Observation: Public

Name:

Matt Lubar

Observation Date:

January 28, 2021

Submitted:

January 28, 2021

Zone or Region:

West North

Activity:

Skiing/Snowboarding

Location:

North Twin Sister

Did you trigger any avalanches?

Yes

Was it intentional?

No

Avalanche Type:

Soft Slab

Size:

Size 1: Relatively harmless to people

Elevation:

4300'

Aspect:

NW

Comments:

I triggered a small soft slab avalanche on a steep convex roll greater than 35 degrees that broke about about 1ft deep and ran on a crust layer.

Photo:

Did you see shooting cracks?

Yes, Isolated

Did you experience collapsing or whumpfing?

Yes, Widespread

We traveled in the basins to the North of the North Twin Sister again today, and continued to observe cracking in areas where the wind had transported snow and formed deeper drifts. We observed consistent whumpfing as we pushed into new terrain that we believed to be occuring within a layer of faceted grains sandwiched between a thick, stout crust below and a thin crust above. We did not see any avalanches occurring in association with the whumpfing. In some areas, only 1-2in of low density snow sat atop a stout crust, while we found drifts of up to 2ft in other areas. It began snowing around 9am (S2) and continued at this rate until about 11am when it began to slow (S-1 to NO). Winds were calm for most of the day, even above treeline, with light gusts picking up at ridgetop around 1:30pm.