Southern Gallatin

Large dry loose triggered from spin drift

Date
Activity
Skiing

While 3 of us were on ascent( about 2/3 height) we witnessed a large spin drift off the climbers right wall which entrained a lot of snow turning into a significant dry loose event. Our 3rd who was a little ways behind got carried to the apron. There was a 2nd party behind us just above the apron that followed us up the couloir. Their crew of 4 was carried as well. The 2 of us that weren’t carried went into search with our beacons and skied down the the apron where we found everyone on top and luckily uninjured.

We never had communication or visual of the other crew on ascent until moments before the incident.  
 

I would classify the avalanche as a dry loose D2. Their was evidence of several small avalanches from previous days in the couloir. Boot pen on ascent was 24-35cm

Region
Out of Advisory Area

Explosive and skier triggered wet slabs at Y.C.

Yellowstone Club
Northern Madison
Code
WS-AE-R4-D2
Elevation
8400
Aspect
NE
Latitude
45.23110
Longitude
-111.44100
Notes

"We also conducted avalanche mitigation on our Cabin’s Road at 4:30pm. The snowpack in this zone doesn’t get skied and is representative of the backcountry. The slope is ENE around 8,400’. Several wet slab avalanches were produced with explosives and ski cutting. The avalanches ranged from R4/D2 to R2/D1. They all hit the road and several crossed, and buried, the Cabin’s Road. Although most of this mitigation was done with explosives, it took minimal effort with skis to get snow moving. The crowns were 2-3’ deep and ran on the ground."

Number of slides
2
Number caught
0
Number buried
0
Avalanche Type
Wet slab avalanche
Trigger
An explosive thrown or placed on or under the snow surface by hand
R size
4
D size
2
Problem Type
Wet Snow
Images
Human triggered wet slab, YC
Slab Thickness units
centimeters
Single / Multiple / Red Flag
Multiple Avalanches
Advisory Year
21-22
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