Storm slabs may continue to be reactive to human triggers, and deep persistent weak layers continue to be a concern.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Tonight: Overcast with a chance of flurries combined with moderate westerly winds and freezing at valley bottoms. Wednesday: Mix of sun and cloud with moderate southwest winds and daytime freezing levels at 1200 metres. Thursday: Temperatures trending colder as the arctic air descends, combined with light southeast winds and 3-5 cm of new snow. Friday: A few more cm of new snow, light winds, and alpine temperatures near -20.
Avalanche Summary
A natural cycle during the storm up to size 1.5 was reported on Tuesday from the Limestone area. Cornice growth was reported to be significant and may have triggered at least one of the storm slabs. Also keep in mind that the deep persistent slab problem is a low probability/high consequence scenario that warrants extra caution around large open slopes, especially in shallow snowpack areas. There was a report today of a size 3.5 avalanche at Mt Harmer in the Lizard/Flathead region that released on or stepped down to the deep weak layer near the ground.
Snowpack Summary
On Limestone ridge today there was 15 cm of new storm snow at 2100 metres elevation. The height of snow on the ground was 160 cm and the foot penetration was 20 cm. The December facets were down 70 cm at this location and produced hard sudden collapse compression test scores in snow profile tests. This elevation is above the extent of the recent rain crust that extends up to about 1900 metres. A deeply buried weak layer of facets (sugary snow) continues to be a concern in most areas of the region. If triggered this deep weak layer may result in very large avalanches down to near the ground.
triley,
Avalanche Canada
