Northwest Avalanche Center

Observation: Public

All Observations

Observation Details

Name:
Andy Harrington
Observation Date:
February 19, 2021
Submitted:
February 19, 2021
Zone or Region:
West South
Activity:
Skiing/Snowboarding
Location:
Cement Basin

Observed Avalanches

Did you observe any avalanches? 
Yes
Avalanche Type:
Hard Slab
Size:
Size 2: Could bury, injure, or kill a person
Elevation:
6400'
Aspect:
NE
Comments:
Crown was a day or maybe two old, so likely occurred on 2/17-2/18. Was close to 2 feet deep and was on a steep unsupported rocky slope.
Photo:

Signs of Unstable Snow

None reported

Observations

Traveled up East Peak and down into Cement Basin to dig around and look at our layers of concern heading into the weekend and another atmospheric river event.
Found a slight breakable crust on slopes with a southerly tilt that receive direct sunshine. Closer to the ridgeline, there were areas of wind-stiffened snow and a few drifts that produced some cracking as I skinned. East aspects on the lee side of the ridgeline had somewhat freshly built cornices and some wind-loaded slopes just below them.

Dug around 6200' on a NE aspect down in Cement Basin. HS was 237. Found that the 2/11 was ~67cm down, with another layer ~59cm down. These two layers produced inconsistent results, taking turns breaking CTH. Most of the failures on the lower layer (2/11) were sudden and planar. Both layers had some faceting stellars, with the 2/11 being more pronounced. ECTs and PSTs did not propagate a failure on either layer despite some failures on the 2/11.

The Mid-January crust was down 123cm and still contains 0.5-1mm facets above the crust. Within and below the crust, there are larger facets, and the snow is very rotten. Deep Tap Tests produced sudden and planar failures on the 22 tap.

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