Hi All,
We spent the last couple of days (April 5th/6th) ski touring tree line and alpine terrain on southerly aspects near Gimli and Presley peaks in Valhalla provincial park of the Southern Selkirks.
Given the time of year, we were very pleased to find excellent powder skiing on southerly aspects above 1800m with up to 20cm of new light density snow in past two days. This new snow combined with the previous storm snow made for 30cm to 60cm of recent storm snow, consolidating into a stiffening slab, and overlying a 4cm thick pencil resistance crust above the said elevation. On Monday (April 5th), we saw significant wind transport in the alpine with consistent moderate easterly winds loading westerly aspects and cross loading undulating southerly terrain.
For the most part, all of this new snow seemed to be bonding reasonably well to the crust at treeline and below with stability test showed moderate to hard (resistant) shears. In the alpine things are different. Most of the shear results on that layer were in the moderate range with sudden collapse characteristics. Of note at the interface was a thin (1cm thick) softer faceted layer just above the previously mentioned crust.
Today (April 6th), while skiing a lower angled bench on a west aspect in the alpine we started noticing some cracking and whumpfing in the upper snowpack. One of these whumpf remotely triggered a slab avalanche 100m away in nearby steeper terrain. This size 2 avalanche was 30 to 70cm deep (on the crust), about 80m wide and 100m long. Luckily our terrain choice lead us to be safe at that moment but had we been more exposed/closer the steeper terrain things could have been worse.
Up until now this layer had been more of a concern on northerly aspects. Given the significant recent snowfall, wind transport and poor bond with the underlying crust in the alpine, this layer deserve more respect on southerly aspects too. With a weather forecast promising more snow in the next few days this layer will get deeper and could reach critical load, it is bound to become more reactive naturally and to skier traffic. I believe it is time to avoid exposure to any avalanche terrain in the alpine for the next little while. Cool temps and continued precipitation will likely keep fantastic skiing options in the trees.
Be safe and enjoy a great Spring!
Perhaps winter is finally getting here...
David Lussier
IFMGA-ACMG-CAA
www.summitmountainguides.com
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