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Professional Observation

Basic Information

Observation Details

Observation Date:
December 28, 2019
Submitted:
December 29, 2019
Observer:
SAC - VandenBos (off duty), Peterson
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Easley Peak

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Widespread
Very small natural avalanches had failed in heavily wind-loaded terrain at upper elevations in the Boulders. Widespread, small collapses on 12/7 SH in the flats of the Boulder foothills. Isolated cracking in freshly deposited wind drifts.

Snow Stability

Stability Rating: 
Fair
Confidence in Rating: 
Moderate
Stability Trend: 
Steady

Bottom Line

Wind that started in late afternoon of 12/27 had transported significant amounts of new snow, creating fresh drifts in exposed terrain that were sensitive to the weight of a skier. In the Boulders, along exposed major ridge lines, these drifts were quite stiff (P) and up to 30cm thick.

Media

This wind slab failed naturally in the Boulder Mountains on a west facing slope at 10,200'. The slab was dense (pencil hard) and failed on a slick, alpine surface. Continued winds drifted in much of the crown, nearly obscuring evidence of this slide.
Moderate to strong northerly winds transported snow for much of the day on Saturday (12/28). This photo shows plumes of wind-transported snow along the crest of the Western Smoky Mountains at sunset.

Advanced Information

Weather Summary

Cloud Cover:
Clear
Wind:
Strong , N

Steady moderate north winds blowing above 9,000', increased to steady strong above 10,000' with occasional extreme gusts. Observed significant amounts of snow being transported in the Western Smokys throughout the afternoon.

Avalanche Observations

Spotted a few small drifts that failed naturally in heavily loaded terrain. These drifts were sitting on either slick alpine surfaces or stacks of facets.

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
Persistent Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 12/7 SH
Faceting/breakdown of overlying slab is making it harder to trigger large, far-traveling collapses. However, numerous small collapses were experienced at lower elevations. In middle elevations this problem wasn't present where we traveled (likely a combination of poor environment for both SH generation and pre-burial preservation). With a significant load, I'd anticipate that this problem will rear its head again.

Terrain Use

Avoided steep terrain with recent wind slabs. Avoided avalanche terrain where 12/7 SH existed with a strong overlying slab.

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