Pro Field Report

Basic Information

Observation Details

Observation Date:
January 1, 2023
Submitted:
January 8, 2023
Observer:
SAC - Preuss, VandenBos
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Mushroom/Galena Peak (W-S-E; 7300-9800')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Isolated
We experienced one large collapse and shooting cracks in a recently wind-loaded slope near the middle and upper elevation transition area going up Galena Peak.

Snow Stability

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

Bottom Line

We were able to intentionally trigger a large Wind Slab avalanche from the ridgeline. Winds today were cross loading NW gullies and south facing slopes. These areas proved to be most sensitivity to the weight of a skier with signs of instability in the form of cracking, collapsing, and triggered avalanches large enough to bury you. The recent human-triggered avalanche on Mushroom Ridge failed on a weak layer of sugary facets sitting on top of a firm crust.

Media/Attachments

Ben intentionally triggered a Wind Slab from the ridgeline. It broke 1-2' down with a stiff slab and resulted in an avalanche large enough to bury you.
Crown profile of human-triggered avalanche on Mushroom Ridge. This avalanche failed on a thin layer of facets above a firm crust. It is unclear where this was remotely triggered from as there were multiple parties out in this area.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Wind:
Moderate , N

Clouds clung to the tops of the Boulder Mountains today. Everywhere else show sunny skies with large plumes of moving snow at ridge-lines. Wind varied from N-NE depending on the terrain features around us. We could feel the wind down to the valley floor.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Jan 1, 2023 4:20 pm
(Exact) 		Galena Peak
N 9600ft 		D2 I-New/Old Interface 1ft AS-Skier
c-Intentional 		Report
Galena Peak

Ben investigated the crown of the remotely triggered avalanche on Mushroom Ridge. He found the failure point was a thin layer of facets (12/19) sitting on top of a melt-freeze crust. The area around the start zone was recently wind-affected. The winds cross-loaded this slope and likely was a contributing factor to the release of this slide. There was evidence of the snow drifting into the crown from the looker's right side. This slide ran down through trees, into a gulley, and crossed over recent tracks from a nearby run.

Snowpack Observations

We dug in Senate Creek on a WNW aspect at 8500'. The mid-pack weak layer (12/19) was a thin strip of near surface facets that was unable to show propagation results (ECTN23) down 40cm.

The bottom of the snowpack consisted of basal facets (11/27) cupped with striations. There are signs of that layer healing with some rounded edges and increasing hardness (4F-/F+). It produced hard results with ECTP26, 33, 38 down 80-90cm.

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 19, 2022 (FC)
Comments: Rose shading reflects the terrain where we found this problem today.
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: 40cm

South facing slopes with the crust/facet combo (12/19) are reactive with recent wind-loading. The 12/19 layer was a recent player in the remote triggered avalanche on Mushroom Ridge. The varying depth of the crown showed the wind may have aided in overloading the weak layer.

Terrain Use

We left the field Stepping Back from the increased winds causing sensitive Wind Slabs.