Pro Field Report

Basic Information

Observation Details

Observation Date:
February 4, 2021
Submitted:
February 4, 2021
Observer:
SAC - Chris Lundy
Zone or Region:
Banner Summit
Location:
Copper (6700-8800')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced
Avalanche refers to one reported yesterday.

Snow Stability

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

Bottom Line

Buried surface hoar seems to be relatively widespread in the Banner Summit area beneath 2' of recent storm snow. It was responsible for a new avalanche yesterday (likely remotely-triggered) and produced poor snowpack test scores.

Media/Attachments

Buried surface hoar layer on Copper Mountain. The slab is on the top, and there are some small facets below the surface hoar.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Temperature:
cold
Wind:
Light , NW
New/Recent Snowfall:
20-25cm HST since 2/2, 1-2cm fell yesterday

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Feb 3, 2021
(Exact) 		South of Copper
NE 8500ft 		D1.5 SS-Soft Slab I-New/Old Interface 2ft U-Unknown
This avalanche failed 2' deep on buried surface hoar. This weak layer has presented itself as surface hoar in some areas and small facets in others. NE, 8400', Copper Mtn.
This avalanche failed 2' deep on buried surface hoar. This weak layer has presented itself as surface hoar in some areas and small facets in others. NE, 8400', Copper Mtn. Photo: Sawtooth Mountain Guides
Report
South of Copper

Snowpack Observations

7100', N: HS 175cm. 1/27 = strengthening FCsf on top of rain crust, 50cm down. No SH found and this is usually a favorable location. ECTX.

8000', W: HS 200cm. HST 25cm from 2/2-3. 1/27 = 3-5mm SH on 5cm layer of FCsf, 60cm down. ECTP25. See photos. It seemed that the SH was responsible for the ECT fracture vs the FCsf. 12/11 was probed to be 150cm deep.

8000', W: ECTP25 60cm down on 1/27 SH.
Buried surface hoar at the failure layer of an Extended Column Test. The ECT propagated on 25 taps, and you can see the block displacement. 8000', W on Copper Mountain.

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: 60cm
Weak Layer(s): Jan 27, 2021 (FCsf)
Comments: Rose painted based on observed terrain.
Deep 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: 150cm
Weak Layer(s): Dec 11, 2020 (FCsf)
Comments: Rose painted based on observed terrain.

Terrain Use

I avoided avalanche terrain