Watch for areas that have recently been affected by the wind. Wind slabs are expected to be lingering in leeward terrain features. Buried weak layers remain an isolated concern and avalanches have the potential to step down to a deeper layer.
Confidence
Moderate - Wind speed and direction is uncertain
Weather Forecast
Sunny conditions are expected on Wednesday with treeline temperatures around -15C in the afternoon and light northerly wind in the alpine. Sunny conditions continue for Thursday and Friday with treeline temperatures remaining around -15C during the afternoon and light to moderate alpine wind from the northwest.
Avalanche Summary
On Monday, ski cutting produced numerous size 1-1.5 storm slabs. These slabs were typically 15-20 cm thick and were reactive in the alpine and at treeline. One natural was also observed from a steep, unskiable terrain feature. On Wednesday, recently formed wind slabs may still be reactive to human triggering. With the winds recently switching directions, wind slabs should be expected on a variety of aspects. Persistent slab avalanches also remain an ongoing concern. Buried weak layers are creating a low probably, high consequence problem for the region. Extra caution is recommended in shallow snowpack areas of the region.
Snowpack Summary
15-20 cm of new snow has buried a variable old snow surface which consists of heavily wind scoured surfaces or old wind slabs in exposed terrain, surface hoar in sheltered terrain, and/or widespread faceted old snow. Recent moderate winds from a variety of directions is expected to have redistributed some of this new snow in wind exposed terrain. The mid pack appears to be variable throughout the region and the structure is dependant on snow depth. In deeper snowpack areas, the snowpack appears to be well settled and right side up with isolated concerns for the mid-December weak layer. In shallow snowpack areas and lower elevations, the snowpack is heavily faceted and there are concerns for the mid-December weak facet layer as well as old faceted crusts deeper in the snowpack and a weakness at the bottom of the snowpack. Due to inconsistencies in snowpack structure throughout the region, the snowpack needs to be treated with respect and further investigated at a local scale in your riding area.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
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.