Skier triggered (?) avalanche on Bishop Bowl moraine

AVALANCHE OBSERVATION
Lower Bishop Bowl

Drainage:

Submission Info
Bob Harrington
Volunteer Observer
Tuesday, February 12, 2019 - 6:15pm
Red Flags: 
Recent avalanche activity
Recent loading by new snow, wind, or rain
Obvious avalanche path
Terrain Trap
Avalanche Type: 
Dry
Slab
Slope: 
33degrees
Trigger type: 
Other - explain below
Crown Height: 
1 ft
Aspect: 
Southeast
Weak Layer: 
Other - explain below
Avalanche Width: 
100ft.
Terrain: 
Near Treeline
Elevation: 
8 600ft.
Bed Surface: 
Unknown
Avalanche Length: 
250ft.
More detailed information about the avalanche: 

We went up to the Aspendell area this morning.  When we were driving past the parking for Bishop Bowl on 168 at about 0930, we noted a couple of skiers starting to ski down the lower part of the moraine, the first skier traversing into the the top of the largest and most continuous of the SE facing gullies that run down to Bishop Park Campground.  We parked a few minutes later at the end of the plowed road in the back of Aspendell that can also be used to access Bishop Bowl (Cataract Road).  We noticed that there was debris coming out the bottom of the gully that the skiers were descending, and that the skiers were working their way down next to the debris. We skied over to the debris (photo) but the skiers had departed to their vehicle at the parking on 168.  It was not clear from their tracks whether they triggered the the avalanche directly, remotely, or if they just happened to be there when it released.  It's also possible that the avalanche occurred before they entered the slope and we hadn't noticed it, but if that were the case I doubt the first skier would have chosen the initial ski cut that he did.

The avalanche was R3D2 in size.  If the skiers were caught, they soon freed themselves.  The feature that slid is a wind deposition pillow/cornice that often slides when loaded by the wind.  A crown was visible above the cornice lip (visible in the photo with the skier) that looked to be a few inches to about a foot. It may also have involved some cornice fall.  The photo with the skier in it was taken about 1000 hrs shortly after we first noticed the debris; the other photo was taken from 168 at about 1330 hrs, and by that time, the crown had blown in (the prominent white line is a wind erosion feature).

 

 

Avalanche Photos: 
Blowing Snow: 
Yes
Cloud Cover: 
50% of the sky covered by clouds
Air temperature: 
Below Freezing
Wind Speed: 
Strong
Air temperature trend: 
Warming
Wind Direction: 
Southwest
More detailed information about the weather: 

Stong gusty southwest winds, swirling every direction at ground level.

Lower Bishop Bowl 37° 14' 34.7064" N, 118° 36' 2.8116" W

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