Northwest Avalanche Center

Observation: Public

All Observations

Observation Details

Name:
Zack Wentz
Observation Date:
November 22, 2020
Submitted:
November 23, 2020
Zone or Region:
West Central
Activity:
Skiing/Snowboarding
Location:
Subalpine Peaks East of Darrington

Observed Avalanches

Did you observe any avalanches? 
Yes
Avalanche Type:
Soft Slab
Size:
Size 2: Could bury, injure, or kill a person
Elevation:
5400ft
Aspect:
S
Comments:
Location: Observed numerous old Na sz 2 storm slab avalanches on S facing slopes at TL.
Depth: 25cms on storm instability
Start zone incline: 40 degrees
Avalanche width: Approx. 60ft
Photo:

Signs of Unstable Snow

None reported

Observations

Avalanche Obs:
-Observed numerous Na size 2 storm slabs on a 40 degree S facing slope at treeline. Avalanches failed in a density change in the storm snow down 25cms. See details above.

Snowpack Obs:
-S facing slopes at TL: Performed numerous hand shears on a 40 degree slope at TL. We observed easy, sudden fractures down 10cms on a new sun crust/storm snow interface, and moderate, sudden fractures down 25cms on a storm snow density change.
-N facing slopes at TL: Ski pen in sheltered areas was significant (30cms). 30cms of F- snow sits atop 4F hardness rounds, which sits atop a P+ rain crust down 50cms.
-N facing slopes at TL in wind-loaded areas: We performed a compression test on a NE facing slope with wind-loading at 5700ft. Compression test yielded no results (CTN). Shovel shear tests resulted in a sudden planar fracture down 13cms on a storm snow density change & a sudden planar fracture down 30cms on a density change. HS: 125cms

Weather Obs:
-Sky: Overcast in AM & PM, with cloud ceiling dropping in PM.
-Precip: Nil in AM; S-1 in PM
-Winds: Nil in AM; L winds from the SW in PM

Riding conditions were amazing and better than expected! Such a great day out!

-Zack Wentz

Media

One of many Na sz 2 old storm slabs on S aspect @ TL
Image of north aspect & wind-loading

Advanced Observations

Observed Avalanche Problem #1: 
Storm Slab
Comments: 
Location: Numerous Na sz2 storm slabs on S aspect at treeline
Potential Size: Up to 2
Likelihood of triggering: Unlikely-possible
Layer depth/date: 25cms down on storm snow interface
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