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 2 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. You may find relatively stable snow in isolated areas that are more wind-packed, but remember that this weak layer is tricky and likely lurking in steep terrain, rollovers, and wind loaded areas. Strong southeast winds last night will have created fresh wind slabs on N – W aspects, and on cross loaded terrain features. Areas of fresh wind loading will be dangerous and should be avoided.
Keep a wider safety margin than usual, avoid run out zones, and only expose one person at a time to a slope. 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)
Observed avalanche activity over the last week has been mainly small (D2) natural slides in wind-loaded and cross-loaded pockets. Depth of these slides has been roughly 30-60cm. Aspects ranging from East to Northeast to West, elevations 1800-4000ft.
Bottom Line: We have a new buried persistent weak layer (The New-Years Surface hoar and/or Facets) sitting underneath this week’s new snow. This interface (about 30-60cm deep) will be sensitive to human triggering, and periods of additional snowfall will only exacerbate the situation. Be extra careful right now. We have had a slow build-up of stress in the upper snowpack and it will be waiting to be released.
Clear, calm weather over New Year’s created widespread surface hoar and weak surface facets. Since then, around 3″ of precipitation (36″ of new snow) has fallen over the region with strong south winds at times. Looking forward: After a break Saturday morning, a strong storm is on tap for Saturday night-Sunday. 12-20 inches of new snow is likely, with freezing levels close to sea level.
( *star means meteorological estimate )
Practice like you play. Dust off your gear and make sure it is fully functional. Put new batteries in your beacons! Make sure everyone in the group has a functioning beacon, shovel and probe – and knows how to use them, keep your skills fresh. If you head into the hills, watch out for avalanche conditions, and be especially careful of rocks and hidden hazards like crevasses beneath the snow. WEAR A HELMET!
Education Video Links:
Click the + Full Forecast link below for each zone to read more. Submit observations. Win prizes. Each snow, weather & avalanche observation will be entered in a raffle drawing. The more observations, the more chances to win!
Forgot your password?
Lost your password? Please enter your email address. You will receive mail with link to set new password.
Back to login
Enter the destination URL
Or link to existing content