Pro Field Report

Basic Information

Observation Details

Observation Date:
December 31, 2021
Submitted:
December 31, 2021
Observer:
SAC - Chris & Sara Lundy
Zone or Region:
Banner Summit
Location:
Cape Horn Ridge (6700-8900', S-E-NE)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Snow Stability

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

Bottom Line

October weak layer is buried 4-5+' deep in mid to upper elevation terrain. The weak layer is "protected" by a very dense slab is and is beginning to show signs of strengthening and compaction - in other words, it's becoming very difficult to trigger - but the possibility exists in very steep, rocky, wind-affected terrain. We found no sign of newer weak layers in the top 3 feet of the snowpack.

Media/Attachments

Already seeing some mid-elevation cornices pulling away. Seems too early for this!

Advanced Information

Weather Summary

Cloud Cover:
Obscured
Temperature:
singe digits
Wind:
Light , NW
New/Recent Snowfall:
25-30cm low density HN24

Cloudy, cold, and S-1 during our tour - perhaps 1cm of accumulation. A few openings in the clouds were visible in Stanley around 4pm, but it was still snowing lightly on and off.

Snowpack Observations

Primary objective today was looking for midpack weak layers found in the southern part of the forecast area, and assessing depth of the slab over 12/11. We dug 3 pits at low, middle, and upper elevations and did not observe any sign of prominent weak layers in the top 1m - ECTX's across the board.

@6830', ESE: HS 120-140cm. Did see a visible layer 1m down (12/22? I.F.) but ECTX.

@8200', ENE: Prime forest window for SH growth. HS 195cm, 12/11 probed at 120-140cm. No obvious layers and ECTX in top 1m. 1m tall ECTP block tipped into pit intact/no shears.

@8850', E: HS 215. 12/11 down 160cm (see photo) and 1F hard - definitely showing signs of getting "squashed". Bottom 90cm of slab is P. ECTX in top 1m.

In this photo, a 185cm tall forecaster is standing on the 12/11 weak layer next to a 160cm slab.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Deep Persistent Slab
Isolated
Specific
Widespread
 Unknown
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 130-160cm
Weak Layer(s): Dec 11, 2021 (FC)
Comments: No tests performed. Tempted to call it unreactive, but little data to base that on.

We were in fairly sheltered terrain and did not observe a wind slab problem. Effects from yesterday's wind was masked by new snow.

Terrain Use

We avoided avy terrain where October snow existed. Would have felt comfortable on most solar slopes as long as it wasn't wind loaded.