Avalanche Forecast

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. 20-30cm of snowfall is possible but freezing levels are forecast to climb as high as 1800m during the day. Snowfall amounts are expected to be the highest at the south 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.

Observations have been very limited during the storm. On Friday, a natural size 3.5 was reported from a steep NE aspect at 2100m. This was a wind loaded start zone and the slab was 60cm thick. Ski cutting also produced a size 1 storm slab with a 50cm thick slab. On Saturday, several natural size 1 avalanches were reported from below treeline elevation. On Sunday, a ski cut produced a size 1 on a NE aspect at 2000m with a 30cm thick storm slab. In the Northern Monashees, an avalanche was remotely 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 remains a serious concern, especially below 1800m where the surface hoar layer is most reactive. Widespread 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 60-90cm 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.