Confidence : High Distribution: Widespread. Today’s new snow will be adding 1-2″+ of SWE to the upper snowpack that started cold and will end warm, an up-side down setup. This will be adding stress to any buried persistent weak layers further down. There will also likely 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 could step down to deeper weak layers, causing wide propagation.

Confidence: Moderate to High. Distribution: Isolated to Widespread. We have two primary layers of concern:

1. Melt-freeze crust from 1/10 down 60-80cm in elevations up to ~3000′
2.  New-Years Surface Hoar and Near-Surface-Facets interface about 100-120cm down in protected areas near tree-line, steep openings and alpine bowls.

Observations are limited. It is uncertain how these layers will react to the new load. These weak layers are tricky and could produce large avalanches with recent rapid loading of the new snow, especially in steep terrain, rollovers, and wind loaded areas. Today’s new snowfall, rain on snow, and strong south winds are adding a lot of stress to these deeper weak layers, creating a dangerous situation.

(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)