Large HUMAN TRIGGERED avalanche - Piute Crags

AVALANCHE OBSERVATION
Piute Crags

Drainage:

Submission Info
josh feinberg
Forecaster
Saturday, April 11, 2020 - 12:45pm
Red Flags: 
Recent avalanche activity
Rapid warming
Avalanche Type: 
Dry
Slab
Slope: 
40degrees
Trigger type: 
Snowboarder
Crown Height: 
2 ft
Aspect: 
Southeast
Weak Layer: 
Unknown
Avalanche Width: 
50ft.
Terrain: 
Above Treeline
Elevation: 
11 800ft.
Bed Surface: 
Old Snow
Avalanche Length: 
1 000ft.
Number of partial burials: 
1
Number of full burials: 
0
More detailed information about the avalanche: 

Event - 2020-04-11 - Information provided by snowboarder invovled in avalanche

One snowboarder booted up a NE facing couloir in the piute crags, then up a SE facing panel onto an East facing slope to the ridgetop.  He descended at 12:50pm, making one large sweeping turn across the E slope, made 3-4 turns down the SE facing panel, dropping below a convexity and lightly scrapped a rock and triggered an avalanche initially releasing about 50' above him at the convexity, which then triggered a much larger avalanche far above.  He was able to straight line for a bit until the snow he was on rippled and slowed him down, and he looked back at a wall of snow and was engulphed.  His airway was quickly choked full of snow and he was carried 900-1000' vertical into the moraine where the slide lost momentum as it rose a slight incline and stopped.  He was buried in what felt like concrete up to his neck with his head and one hand above the surface, ontop of what he estimated was 15-20' of avalanche debris.  He was able to clear his own airway, and his partner who stayed down below to film was able to get to him in 30 seconds and begin digging him out.  His board was snapped in two, but fortunately he only suffered minor injuries including strained ribs, a sore throat and some fluid in his lungs from the snow shoved down his throat.  The party was able to self-evacuate.  The attached movie was taken by their friend who remained at their camp near Birch Creek.  That friend after witnessing the slide could not tell what happened to his friends and called search and rescue, and then later called them off.        

Avalanche Details

-R3-D2.5 (medium size relative to path with a destructive force between burying a person and destroying a wood frams house) 

-Avalanche was a soft slab.  Estimated to be intitially a 10" crown about 50' above the snowboarder, which triggered a much larger crown far above visible from far away (2-3'?).  The avalanche was triggered at a shallow point in the snowpack, and the significant daytime warming and solar input no doubt led to the sensitivity of the slab.  The avalanche also triggered another avalanche that released below the rock bands above the apron on an East facing slope with a ~2ft crown. 

Weather

-From 6am April 5 thru 6pm April 6, 15" of new snow was recorded at the Saw Mill snow sensor near South Lake at 11,900'.  An additional 22" of new snow was recorded between early morning on April 8 thru 5pm April 9.  

-April 10 was an unsetted stormy day with snow flurries and high temperatures reaching 35°F at the Saw Mill sensor at 11,900'.  

-April 11th was a clear blue bird day with calm winds (light gusts at the ridgetop) and temperatures reached a high of 44°F at the Saw Mill sensor at 11,900', just at the time the avalanche was triggered.  

Other Details and Comments

-Snowboarder was a 28yr old male with AIARE level 1 training, carring a beacon shovel probe, with extensive backcountry experience beginning in 2013.  They noted small sloughing occuring that morning on E and SE facing terrain on other nearby mountains, and regrets not heeding that warning sign.  He feels lucky to be alive, and regrets highly that he rode such a consequential line and that his actions potentially put search and rescue at risk during this pandemic.   

-Forecaster comments:  This is a good reminder of the dangers that exist during initial warming of recent snowfall.  We feel very fortunate that this did not end with more significant injuries, or fatality.  The rider is well aware of the mistakes that he made, and is working on his own debrief that he plans to share in hopes of helping others not make the same mistakes he made.       

Avalanche observation video: 
Number of People Caught: 
1
37° 14' 21.6708" N, 118° 38' 40.1676" W
-- placeholder --

ESAC receives significant financial support from ...