Regions
Northwest Coastal.
The chances of triggering a slide may have decreased, but the consequences if triggered could be disastrous. Conservative terrain selection remains critical.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Sunday: Cloudy with a chance of flurries and sunny breaks late in the day. The freezing level is near 600-800 m. Winds are generally light. Monday: A mix of sun and cloud with a chance of flurries. The freezing level is near 400 m and ridge winds are light or moderate from the NW. Tuesday: A mix of sun and cloud with a chance of flurries. The freezing level is near 400 m and ridge winds are light or moderate from the NW.
Avalanche Summary
There were no new reports of avalanches on Friday; however, there is more evidence of a fairly widespread natural cycle earlier in the week. Many observers reported slabs up to size 3, mainly from steep open features at and below treeline. Observations are generally limited in the alpine but a couple observers noted a surprising lack of slab activity at higher elevations. Cooler and drier conditions should help stabilize the snowpack and reduce the likelihood of triggering. That being said, there is still potential for triggering lingering persistent weaknesses and producing very large and destructive avalanches.
Snowpack Summary
Generally 15-25 cm of lower density new snow overlies moist or wet snow, or previously wind affected surfaces in the alpine. Fresh wind slabs are likely in lee and cross-loaded features in the alpine and at treeline. The January 9th surface hoar/facet layer is down 70-150 cm in most places, and remains a concern on all aspects and elevations. Around the same depth you may also find a surface hoar/facet interface from around New Years. In the wake of the recent storm, there is a lot of uncertainty regarding the reactivity and distribution of this destructive persistent avalanche problem. Additionally, the snowpack will require time to adjust to the stress of heavy storm loading. A very conservative approach to mountain travel is still required.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.