Enjoy the new snow but stay tuned in to signs of consolidation and wind effect as you travel. New storm slabs will be touchy on Friday.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Friday: Mainly cloudy with sunny periods and no new snow. Winds light to moderate from the west. Alpine temperatures to -12.Saturday: Mainly cloudy with isolated flurries and a possible 5cm of new snow. Winds light from the north. Alpine temperatures to -12.Sunday: A mix of sun and cloud with no new snow. Winds moderate gusting to strong from the north. Alpine temperatures around -17.
Avalanche Summary
No new natural avalanches have been observed in the region but slope cutting on Wednesday in the Valemount area produced a size 1.5 avalanche with a 60cm crown depth. It is likely that limited observations and conservative terrain choices are obscuring some of the avalanche potential in the region. Expect our continued moderate to strong ridgetop winds along with new snow on Thursday to promote ongoing slab development - particularly in wind-exposed areas. In more sheltered areas, watch for signs of storm snow consolidating into a slab as well as loose dry avalanches triggering easily in steep terrain.
Snowpack Summary
About 35cm new snow lies on the surface after this week's series of storms. In higher elevation terrain, moderate to strong winds have promoted slab formation on lee and cross-loaded features. In sheltered areas and lower elevations, the low density snow has only just begun to show signs of consolidation into soft slab. 65-100cm below the surface you'll find the mid-December interface which consists of a variety of old snow surfaces including wind affected snow, faceted (sugary) crystals, and/or surface hoar crystals. Recent tests suggest the the new snow is well bonded to the interface in some areas. However, a few public and professional reports suggest this layer may be reactive in some areas and worth investigating before pushing into steeper terrain. The thick mid-November crust layer typically sits 1-2 m down in the snowpack. This layer is considered dormant at this time but remains an isolated concern that we will likely be tracking through much of the season.
Problems
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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.