Sawtooth Avalanche Center

Public Field Report

Observation Details

Observation Date:
December 20, 2020
Submitted:
December 22, 2020
Zone or Region:
Banner Summit
Activity:
Skiing/Snowboarding
Location:
Cu

Observed Avalanches

Did you observe any avalanches? 
Yes
Avalanche Type:
Wet Loose
Size:
Size 3: Could bury and destroy a car, damage a truck, destroy a wood frame house, or break a few trees
Elevation:
Middle
Aspect:
NW
Comments:
Driving down Canyon Creek I observed a large, what appeared to be a natural avalanche in the burn area north of Zumwalt that dammed the creek. Multiple small avalanche debris piles along the west side of the highway also in the usual roadcuts. d

Signs of Unstable Snow

Did you see shooting cracks? 
Yes, Isolated
Did you experience collapsing or whumpfing? 
Yes, Isolated

Observations

We climbed to the west corner of the Tube just above Jacks and observed what appeared to be a natural release due to cornice fall into the north ridge probably failing on layer of facets. Did not appear that this went far, but didn't get too close to get a good look.
Skied to upper Jacks near the rock, dug a pit and got some unsettling scores on stability testing. (see above)
Traversed back to the ridge and skied Bruces. Climbed back up to standard skintrack from the bottom of Bruces and then skied south from the lunch tree. No instabilities noted or tested on this slope, still very thin in places. Some minor snow cracking noted near creekbed. SW facing ridge to the east produced some shooting cracks on crust/facet layer above creekbed.
Warming temps with continual snowfall throughout the day and steady wind in open terrain from WSW at moderate speeds.

Thanks for leaving the road open for us, ITD.

Advanced Observations

Observed Avalanche Problem #1: 
Storm Slab
Comments: 
Made multiple observations in the snowpack on the way up the ridge. In the trees, no apparent signs of instability.
Steady snow at S1 and moderate winds out of WSW. Multiple handpits along the route all showed a new soft storm slab forming on top of a thick layer of facets about 20 cm down.
Dug a pit near the rock on Jacks and got scores that were expected. No cracking or instabilities noted while skiing down to snowpit location. Minor whoompf noted on ridge between Jacks and the face while setting skintrack.
HS = 80 cm/4F down to 35cm then a thick layer of facets at least 15 cm deep, sitting on top of a decaying crust.
CT1Q1 at 35cm down
ECT7/8@35cm down.
Observed Avalanche Problem #2: 
Wind Slab
Comments: 
See above, due to location of snowpit windslab was also probably factoring into stability test results.