Pro Field Report

Basic Information

Observation Details

Observation Date:
February 6, 2021
Submitted:
February 6, 2021
Observer:
SAC - Chris Lundy
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Prairie Peak (7000-9300', SE-E-NE)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced
See avalanches below - one new natural on Galena Peak and one triggered wind slab avalanche.

Snow Stability

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

Bottom Line

NW winds were actively loading upper elevation ridgelines. While beginning my descent, I unintentionally remotely-triggered a small(ish) wind slab avalanche. The late-January weak layer was discernible in two different snowpits about 2' deep but did not produce any results during snowpack tests.

Media/Attachments

Small slab avalanche between Prairie and Owl Creek. Looks a few days old, but difficult to say with any certainty. 8300', SSE.
This small wind slab avalanche was remotely-triggered from a point on the ridge about 50 feet away. It broke about 1.5 feet deep and 30 feet wide. The SE-facing slope above Prairie Creek was being actively loaded by the NW wind when the slide occurred.
https://youtu.be/kW93Y-AemGE

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Wind:
Moderate , NW
New/Recent Snowfall:
Seemed like around 5-7cm settled HN from yesterday

Winds were regularly gusting to strong. Skies around the Galena Summit area were BKN until they became OVC midafternoon. Looked sunny in the Wood River Valley. On the drive home, the Sawtooths were full socked in and there were a few snow flurries in the Sawtooth Valley.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Feb 6, 2021 2:00 pm
(Exact) 		Prairie Peak
SE 9300ft 		D1 HS-Hard Slab 1.5ft AS-Skier
r-Remote
This small wind slab avalanche was remotely-triggered from a point on the ridge about 50 feet away. It broke about 1.5 feet deep and 30 feet wide. The SE-facing slope above Prairie Creek was being actively loaded by the NW wind when the slide occurred.
Report
Link
1 Feb 5, 2021
(+/- 1 day) 		Galena Peak West Ridge
NW 9900ft 		D2 N-Natural Report
Prairie Peak
Galena Peak West Ridge

I also observed a very small natural wind slab just next to the one I triggered, as well as a D1 persistent slab in mid-elevation, sheltered terrain (see photo).

Snowpack Observations

HS at lower elevations (7000') was around 1m. 12/11 could be felt with a ski pole about 80cm down.

@7900', NE: HS 140cm. 12/11 down 105cm, still weak and dry. 1/27 down 55cm and presented as subtle FCsf. ECTX in top 90cm even with very hard hitting.

@9000, NE: HS 170cm. 12/11 seemed to be down around 110-130cm - the wind exposure of this slope may have produced variable slab depth. No tests on 12/11. 1/27 was 65cm down and was a thin layer of FCsf with small 3mm SH. ECTX (x2) even with very hard hitting. Very hard loading steps brought out a propagating result (x2) about 85cm down - maybe 1/13?

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: up to 60cm
Comments: Triggered wind slab...
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: 60cm
Weak Layer(s): Jan 27, 2021 (FCsf)
Comments: Multiple ECTX's in two pits. Rose indicates observed terrain.
Deep Persistent Slab
Isolated
Specific
Widespread
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 80-130cm
Weak Layer(s): Dec 11, 2020 (FCsf)
Comments: No tests performed or new information. Rose indicates observed terrain.

Terrain Use

I avoided avalanche terrain except for a few small/inconsequential slopes in the low 30s.