Extra caution!There have been two large skier-triggered slab avalanches near Kimberley and one near Golden in the last week.
Weather Forecast
A dominant ridge of high pressure brings light northerly winds, sun and increasingly mild temperatures in the alpine. Below about 1700 m, expect valley cloud, flurries and cold temperatures. Alpine temperatures are expected to reach 0 degrees by Friday afternoon and climb above 0 through the weekend. For more details check out https://avalanche.ca/weather.
Avalanche Summary
On Thursday, a skier triggered a size 2.5 slab on a NW aspect at about 2500 m near Golden. It is thought to have failed on the early Dec persistent weak layer, down 30-60 cm. There has also been activity clustered in a region to the west of Kimberley. On Tuesday, a skier triggered a size 2 persistent slab. Last Sunday, a skier triggered a size 3 slab. Skiers also remotely triggered a size 2 slab the week before. These all failed on the early December surface hoar layer and were on all aspects between 1600 m and 2100 m. Small loose dry avalanches and cornice falls have also been reported.
Snowpack Summary
Conditions are variable across the Purcells. In the south (west of Kimberley), a prominent layer of large buried surface hoar is reactive to human triggers. In this part of the region, it is buried down 40 cm with a cohesive slab above it. Further north, it is 60-120 cm down and has been sporadically reactive to skiers on NW facing alpine slopes near Golden. At alpine elevations, this interface exists as a surface hoar/ facet layer sitting on a crust. The lower snowpack is generally considered to be well settled.New and old wind slabs may be found in the lee of ridges and ribs on a variety of slopes.
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.
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.
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.