Professional Observation

Observation Details

Signs of Unstable Snow

Key Points

We went to watch some wet loose avalanches slide in steep southeast-facing terrain and track surface faceting. Wet loose were minimal, surface facets were notable. Also, the wild card: glide cracks.

• We saw a few very small wet loose avalanches and some minor rollerball activity by mid-afternoon at middle and lower elevations. While skinning up the moraine we got isolated cracking in some very small wind drifts. We saw no other signs of instability.
• There’s a glide crack opening on an east-facing slope on Mono Jim Peak, and 4 gaping on the southeast slopes of Mt. Morrison. All of these are at about 10,000 feet. They are all in areas with smooth ground cover (slick rock slabs). They look like dark, upside-down crescents where the whole snowpack has opened to reveal the wet ground underneath. There’s often wrinkled snow down slope. Glide cracks can open mid-winter for several reasons. They can fail as full-depth avalanches, seemingly without warning. Or they can just melt in place. The important things to know are that they are more likely to fail during periods of rapid or prolonged warming (or rain), and they’re easy to avoid.  Just stay out from under the brown frowns.
• Despite balmy air temps, the snow surface on northerly slopes stayed dry and cold. The snow from the 1/29-1/30 slider is faceting atop variable crusts. The snow under the crusts is also faceting – even where the snowpack is deep. Think about how warm and wet a lot of the early January storms were. That water and heat have been stored in the snowpack and now, with colder and drier-than-normal weather, water vapor is rising through the more recent snow, turning it to sugar. Fun, sluffy snow now/a possible persistent weak layer once it’s buried.