Today’s new snow will be adding 1-2″ of SWE to the upper snowpack. This will be adding a lot of stress to buried persistent weak layers, and there will also be weak interfaces within the new storm snow. Natural and human-triggered avalanches are likely today. Avoid terrain 28-degrees and steeper. This is a bad day to venture into avalanche terrain. Smaller slides will be likely to step down to deeper weak layer, causing wide propagation.

Confidence: High. Distribution: Widespread in openings and alpine bowls. We have a new buried persistent weak layer (the New-Years Surface Hoar and Near-Surface-Facets) lurking about 3 feet deep underneath the new snow. This will be the primary concern this weekend as it has been steadily loaded and is ripe for a trigger. This weak layer is tricky and likely lurking in steep terrain, rollovers, and wind loaded areas. Today’s new snowfall is adding a lot of stress to these deeper weak layers, creating a dangerous situation.

Avoid avalanche terrain today. Even small slides can kill, especially when they run into terrain traps. In times of high danger, route-finding skills are essential. Be careful not to expose your group to steep openings, even if they are small.

(Surface hoar near-treeline in the Transitional Zone 12/31. Once buried by wind slab or new snow these feathery crystals become a dangerous persistent weak layer that will require extremely careful assessment and overall immediate avoidance in avalanche terrain. Photo: Tim Thomas)

Confidence: Low. Older weak layers from November-December are now buried deep enough that the likelihood of triggering one of these deep slab avalanches is unlikely. Remember that shallow or thin areas in the snowpack could be ripe for access to these deep instabilities, especially above treeline where the snowpack is generally thinner than mid-elevations. Travel where the snowpack is fat and make assessments where it is not. This will help save some time digging. Think about how upper layers over the terrain could communicate to layers deeper in the snowpack. Minimize exposure, use terrain wisely, avoid excess time in run-out zones, practice safe travel technique and remember how your decisions effect yourself and others.

(This is a example of a deep slab avalanche trigger by a cornice fall from several years back. Notice how the slab stepped down to deeper layers and communicated between two shallow rock terrain features. Remember to imagine how the three-dimensional snowpack covers the underlying terrain. Photo: Tim Thomas)