Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 12, 2020
Submitted:
January 13, 2020
Observer:
SAC - VandenBos
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Salmon Headwaters to Smoky Crest

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced
Plenty of cracking in freshly formed slabs. Wind slabs on steep, small test slope were trigger-able with moderate force.

Snow Stability

Stability Rating: 
Poor
Confidence in Rating: 
Moderate
Stability Trend: 
Worsening

Bottom Line

Decreasing stability and increasing hazard.

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Wind:
Moderate , SW

Continued light orographic snowfall throughout the day under obscured skies. Snowing S-1 to S1 from noon through sunset. Winds shifted to SW and picked up appreciably around 3pm, blowing low end of moderate at middle and upper elevations, transporting large amounts of snow. Difficult to get a handle on amount of new snow - estimating 30-40cm since start of storm on 1/10.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
2 Near Smoky Crest
SE 10,200'
D1 SS I-New/Old Interface 30-60cm AS-Skier
c-Intentional
Intentionally triggered small slabs on steep, heavily wind loaded test slope None

Snowpack Observations

Went out looking for three things:
1. Character of snow at low elevations, just off valley bottom. In the area I traveled the snowpack was very weak at lower elevations, but unresponsive in stability tests, likely due to lack of an overlying slab. Although HS didn't change drastically, the strength of the snowpack (judged by resistance to pole probing and significant change in ski penetration) increased about 400-500' above valley bottoms.
2. Behavior of 12/31, particularly where accompanied by a crust on solars. Dug at 8,500' on SSE where HS=75-85cm. 12/31 yielded variably propagating results in ECTs with moderate force and repeatably short critical cut lengths (END) in PSTs (low 20s). This layer seems to have a tricky distribution thanks to variable sky cover during formation. In some places there was not adequate solar input to generate a crust and it is much less touchy. In others it produces unstable test scores.
3. Amount of wind loading. Winds picked up significantly in the mid-afternoon, accompanied by a shift from NW to SW. Easily transporting new snow into fresh drifts in exposed 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
Comments: Slabs increasing in size and distribution into nightfall.
Persistent Slab
Isolated
Specific
Widespread
Unknown
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
Layer Depth/Date: 12/31, down 50cm where I dug (suspect deeper elsewhere)
Comments: Worst where accompanied by a crust, on mid elevation solars.
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, 11/26
Comments: The monster in the basement. Will be interesting to have a look around after these storms draw to a close and see what sort of activity occurred on these layers.

Terrain Use

Avoidance