Professional Observation

Basic Information

Observation Date:

December 30, 2021

Submitted:

December 31, 2021

Observer:

Steve Mace | ESAC Forecaster

Zone or Region:

Lee Vining

Location:

V bowl area

Recent Avalanches?

Yes

Cracking?

Isolated

Collapsing?

None Experienced

Significant wind transport was occurring today at all elevations leading to sensitive wind slabs ranging in size, distribution. Shooting cracks were quite common today and I found fresh wind slabs to be easily triggered. Shallow wind deposits 4-8″ in depth were specific in distribution and observed on the leeward sides of ridgelines, cross-loaded gully features, and mid-slope terrain features even at lower elevations. Thicker deposits ~18″ were more isolated in distribution and observed on more typical catchment zones adjacent to ridgelines. I did not travel into the alpine today however I would suspect more sublimation that deposition was occurring at the higher elevations.

I dug a pit at about 9800′ on a NE aspect near treeline today. The height of snow in this location was 165cm and overall I found the snowpack to be well bonded for the most part and quite right side up in this location. Although, I did find sensitive wind deposits on the surface and faceted weak snow at the base of the snowpack. Stability tests confirmed both of these to be layers of concern. Compression tests and extended column tests failed on isolation in the new wind deposits and both were reactive on the lower facet layer. (CT21 @20cm, ECTP 26 @20cm) Honestly, I was a bit surprised to see failure in the facets at all given the depth of the test.

Stability Rating:

Poor

Confidence in Rating:

High

Stability Trend:

Worsening

Advanced Information

Cloud Cover:

Mostly Sunny

Temperature:

Wind:

Extreme , SW

Low valley cloud cover made seeing the alpine difficult from 395 this morning however, mostly clear skies prevailed once you got above. winds picked up substantially throughout the day reaching gale force speeds near and above treeline by early afternoon. Impressive amounts of flagging could be seen along the Dana plateau and off the surrounding high peaks throughout the day. Temperatures remained below freezing and the strong winds kept it feeling quite brisk.

Surface conditions were variable today and mostly dependent on how much wind the snow had seen. More exposed areas ranged from thinning areas of soft snow to hard wind board and large sastrugi while more sheltered areas were still holding significant amounts of low-density powder, albeit wind textured in areas. I suspect the variable nature of the snow will continue to intensify as today’s strong winds continue.