A weak layer of surface hoar that is now buried around a metre deep is creating a low likelihood, high consequence scenario. Continue to investigate this layer carefully.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Tuesday: Sunny / Moderate to strong northeasterly winds / Average temperature at treeline -13 C.Wednesday: Sunny / Moderate to strong northeasterly winds / Average temperature at treeline -12 C.Thursday: Sunny / Moderate to strong northeasterly winds / Average temperature at treeline -16 C.
Avalanche Summary
On Sunday, there was a report of a size 2 natural avalanche west of Terrace. It was on a southwest aspect and it was estimated that it failed on the mid-November surface hoar layer around a metre deep. This layer may remain reactive to human triggers in isolated locations for weeks and requires continued investigation.
Snowpack Summary
Clear skies and strong outflow winds have created a variety of snow surfaces including scouring and hard wind slabs in exposed areas and up to 12 mm surface hoar formation in sheltered areas. Strong easterly winds over the past week have created wind slabs on aspects you may not expect them. Wind slabs could be present on all aspects in open areas at treeline and above. A layer of surface hoar which was buried mid-November is down 60-120 cm in many parts of the region. This layer may be reactive to human triggers in isolated locations or could be triggered by a smaller wind slab that 'steps-down' to this layer. Treeline snow depths are around 140-200 cm in the Terrace and Stewart areas, but substantially less further north. Concerns in the north are basal weaknesses that may exist in the shallower snowpack areas especially on smooth alpine features like glaciers.
jsmith,
Avalanche Canada
