Changing weather has added complexity to our wind slab problem. Rising freezing levels early this week may coax our persistent slab problem into action.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Sunday: Mainly cloudy with flurries bringing up to 10 cm of new snow. Extreme southwest winds. Freezing level rising to 1000 metres with alpine temperatures of -3.Monday: Mainly cloudy with isolated wet flurries and a trace of new snow. Winds strong to extreme from the southwest. Freezing level rising to 1900 metres with alpine temperatures of +1.Tuesday: Mainly cloudy with isolated wet flurries and a trace of new snow. Winds strong to extreme from the southwest. Freezing level to 2100 metres with alpine temperatures of +3.
Avalanche Summary
No new avalanches have been reported in the past few days. Our most recent avalanche activity was reported last weekend and included a remotely triggered Size 2 avalanche as well as naturally triggered avalanches to Size 2.5. Some of the natural avalanches involved the full depth of the snowpack.For Sunday, expect recently formed wind slabs to be reactive to human triggering. Older hard slabs will be more stubborn, but also capable of much wider propagation. A storm currently impacting the north coast should bring modest new snow accumulations inland along with strong to extreme southwest winds that will promote new wind slab formation in lee areas. A basal weakness continues to drive a low probability/high consequence problem for the region. Very large avalanches remain possible, especially in shallow snowpack areas.
Snowpack Summary
A light snowfall in some parts of the region has given a thin cover to the widespread wind affected surfaces recently reported in exposed terrain. This includes scoured surfaces, sastrugi, and hard wind slabs. The new snow will contribute to wind slab formation in wind exposed areas. In areas sheltered from the wind, new snow has begun to cover faceted surface snow as well as surface hoar. Below around 1400 m elevation, a rain crust can be expected beneath the new snow. Deeper in the snowpack, several buried surface hoar layers can be found between 30-70 cm deep. Recent reports suggest these layers have generally stabilized but isolated weaknesses may still exist, especially where buried surface hoar is still intact. A generally stiff mid pack sits above weak sugary snow near the ground. This basal weakness woke up during the last storm and produced numerous large avalanches which released on the ground. The layer is dormant for the time being but is expected to wake up with warming, heavy loading, or by the weight of a smaller avalanche stepping down.
cgarritty,
Avalanche Canada
