Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 9, 2021
Submitted:
December 9, 2021
Observer:
NWAC Forecaster - Josh Hirshberg
Zone or Region:
Stevens Pass
Location:
Big Chief Mtn (4050-5600ft, N-E-S)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced

Media/Attachments

Tilt test in the top 40cm of snow. Failures occured down 5cm on the 12/9 interface and down 21cm on the 12/8 crust. 5500ft, SE, Stevens Pass Mtn Resort
wind drifted snow. E, 5,600ft, Big Chief Mtn, Stevens Pass.
Cracks in a pocket of wind drifted snow. E, 5,600ft, Big Chief Mtn, Stevens Pass.
Profile from 5500ft, SE, Stevens Pass Mtn Resort. 12/9/21

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Wind:
Moderate , W
New/Recent Snowfall:
HST 20-25cm since morning of 12/8

Cold w light snow and wind in AM yielded to strong gusts by 14:00. Snowfall intensified around 16:00.

None observed

Snowpack Observations

The average height of snow ranged from 50-70cm. We found drifts up to 175cm at 5,600ft. 12/8 rain crust ↓20-25cm was intermittent in the terrain. More prominent crust from late-Nov rain events was consistently 35-40cm below the surface. The bond above the crust was variable with some test pits producing no results. A profile at 5,500ft, SE, (see photo) yielded planar tests (CTM RP) on 0.5mm rounding facets down 35cm, just above the late-Nov crust.
While these interfaces were interesting food for thought, we experienced few signs of instability while traveling through the terrain.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 12/8
Comments: Wind slabs formed 12/8 were generally hard to trigger with cracks propagating minimally. Slabs were isolated, discontinuous, and in the immediate lee of features. Other observers reported finding evidence of wind transport further downslope in Highlands Bowl. Fresh slabs began to form at 14:00 w moderate to strong W winds.
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