Northwest Avalanche Center

Observation: Public

All Observations

Observation Details

Name:
Matt Primomo
Observation Date:
December 19, 2021
Submitted:
December 19, 2021
Zone or Region:
Stevens Pass
Activity:
Skiing/Snowboarding
Location:
Lanham Lake zone

Observed Avalanches

Did you observe any avalanches? 
Yes
Avalanche Type:
Soft Slab
Size:
Size 2: Could bury, injure, or kill a person
Elevation:
3,800-5,700
Aspect:
Comments:
We found evidence of a widespread storm slab cycle during the storm on 12/18. Most avalanches appeared to be D1.5-2's but a few were D2.5. Crowns were 40-50cm deep and often very wide. I got an up close look at one crown on an E aspect at 5,600ft above Henry Creek. It appeared to have failed on the old snow/new snow interface but it was difficult to discern.

Signs of Unstable Snow

None reported

Observations

Storm snow was still inverted in most areas we traveled, but appeared to be settling out nicely. Couldn't get much cracking or snow to move on test slopes. Some recent wind drifting had formed 4F slabs over very low density snow, and we mostly avoided these areas.
A very thin sleet crust was found at the surface above 5,200ft, with small surface hoar growing on it in a couple places right at a ridgetop around 5,500ft.

Photos:
1. D2 from the E Bowl of Mt Mastiff
2. D2.5 from the SE Face of Rock Mtn
3. D2.5 from a NW aspect in the Chiwaukums
4. Looking down the flank of a D2 into Henry Creek. SE at 5,600ft
5. Crown of the slide from photo 4, SE at 5,600ft

Media

E bowl on Mt Mastiff
SE Face of Rock Mtn
Crown off a high, NW aspect in the Chiwaukums.
Looking down the flank of a D2 that ran into Henry Creek. SE at 5,600ft
Crown depth, SE at 5,600ft
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