Avalanche Independence Peak - Onion Valley

AVALANCHE OBSERVATION
Independence Peak

Drainage:

Submission Info
Josh Feinberg
Wednesday, April 29, 2020 - 11:00am
Red Flags: 
Rapid warming
Avalanche Type: 
Wet
Slab
Trigger type: 
Natural
Crown Height: 
3 ft
Aspect: 
Northeast
Avalanche Width: 
40ft.
Terrain: 
Near Treeline
Elevation: 
10 500ft.
Bed Surface: 
Old Snow
Avalanche Length: 
2 000ft.
Number of similar avalanches: 
1
Number of partial burials: 
0
Number of full burials: 
0
More detailed information about the avalanche: 

This report includes details from Inyo County Search and Rescue and the male skier involved in the accident that was able to self arrest and not get swept down the chute:

A party of two skiers, one male, one female, both in their mid to late twenties, set out around 9:30am on April 29th to ascend, then ski a prominent canyon on the northeast side of Independence Peak, above the Onion Valley Rd near the Kearsarge Pass trailhead. After skinning up the chute for ~1.5 hours and gaining a couple thousand feet, at ~11:00am they stopped on the edge to transition from skinning to booting.  While they both had their packs off they heard then saw an "explosive fast moving" avalanche release approximately 300-500' above them. With no time to react, both were caught up in the moving snow but the male was able to grab on to some rocks until the moving snow passed. The female, though, was carried out of sight down the canyon.  

The male subject, now missing his skis and backpack, was able to move down the canyon and eventually found his partner (and half of a ski) on the skier’s left edge of the debris, unburied but with rib and lower back injuries severe enough that she was unable to continue out, having been carried approximately 1,000’ by the avalanche.  

Details of the initial contact are not clear, but shortly after  11:00am the Inyo County Sheriff received a call concerning some sort of slide on the Kearsarge Pass Road, and the Inyo County Search and Rescue team was deployed along with resources from the CHP including CHP helicopter H40, Inyo County Sheriff and CAL Fire. The total response included over 40 personnel. The Inyo County Sherrif and a Deputy were first on scene and were able to boot up to the skiers.  Upon arrival of the SAR team, the SAR team snow safety officer and other team members evaluated avalanche conditions and concluded that the area continued to have high avalanche danger conditions. In addition to a successful rescue of the subjects, a goal was to minimize the number of respondents exposed to the avalanche hazard, so the SAR team and CHP determined that a helicopter hoist offered the fastest and safest means of extricating the injured subject. H40 was able to insert one SAR team member at the subject’s location and the patient was subsequently evacuated by the helicopter and taken to Southern Inyo County Hospital.

The avalanche started in steep NE facing terrain around 10,800', presumably as a loose snow slide.  At around 10,400' a large wet slab avalanche released on a deeper weak layer with an estimated 2’-4’ crown. The total slide length was about 2,500’, and measured a D2.5/R3.  Rapidly warming temperatures, parly cloudy skies, and a weak overnight refreeze of the snowpack were all likely contributing factors.  Weather from nearest remote weather sensor - Charlotte Lake (10,400'):  -4/29:  Low Temp of 35F at 4am.  Temp rose from 41F to 51F between 8:00am - 8:45am.  56F at 11:00am, up to a high of 58F at 12:00pm.  -Althought the previous day high temperatures rose to 60F on 4/28, the skies were clear, and low temperatures the night before dropped to 33F.  The party said that winds at the time of avalanche were light. 

Additional details and comments:  The party estimates that ski penetration while they were skinning (mostly in the shady side of the chute) was between less than an inch to barely 2", but that on the sunny side it appeared to be softening more.  They underestimated the superficial surface refreeze that they felt was deeper. They both had transeivers on, but their rescue equipment in their packs was swept away by the slide, as they were in the middle of transitioning.  Had the slide occured minutes earlier when they were still skinning, or minutes later when they were booting with packs and skis on their backs, both of their outcomes could have been much worse.  The skiers had ~5yrs and ~12 years of backcountry experience, no formal avalanche education, but quite a bit of informal education from experienced partners.  The skiers both express deep gratitude to Inyo SAR the Sheriff's dept, and all involved in the rescue operation.  

 

 

Avalanche Photos: 
Blowing Snow: 
No
Precipitation: 
None
Accumulation rate: 
None
More detailed information about the weather: 

 

 

 

Number of People Caught: 
2
36° 45' 44.4996" N, 118° 19' 37.308" W

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