The recent storm produced many large avalanches. Human triggering will remain likely in the upcoming days and warrants a cautious approach to terrain.
Summary
Confidence
High - Due to the number and quality of field observations
Weather Forecast
FRIDAY: Cloudy with gradual clearing, light southwest winds, freezing levels dropping with alpine temperatures around -5 C.SATURDAY: Cloudy, moderate southeast winds, alpine temperatures around -5 C.SUNDAY: Mix of sun and cloud, light southeast winds, alpine temperatures around -5 C.
Avalanche Summary
On Wednesday, widespread natural avalanches were reported throughout the region. These included size 2 storm slabs and size 2-3 persistent slab avalanches releasing on old surface hoar layers. Loose wet avalanches were reported out of steep terrain below 1200 m. Natural avalanche activity will taper off with the dry and cool weather, but human triggering of storm and persistent slabs will remain likely.
Snowpack Summary
40-60 cm of storm snow in the south of the region has been transported by strong southwest winds in the alpine and at treeline over the past few days. The freezing level has been around 1200 m, and below this level the snowpack is moist or wet. As the storm snow settles into a slab, we are concerned that several of the weak surface hoar or facet interfaces that developed during cold and clear weather may become reactive. The January 5th layer is down 50-80 cm, and the December 25th layer is now down close to 100 cm in deeper snowpack areas. These are not typical conditions for this coastal region, and it may take some time to gain confidence about the distribution and likelihood of triggering these deeply buried weak layers. Areas exposed to cornice fall should be avoided due to the possibility of a cornice triggering a deep weak layer. I suggest a conservative approach to terrain while gathering info after the storm.
shorton,
Avalanche Canada
