Sawtooth Avalanche Center

Public Field Report

Observation Details

Observation Date:
December 14, 2019
Submitted:
December 15, 2019
Zone or Region:
Banner Summit
Activity:
Skiing/Snowboarding
Location:
Copper

Observed Avalanches

Did you observe any avalanches? 
Yes
Avalanche Type:
Soft Slab
Size:
Size 1: Relatively harmless to people
Elevation:
Copper Summit - 8966'
Aspect:
N
Comments:
Similar to previous observations by SAC. Crowns were visible from the summit of Copper proper on North facing slopes. North steep rocky slopes appeared to have cycled again on the same bed surface as previous observations.

Signs of Unstable Snow

Did you see shooting cracks? 
No
Did you experience collapsing or whumpfing? 
Yes, Isolated

Observations

Pretty great weather out at Copper on Saturday. Clouds were present with light snow in the morning, turning to cloudy with spots of sun.

Checking out a different entrance we walked a west facing ridge to one of the high points of Copper. Navigation was easy due to good visibility and the remnants of last weekend's skin track. We didn't observe any surface hoar formation from previous nights and snow seemed relatively settled in the valley.

Once we cleared the ridge at about 8,000 feet isolated whumps were observed when traveling away from the ridge or the skin track. Poked into an open west face just beneath the high point to dig a pit and assess any interesting wind deposits on the weak snow pack. Density of snow did feel more wind effected with a consistent density between the two recent storms.

Pit Details

West Facing 25 Deg Slope
Elevation: 8770'
HS - 105 cm

0-30 cm DH
40 cm SH layer from Dec. 7th
40 - 65 Dec. 7th weekend Storm
65-105 PP Dec 11/12 storm

Stability Tests
CT 7 - compressed recent new snow
CT 12 - at 30 cm DH

ECTP 12 Q1 - at 30 cm DH
ECTP 18 Q1 - at 40 cm SH layer

Stability results kept us out of open terrain and off any slopes over 30 degrees. Persistent weak layers at the bottom of the snow pack make for an interesting mixture of sensitivity. Step down avalanches appear to be a possible scenario as these weak interfaces take on more snow.

Advanced Observations

Observed Avalanche Problem #1: 
Persistent Slab
Comments: