Pro Field Report

Basic Information

Observation Details

Observation Date:
December 28, 2021
Submitted:
December 28, 2021
Observer:
SAC - Davis
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
Warm Springs Ck, Shaw (6,500-7,900, Primarily S-SE-E-NE)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced
Small loose snow, midstorm instabilities.

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
Low
Stability Trend: 
Improving

Bottom Line

There was an overall lack of obvious, large slides from late in the storm. I did not find any concerning results at the recent storm interface (since 12/22) or within the storm snow. The weak snow at the ground on shaded middle aspects is still spooky, but is now >120 cm down and is harder to impact.

Media/Attachments

(12/28/21) NNE aspect at 7,900' (HS = 155 cm). There was about 70 cm new snow above 12/22, and 125 cm above 12/11. There were dirty shears (ECTNs) in the upper 60 cm but nothing concerning. CPST 45/125 END on 12/11.
(12/28/21) NNE aspect at 7,900' (HS = 155 cm). CPST 45/125 END on 12/11.
(12/28/21) On a SE aspect at 7,400' (HS = 130 cm) There was 60-70 cm new snow since 12/22. The only noticeable layer was a 1 cm crust down 70 cm. ECTNs.
(12/28/21) Middle elevation wind affect along Warm Springs Ck Drainage.
(12/28/21) Middle elevation wind affect along Warm Springs Ck Drainage.

Advanced Information

Weather Summary

Cloud Cover:
Partly Cloudy
Temperature:
Single Digits F
Wind:
Moderate , N
New/Recent Snowfall:
HST = 60-70 cm since 12/22

Periods of mostly clear skies. Passing mid and high clouds produced S-1 with no accumulation. N and NW wind was transporting snow along the Smoky Mountain crest near Shaw and at the head of Placer Ck.

Avalanche Observations

I had good visibility near the head of Placer Ck, as well as Shaw Pk. I also had good visibility of the mountains along Warm Springs Ck back to Ketchum. I only saw a few small (D1) loose snow avalanches.

Snowpack Observations

I toured middle elevations between 7,000' and 7,900'. On a SE aspect at 7,400' (HS = 130 cm) I didn't find old October snow. The snowpack was well graded from top to bottom (see image). There was 60-70 cm new snow since 12/22. The only noticeable layer was a 1 cm crust down 70 cm (12/19?). ---ECTN12 down 30 cm (x2), ECTN29 down 60 cm (x2).

On a NNE aspect at 7,900' (HS = 155 cm), I again found a well-graded snowpack until the old October snow near the ground (see image). There was about 70 cm new snow above 12/22, and 125 cm above 12/11. There were dirty shears (ECTNs) in the upper 60 cm but nothing concerning. --- CPST 45/125 END on 12/11.

(12/28/21) NNE aspect at 7,900' (HS = 155 cm). There was about 70 cm new snow above 12/22, and 125 cm above 12/11. There were dirty shears (ECTNs) in the upper 60 cm but nothing concerning. CPST 45/125 END on 12/11.
(12/28/21) On a SE aspect at 7,400' (HS = 130 cm) There was 60-70 cm new snow since 12/22. The only noticeable layer was a 1 cm crust down 70 cm. ECTNs.

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: 125 cm
Weak Layer(s): Dec 11, 2021 (FC)
Comments: Shaded based on obs/ avalanche activity from surrounding area. Observed on 7,900' NNE.

Wind was moving snow at upper elevations, likely building sensitive wind slabs. Previous wind has stiffened/drifted exposed middle elevation terrain in this area.

Terrain Use

I planned to avoid avalanche terrain where I suspected 12/11 to exist and stuck to that plan.