Purcells

A natural avalanche cycle is expected on Tuesday. Conservative terrain choices will be critical and travel in avalanche terrain is not recommended.

Moderate - Timing, track, or intensity of incoming weather system is uncertain

The series of storm systems continues for the next few days. The next major pulse is expected to arrive early Tuesday morning. 20-40cm of snowfall is possible but freezing levels are forecast to climb as high as 2000m during the day. Snowfall amounts are expected to be greatest in the north and west of the region. Alpine winds are expected to be strong to extreme from the SW. On Wednesday, another storm pulse is expected to bring another 10-20cm of precipitation with freezing levels below 1500m and strong SW winds in the alpine. Thursday is currently forecast to be unsettled with the potential for both light snowfall and sunny breaks.

On Saturday, explosives triggered a size 2.5 deep persistent slab avalanche in the Dogtooth. This was triggered in a steep, rocky, and unsupported terrain feature and released on the crust/facet interface on the ground. Other explosives resulted in thin wind slabs releasing. On Sunday, explosives triggered storm slabs up to size 2 which were typically 20-40 cm thick. In the Selkirks to the west, three remotely triggered avalanches were reported, the furthest being triggered from 150m away. This suggests that the storm slab is gaining cohesion and the propagation potential of the underlying weak layer is increasing. On Tuesday, touchy storms slab will continue to be very sensitive to human-triggering at all elevations. Remote-triggering may also become a concern, especially below 1800m where the surface hoar layer is most reactive. Natural avalanche activity is also expected with the forecast heavy precipitation and rising freezing levels.

The new snowfall continues to add to a storm slab that is typically around 30-60cm thick. This storm slab sits over the early-Dec interface which consists of large surface hoar below 1800m, sun crusts on south-facing slopes, old wind affected surfaces above treeline, and possibly faceted surfaces in some areas. This interface is becoming highly unstable in parts of the region and should be treated with the utmost respect until the new snow has had time to stabilize. Strong SW winds continue to build thick wind slabs in leeward features at alpine and exposed areas at treeline. Deeper in the snowpack, the surface hoar interface from early November have been dormant but still may wake up with heavy loading or smaller avalanches stepping down. On very high northern aspects, a crust/facet interface may be found near the ground.