Northwest Avalanche Center

Observation: Public

All Observations

Observation Details

Name:
BE/MB
Observation Date:
November 23, 2021
Submitted:
November 23, 2021
Zone or Region:
East Central
Activity:
Skiing/Snowboarding
Location:
Grindstone Mountain

Triggered Avalanches

Did you trigger any avalanches? 
Yes
Was it intentional? 
Yes
Avalanche Type:
Hard Slab
Size:
Size 1: Relatively harmless to people
Elevation:
6700ft
Aspect:
N
Comments:
We did several ski cuts triggering three wind slabs on both Eastern and Northern aspects. Please see attached pictures below for explanations. We encountered light to moderate snowfall through the entire day, and noted a predominant strong Westerly wind along the ridge tops, as well as micro-currents pushing the winds in various directions at lower elevations. Otherwise we saw no further signs of natural avalanche activity.

Signs of Unstable Snow

Did you see shooting cracks? 
Yes, Isolated
Did you experience collapsing or whumpfing? 
No

Observations

Please see attached photos for further clarification.

Media

This windslab was triggered via a ski cut of an isolated slope. This occurred just over the top of a ridge on a eastern lee aspect at 6900ft with a slope angle of 40 degrees. The crown measured approximately 20ft long with an average slab thickness of ~10 inches.
Same small windslab from previous picture at the top.
This windslab occurred during the ski cut of a slope on a Northern aspect at 6700 ft, with a slope angle of ~35 degrees. The crown measured ~100 ft wide with an average slab thickness of 4-5”. HS-ASc-R3-D1

On this aspect/elevation we found a total snow depth of 55cm, with a hard rain/ice crust composing the bottom 20cm of the snowpack.
Same as previous photo, from below.
Shooting cracks noted above already triggered slide.
Public Field Report: Grindstone Mountain

Advanced Observations

Observed Avalanche Problem #1: 
Wind Slab
Comments: 
WordPress Lightbox