Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 3, 2020
Submitted:
January 3, 2020
Observer:
SAC - Martin Stefan
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
Warm Springs Drainage

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Widespread
Collapsing on persistent weak layers under wind stiffened storm slab from 12/31

Snow Stability

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

Bottom Line

On low elevation solars where the snow is thin the slab from this last storm rests on a weak, rotten base. On shadier aspects we have the usual weak layers from beginning of December still showing sings of instability.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
30s
Wind:
Calm

A calm and balmy afternoon in the Wood river valley, some thin clouds veiled the sun around 3pm.

Snowpack Observations

On low elevation solars the 12/31 storm slab rests on a weak mess of faceted crusts and just facets, at least in areas with little to no sage brush. The storm slab was getting baked and moist in the afternoon sun, but the facets below were dry.

On higher and shadier slopes 12/7 is present, at 7600' on a wind loaded open SW slope I had HS 80cm with 30cm 4f wind slab on FCxr and 12/7 60cm down. No DH, moist small FC to gnd. The sun had not baked the storm slab noticeably here.
12/7 produced ECTP24sp and a snappy PST25/100end, no result on the old/new snow interface. After leaving the pit, not more than 3m away I collapsed the whole slope.

Pit at 7600' SW slope in Warm Springs drainage. 12/7 produced ECTP24sp and PST25/100(end)

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: 12/7 50-60cm
Comments: 12/7 is present and still active in this area on everything but the sunniest slopes.

On sunny aspects clear of sagebrush the base for the 12/31 storm is another PWL, but given how thin the total snowpack is in these areas it will be isolated to planar slopes that have little to no sagebrush.

Terrain Use

I avoided avalanche terrain