Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
December 11, 2021
Submitted:
December 11, 2021
Observer:
NWAC Forecaster - Josh Hirshberg
Zone or Region:
Stevens Pass
Location:
Stevens Pass Resort (4050-5600ft, N-E-S)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced

Media/Attachments

At the crown of a skier triggered avalanche. SS-AS-R1-D1-I. 5180ft, SE, Big Chief Mtn
A profile within the boundaries of Stevens Pass resort. The interface at 92cm (↓39cm) was the most problematic layer this day. 5,580ft, SE
Identifying an interface of concern ~40cm below the surface. This mid-storm layer produced test results, shooting cracks, and a skier triggered avalanche. 5,580ft, SE, Stevens Pass
A crack in a wind drift. Cracks broke to interfaces ~20cm and ~40cm below the surface within storm snow layers. E, 5180ft, SPMR
Investigating the crown of a skier triggered avalanche. It ran 250ft vertical on the interface of the new /old snow ↓40cm broke about 75 feet wide. SS-AS-R1-D1-I. 5180ft, SE, Big Chief Mtn

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
30°F
Wind:
Light , W
New/Recent Snowfall:
HN24 60cm

Snowing S1-2 w periods of graupel. Winds were generally light and west w gust strong enough to transport snow and occasionally out of the E and S.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Dec 11, 2021 11:15 am
() 		Stevens Pass, SPMR- Aquarius run
SE 5180ft 		D1
R1 		SS-Soft Slab S-New Snow 1.5ft AS-Skier
Investigating the crown of a skier triggered avalanche. It ran 250ft vertical on the interface of the new /old snow ↓40cm broke about 75 feet wide. SS-AS-R1-D1-I. 5180ft, SE, Big Chief Mtn
At the crown of a skier triggered avalanche. SS-AS-R1-D1-I. 5180ft, SE, Big Chief Mtn
Report
Stevens Pass, SPMR- Aquarius run

Snowpack Observations

HS 120cm
Experienced cracking in wind-affected snow. Few signs of instability in wind-sheltered terrain below TL.
Profile at 5580ft, SE (see image)
Mid-storm interfaces ↓20cm and ↓40cm produced cracks, test results (CTM PC ↓40cm), and avalanches. Hard, planar results on Dec 4th crust (CTH RP) ↓101cm.

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
 Comments: Uncertainty above treeline. Some slopes, especially NTL or low elev ridges, received very subtle wind loading making them difficult to assess for wind slabs
Storm Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 40cm
Comments: Generally stubborn except for in very steep or unsupported terrain
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