Pro Field Report

Basic Information

Observation Details

Observation Date:
February 25, 2021
Submitted:
February 25, 2021
Observer:
SAC - Ethan Davis
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
Salt Bowns Ridge (All aspects, 6,000-8,500')

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
Isolated
Collapsing? 
None Experienced
Cracking in sensitive thin (<30 cm) drifts where they sat above Monday's sun/temp crust.

Snow Stability

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

Bottom Line

Sensitive, thin wind deposits sit above Monday's crust. This setup seems the most likely candidate to be problematic with tomorrow's loading, followed by slick, icy crusts on steep, sun-exposed slopes.

Media/Attachments

These large drifts all along the Salt Bowns road give you an idea of what the middle elevation wind-loading looked like over the past 10 days or so. Roughly the upper third of these drifts were recent.
Looking west toward the Soldiers. Strong to extreme north wind has striped many N-facing knolls at middle elevation. Some mid-slope drifts had formed in unusual locations.
This was just one example of a crust I found at the snow surface. The facets (top of block in this picture) were on the underside of a 2" thick knife hard melt-freeze crust on a steep SW-facing slope at ~8,500'.

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Temperature:
upper-teens F
Wind:
Moderate , NW
New/Recent Snowfall:
A couple of inches since Monday's warmup.

Overcast skies by 10:00 AM. Wind was light at middle elevations until about 11:00 AM then plumes of blowing snow were observed along the Soldier Crest and in exposed middle elevations. Only a few flakes fell while I was there but snow appeared to start in the W. Smokys as early as 11:00 AM.

Avalanche Observations

I had a good view of the Soldiers and saw no sign of recent avalanche activity. I did see a few medium-sized cornice breaks at upper elevations, but they did not initiate a slab.

Snowpack Observations

The snowpack here is highly variable. Elevations up to ~7,500' held a substantial ambient temp melt-freeze crust at the surface. Above this, stout crusts continued up to and beyond 8,500' on steep, sunny slopes. All of these crusts had facets associated with them. Shaded slopes above 7,500' were "crust free" near the surface but starting to facet as well.

Most slopes have seen extensive wind sculpting. Stiff slabs exist near the surface and in the mid-pack on most slopes. Facet layers were very well developed in more sheltered terrain both in the middle of the snowpack and near the ground.

N-facing, 8,400', HS = 150 cm:

150-135 F, DF
135-124 4F, FC ---ECTN28 down 26 cm (2/11?)
124-70 F+ to 1F, FC
70-40 4F
40-39 Decomposing crust
39-10 F, DH (3 mm), dry December facet layer
10-0 4F-, DH

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 20-70 cm
Comments: There were 2-3 generations of wind slab that looked to have formed over the last 10 days. The older slabs were anywhere from 4F to 1F+ and up to 70 cm thick. These broke when pulling on the block but were stubborn where I found them. A thin layer of wind slab (<30 cm) was touchy where it sat atop Monday's temp/sun crust.

Both of these layers also sit on PWL's, so I suppose you could call them persistent slabs. I'd guess that additional loading on the shallower fresh slabs over the crust will behave more like a persistent slab if this storm materializes.

Terrain Use

I avoided avalanche terrain.