Professional Field Report

Basic Information

Observation Details

Observation Date:
January 14, 2020
Submitted:
January 14, 2020
Observer:
SAC - Davis
Zone or Region:
Soldier and Wood River Valley Mtns
Location:
Indian Creek - Etna

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Widespread
Collapsing? 
Isolated
No fresh avalanches were observed from this last round of snow and wind (Monday night into Tuesday) although I experienced cracking in fresh wind slab as well as on Dec 7th surface hoar buried 48 cm deep. One collapse failed ~40' in radius on a wind slab comprised of snow since Jan 10th.

Snow Stability

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

Bottom Line

I observed freshly formed wind slab (formed last night and today) as well as older wind slab from Sunday night's wind + snow. Sunday's storm built slabs further down into the valley bottom. The extent of this wind-loading was a bit obscured by last night's snowfall but evident underfoot. Today's drifting was more relegated to exposed middle and upper elevation. The thickness of these recent wind slabs has doubled the snowpack depth in this area. I was able to produce shooting cracks in both wind-loaded and sheltered terrain.

Media/Attachments

Small, freshly formed wind slabs (formed Monday night and Tuesday) were touchy in exposed middle elevation terrain on Tues, Jan 14.
December 7th surface hoar was still present. This was on the underside of one of the blocks that failed in an ECT. Although easily visible in the pit, the surface hoar has greatly deteriorated by secondary faceting processes.
Surface hoar (top) and facet (bottom) sandwich just below recent storm snow.
Snow cover in Indian Creek on a 8,200' ENE facing slope. New snow since (1/10/20) comprises roughly half the snow depth.

Advanced Information

Weather Summary

Cloud Cover:
Partly Cloudy
Wind:
Moderate , SW

Only a few clouds to begin the tour, then I was in a whiteout (blowing snow and clouds) midday before clearing again in the afternoon. Clouds increased into the early evening.

Snowpack Observations

@8200, ENE, HS=78cm, HST=30cm (since 1/10), HN24=15cm:
Problem layer was (12/7) surface hoar sitting on a pile of rotten F and F- facets to the ground. ECTP 23 and 27, PST 25/100 End down 48 cm.

There was also a complex 10cm layer of facets and surface hoar above 12/7. Not positive on dates. ECTN's and PST 33/100 Arr.

Snow cover in Indian Creek on a 8,200' ENE facing slope. New snow since (1/10/20) comprises roughly half the snow depth.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 20-40 cm
Comments: There were two generations of wind slab, but most were no harder than 1F-. Last night's wind slabs were sensitive today but I expect that problem to heal quickly. Multiple loading directions, cross-loading and drainage wind built slabs on many middle and upper elevation slopes. Wind-loading today was initially from the SW and shifted W and N upon exit. Although wind-loading is apparent on low elevation slopes in the WRV, these pockets were isolated in Indian Creek.
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: 30-60 cm
Comments: No matter the aspect, there were weak F or F- facets and depth hoar at the ground. Dec. 7th surface hoar was the layer of concern in my pit, but multiple hand pits on Dec. 7th in the absence of surface hoar produced easy, clean shears. Cracking on this interface was widespread in windier and sheltered locations.

Terrain Use

I steered clear of any avalanche terrain that showed obvious wind affect.