Professional Field Report

Basic Information

Observation Details

Observation Date:
March 22, 2020
Submitted:
March 23, 2020
Observer:
SAC - VandenBos
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
East Fork Big Wood

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Isolated
Isolated cracking and collapsing on shady slopes where snow from past 9 days sat on weak snowpack that developed during prolonged drought.

Bottom Line

Likelihood of triggering a slide on 3/14 interface is gradually decreasing as overlying slab facets. But, you'd be hard-pressed to talk me into committing to a steep, shaded slope.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Wind:
Light

Thin, high clouds for much of the morning hours, dissipating into the afternoon. Calm to light winds blowing out of a variety of directions. Snow surface heated up slowly.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
1
SE 8600' 		D1.5 O-Old Snow 40cm N-Natural Relatively fresh slab. Debris appeared to be wet in character. Observed from a distance, so hard to be certain on nature of release mechanism, but suspect that solar radiation played a role. None

Snowpack Observations

Went out to check on persistent slab problem in the southeastern portion of the forecast area. Dug on sheltered NNW aspect at 8,400', where HS=120cm. Snow since 3/14 had settled to 40cm, much of which had faceted. Below this it was facets of gradually increasing size and variable hardness (4F- to F-) to the ground. 12/7 interface was still evident and reactive to CPSTs (scores in the low 30s/110 to END), but unreactive to ECT. I even found a few SH grains here. 3/14 interface yielded consistent ECTPs in the 11-14 range and CPST scores in the low 40s/110 to END. 3/17 interface (down 15cm) looked ugly, with FCsf obvious in pitwall, but didn't produce propagating pit results, likely due to lack of a slab. The current surface is considerably faceted and capped with 1-2mm SH on sheltered mid elevation slopes. This snowpack will continue to react poorly to additional loading.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
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: 3/14, down 40cm

Terrain Use

Avoided avalanche terrain on shaded slopes