Johnson Canyon - Near surface faceting and CT results

Location Name: 
Johnson Canyon
Region: 
Donner Summit Area
Observation Date & Time: 
Tuesday, January 26, 2021 - 11:00
Location: 
39.339780, -120.297000
Is this an Avalanche Observation?: 
No




Observation made by: Educator at Blackbird Mountain Guides

Tabs

Observation
Description of Snow, Weather, and Avalanche Conditions: 

Faceting is softening the upper snowpack, even breaking down melt freeze and rain crusts that had been harder previouslly.  We got interesting results in this pit on a layer that was hard to identify before tests (probably surface hoar, but grains were difficult to ID with a loop).  We got a very clean shear on a single loading step in two compression tests, indicating the potential for initiation in one of our pits on a recent AIARE 1 in Johnson Canyon.  Following up with ECT tests we got ECTN results, indicating what we expected: that an avalanche would have difficulty propagating across a slope.  We also got much less reactive CT tests in our nearby pit, leading us to believe that our first pit was a particularly sensitive spot in the snowpack.

The tests reifnorced the low hazard, but also showed weakness in the upper snowpack that continues to be develop in shady areas sheltered from wind.  Faceted grains that we observed were still not larger than 1mm, but our temp profile shows that there is a significant enough temp gradient to cause growth.

Snowpit or crown profile photo or graph: 
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