanche: 

WL (WS) AF(u) D2 R3 S(I) M

Pic 1: ascent route, with ECT results upon ascent. Note point release top center of image along high traverse that initiated larger slide.

Pic 2: same pic that better shows ascent route.

Pic 3: taken from below, shows ascent route with "x" ECT location. Debris that we ascended under rocks climber's left  was from yesterday. Bed surface = old crust

Pic 4&5: debris on trees ~1.5m deep

Pic 5: looking across at widest part of path.

Pic 6: looking upslope from toe of debris (~1m deep)

Mitt pits showed storm snow in Moist phase, but old crust in Wet to Very Wet phase on E/NE aspects by 10am.

Similar natural activity observed on 3 nearby paths. Ralston, Talking, Becker, Echo also had loose wet activity, but some may have been from yesterday (24hr and + slab crowns visible as well). Yesterday's wet loose on Flagpole stayed within storm snow, and did not slide on old crust. Today's did slide on old crust and entrained significantly more snow.

50m adjacent to 4/12 obs that showed propogation potential on Flagpole saddle: 2x hard ECTN just above old crust.

Avalanche Photos: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
Clear
Air temperature: 
Above Freezing
Wind Speed: 
Calm
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Accumulation rate: 
None
More detailed information about the weather: