Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 28, 2021
Submitted:
January 28, 2021
Observer:
SAC - Ethan Davis
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
Greenhorn, E. Fork Bigwood (All aspects, Low elevations)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Widespread
Collapsing? 
Widespread
I didn't pass through low elevation terrain without collapsing and cracking. A few collapses traveled at least a couple hundred feet, shattering small steep slopes.

Snow Stability

Stability Rating: 
Very Poor
Confidence in Rating: 
High
Stability Trend: 
Steady

Bottom Line

I observed natural avalanches on several of the low elevation N-facing slopes that I could get eyes on in the E. Fork of the Bigwood Drainage. Collapsing and cracking just beneath the new snow was widespread on a short walk at the mouth of Greenhorn. Storm slabs in non-wind affected terrain were 70 cm (28 in) thick.

Media/Attachments

Numerous slab avalanches spanned most low elevation, N-facing terrain above the E. Fork of the Big Wood River.
Storm snow accumulations have settled to 70 cm (28 in) in this low elevation location. This slope cracked and shifted downhill after a collapse I triggered from at least 150' away.

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Temperature:
31 F
Wind:
Light , SE
New/Recent Snowfall:
HST = 70 cm

Snowfall rates at or just below an inch an hour. Easterly outflow drainage winds were drifting snow at low elevations in E. Fork. Snow intensity diminished on the drive back to Hailey around 2 PM.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
10 E. Fork Big Wood
N 6,000
D1.5 SS S-New Snow N-Natural Poor visibility. I couldn't see above 6,000'.
Numerous slab avalanches spanned most low elevation, N-facing terrain above the E. Fork of the Big Wood River.

Snowpack Observations

Greenhorn, 5,800', N:
130-60 F/F-, Storm snow
60-58 4F, (1/13) MFcr, fragile and heavily faceted. Responsible for cracking and collapsing.
58-35 F, facets
35-30 4F, (12/11) MFcr.
30-GR F-, depth hoar

Storm snow accumulations have settled to 70 cm (28 in) in this low elevation location. This slope cracked and shifted downhill after a collapse I triggered from at least 150' away.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
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: 70 cm/ Jan. 26
Comments: Weak melt freeze crust with facets above and below. No surface hoar found. Rose is shaded where problem was observed.

Terrain Use

I avoided avalanche terrain.