Pro Field Report
Basic Information
Observation Details
Observation Date:
January 28, 2023Submitted:
January 29, 2023Observer:
SAC - VandenBos (off duty)Zone or Region:
Banner SummitLocation:
Copper (6,700-9,000, primarily northern half of compass)Signs of Unstable Snow
Recent Avalanches?
None ObservedCracking?
IsolatedCollapsing?
IsolatedSnow Stability
Stability Rating:
GoodConfidence in Rating:
ModerateStability Trend:
SteadyAdvanced Information
Weather Summary
Cloud Cover:
OvercastNew/Recent Snowfall:
12-15cm at highway, 15-20cm at upper elevationsGenerally overcast skies with some short windows of veiled sunshine in the afternoon. S-1 tp S1 snowfall for much of the afternoon with just a few cms of accumulation. Light winds with moderate gusts blowing out of the W/NW on top and within about 700-800' of the summit. Calm winds below.
Avalanche Observations
A skier (?) had stomped along the cornice above the north side of Copper and produced a small windslab that extended 8-10 m along the slope, just below the cornice, but only a meter or two downslope. This looked like it had just stalled out a short distance downslope. I did not observe any recent natural avalanches, though visibility was largely limited to the terrain I was in.
Snowpack Observations
I dug 3 pits to look for 1/5 surface hoar and to look at nature of more recent storm interfaces. These pits were in sheltered, partially treed terrain between 7,500-7,800'. The 1/5 interface was down 45-50cm. This layer produced ECTNs with hard force or ECTXs in all of my pits. SH had been laid over in these pits, though the fracture plane was disconcertingly clean, with FCsf + SH shards on top of a stiffer surface below. I think we are headed in the right direction with this problem but I'm not ready to write it off yet. I also found some small, standing SH on top of FCsf at the new old interface down 15-20cm. This produced ECTNs in the 2-4 range. The fracture plane was relatively rough.
Lots of evidence of the past week's wind event, with stiff, slippery, hard slabs in lots of exposed middle elevation terrain. Most of these were unreactive but a few produced small, localized collapses. In sheltered lower and middle elevation, the new snow had not been affected by the wind. In exposed upper and some middle elevation terrain much of the new snow had been pushed around by W/NW winds, forming soft, 20-40cm thick drifts leeward to the wind. A very small skier-triggered pocket of wind slab had released above the north face of copper earlier in the day.
Avalanche Problems
| Problem | Location | Distribution | Sensitivity | Size | Comments |
|---|---|---|---|---|---|
Persistent Slab
|
|
Layer Depth/Date: 45-50cm Weak Layer(s): Jan 5, 2023 (SH) Comments: Rose shaded based on where I looked for this layer in snowpits today. Sensitivity observed in these pits was between stubborn and unreactive. |
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Wind Slab
|
|
Layer Depth/Date: down 20-40 cm |