Avalanche danger will be driven mostly by the wind, as snow amounts gradually accumulate this week.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
Monday Night: Only trace amounts of new snow expected overnight.Tuesday: 5-10 cm new snow expected with moderate southwesterly winds. Freezing level rising to around 600 m at the end of the day.Wednesday: Flurries. Moderate northwesterly winds. Freezing level around 1200 m.Thursday: Light snow, 2-4 cm. Strong southwesterly winds. Freezing level rising to around 1400 m.
Avalanche Summary
Several size 1.5 natural wind slab avalanches were reported from a steep south through southwest facing alpine feature on Friday.
Snowpack Summary
Light amount of new snow and recent winds have created wind slabs in the alpine and isolated treeline areas. Incoming new snow will likely not bond well on account of the faceted (sugary) nature of the upper snowpack.There are two layers of surface hoar (weak feathery crystals) being reported in the top 15-30cm. The surface hoar is most prominent at treeline, but it may be found in sheltered alpine areas. Both of these layers may be associated with a sun crust on south aspects in some areas.Another major feature in the snowpack is a combination of a crust and faceted (sugary) snow found at or near the base of the snowpack. This layer is most prominent in the alpine.The early season snowpack is highly variable in the Purcells. Total snowpack depths vary greatly throughout the region with anywhere between 70 and 150 cm in the alpine tapering rapidly at treeline and below. In shallow snowpack areas, the bottom half of the snowpack is reportedly weak and "hollow" feeling on shady aspects due to sugary, faceted snow.
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.