Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
January 21, 2021
Submitted:
January 21, 2021
Observer:
SAC - Davis, Savage
Zone or Region:
Sawtooth and Western Smoky Mtns
Location:
Couch Summit, Fleck Summit, S. Fork Boise River (All aspects, 5,500-6,500')

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced
Signs of previous cracking that appeared to occur during the last storm.

Snow Stability

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

Bottom Line

We were surprised by the lack of recent natural avalanche activity. We saw only one middle elevation slab avalanche and no slides at low elevation outside of very small wet loose and one thin slab on a road cut.

Overall snow depth is deeper here on S-facing slopes at 6500' than on N-facing slopes at 9,000' in the Wood River Valley. Crusts, crusts everywhere. This area has seen a good amount of snow and rain. The snowpack holds numerous crusts and shows sign of multiple pushes of meltwater deep into the pack.

Media/Attachments

This small slab avalanche  appears to have failed on the new/old interface during or shortly after the storm on January 13th.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Temperature:
30 F
Wind:
Light , NW
New/Recent Snowfall:
HN = ~1 cm

Broken skies and intermittent, very light snow showers.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
2 S. Fork Boise
E 6500
D1 SS I-New/Old Interface This small slab avalanche appears to have failed on the new/old interface during or shortly after the storm on January 13th. We checked out the failure layer of another, similar small slab which ran just above a weak crust.
This small slab avalanche  appears to have failed on the new/old interface during or shortly after the storm on January 13th.

The lack of low elevation slides was surprising. We had decent visibility in the S. Fork drainage and from Fleck summit up to elevations around 8,500' and saw no avalanches that broke deeper than the new/old interface. Not to say they aren't out there..

Snowpack Observations

The height of snow near Fleck summit is around 70-80 cm at 6,400'. Baldy (Wood River Valley) is showing a height of snow of 60 cm at 9,000'.

A stout rain crust was present at all elevations below 6,500' (our high point) although it was faceting a little in the valley bottom. The (12/11) weak layer was a solid mass of K hard ice on southerly slopes. It has consolidated a bit on E facing slopes but still presented as a 10 cm thick layer of 2 mm F facets which produced propagating results.

SnowPilot profile on Fleck Summit, 6350' E/SE aspect.
SnowPilot profile on Fleck Summit, 6450' south aspect.

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
Weak Layer(s): Dec 11, 2020 (FCsf)
Comments: ECTP20, ECTP21. Not likely a problem on W-S-SE. Rose is shaded where problem was observed.

Terrain Use

We closed off-trail riding in avalanche path runouts and start zones. We stuck to this plan, although avalanches in low elevations were probably unlikely.