Sawtooth Avalanche Center

Pro Field Report

Basic Information

Observation Details

Observation Date:
December 21, 2021
Submitted:
December 21, 2021
Observer:
SAC - Davis
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
Wells Summit

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
Isolated
Minor cracking in wind drifts since Sunday's ~4-5 inches. One large collapse on a NE facing slope at 7,800'.

Snow Stability

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

Bottom Line

Where old snow (prior to December 11th) exists, I experienced collapsing and observed unstable snowpack test results. I would not have skied similar 35* slopes. Old snow extent may be broader in distribution than in the WRV as I suspect it extends to lower elevations. Given the structure, test scores, and collapsing I'd expect natural avalanche activity with a decent load of new snow later this week.

Media/Attachments

Remnants of avalanches that failed during the prolonged storm event that began on December 11th. Avalanche debris is visible below the main chutes. It also looks like at least one slab pulled out below a mid-slope rock band, potentially triggered from above. Soldier Mountains. 9,400' E.
Persistent slab avalanche on a E/ENE facing slope at 8450' on Peak 2 in the Soldier Mountains.
Snowpit near Wells Summit. NNW-facing slope at 8,000'.
https://www.youtube.com/watch?v=CLbf4MGmtVw&t=4s

Advanced Information

Weather Summary

Cloud Cover:
Clear
Temperature:
0-25F
Wind:
Light , W
New/Recent Snowfall:
10 cm HST (12/19)

0F in Fairfield and 18F at Wells Summit TH. Light W wind, no blowing snow. High clouds increased late in the afternoon.

Avalanche Observations

The only avalanches I could make out with any certainty are those in the images below. I sat and glassed for quite some time, took photos, and looked closely at them on the computer. I feel that I would have seen a slide similar to the one on Peak 2, as that crown was still easily visible. That said, it's been windy, snowing and it was a multi-day storm, so I'm sure there were slides that went undetected.

Snowpack Observations

The snowpack depth in this area is sufficient to cover sage and rocks beginning at about 8,000' (a little lower on shaded aspects). Based on limited obs, it looks like old snow exists lower in elevation on shadies here than in the WRV. The 12/11 storm did not produce as much snow here as compared to the WRV with slabs ranging from 20-45 cm (sunny-shaded) at 8,000'.

Pit image and test results can be seen in the image. Generally a soft F-4F slab sits on the ground or old snow (3mm FC above a crust). Where old snow exists I got unstable snowpack test scores and experienced collapsing.

There were very few off-trail tracks except near the Corrals and NE of Wells Summit in areas that are generally open, smooth, and heavily traveled. We're one good storm away from widespread off-trail riding.

Snowpit near Wells Summit. NNW-facing slope at 8,000'.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Persistent Slab
Isolated
Specific
Widespread
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
Layer Depth/Date: 40-60 cm
Weak Layer(s): Dec 11, 2021 (FC)
Comments: Estimated for the Soldiers based on early season snow and limited obs.

I encountered 1' drifts from recent (12/19) snow and wind. These were confined to the upper 40' of ridgetops. I'd imagine you'd encounter more of these at upper elevation.

Terrain Use

I would have felt comfortable in avalanche terrain lacking snow prior to 12/11. I planned to avoid avalanche terrain where old snow existed and happily stuck to that plan.