Weak December layer begs caution

 | January 3, 2012

With the deep La Nina winter of 2010-11 fresh in skiers’ minds there’s talk of another round with the coveted queen this winter as powder skiing was off to an early start in the Monashees. Early season keeners were out skinning and skiing fresh lines as early as the end of October. By the end of November some areas north of the Trans Canada Highway were reporting up to two metres of snow at treeline and 1.5 m in southern regions.

La Nina cool weather continued into early December but switched her gears to unseasonably dry with no significant snowfall until Dec. 14. This two week dry spell formed a weak layer of sun crust on slopes steeper than 30 degrees, and facets and surface hoar on all other slopes. Initial storm loading and warming on Dec. 17 produced a widespread natural cycle of avalanches up to size 2.5—large enough to bury or injure a skier. In fact, a skier was recently caught in a lower slope valley avalanche in Roger’s Pass. Currently a slab up to 50 centimetres overlies this weak layer which can be triggered by skiers in specific terrain features such as planar open unsupported features.

With lingering instability in the snowpack it’s the perfect time to take an avalanche course. The Canadian Avalanche Centre has many to offer, and has also introduced a new one day Companion Rescue course, another great way to hone your rescue skills from experienced professionals. Remember, an effective avalanche rescue needs to happen in five minutes or less. That’s a great way to improve your rescue skills. With heavy snowfall in the forecast, it looks like powder skiers will be given a welcome gift of the fluffy stuff to coat Monashee ski resorts and backcountry slopes. However, with this additional storm load be very cautious of another possible avalanche cycle on the buried Dec. 14 weak layer.

Check the Public Avalanche Bulletin for updated conditions and advice for travelling in avalanche terrain. Snowpack and avalanche information is also available on the Association of Canadian Mountain Guides (ACMG) Mountain Conditions Report and Powdercloud.