Wind slabs continue to be a concern for human triggering, and the persistent weak layer has been active in isolated locations during the past week.
Summary
Confidence
Moderate - Due to the number of field observations
Weather Forecast
Light winds and -10 in the alpine overnight as the freezing level drops to valley bottoms. Broken skies or scattered cloud on Monday with alpine temperatures around -10. Mostly sunny with light winds on Tuesday. Cloud, wind, and temperatures increasing during the day on Wednesday ahead of the next Pacific system moving in from the coast.
Avalanche Summary
No new avalanche observations over the weekend from this region. On Friday, our field team reported several natural avalanches up to size 3.0 on east aspects that were visible from Crown mountain in the Elk Valley North area. These avalanches probably started from wind loading or cornice falls. The interesting observation about these slides was that they stepped down in the track or at the fans around 1900 metres elevation and resulted in a larger avalanche than the initial release. This suggests that it is possible to trigger an avalanche in the run-out with the right load in the wrong place.
Snowpack Summary
I suspect that a supportive melt-freeze crust has developed below about 1600 metres due to the cooling trend and lower freezing levels. Recent strong to extreme winds developed storm slabs in the alpine and at treeline, and also resulted in new fragile cornice growth. The persistent weak layer of buried surface hoar was found down 45 cm at 1850 metres and down 90 cm at 2150 metres in the Crown mountain area, and compression tests gave hard sudden planar results. A weak crust/facet layer from early-December is typically down over 1m. It has become difficult to trigger this layer but it is still reactive in snowpack tests suggesting that if you are able to trigger it, the layer is capable of wide propagations and large destructive avalanches.
triley,
Avalanche Canada
