As of Tuesday, Dec. 18
Its not often we get the season off to such a spectacular start. The skiing has been fantastic under an endless deluge of new snow. The only down side for backcountry travellers is the uphill wading and the usually fierce storm conditions above treeline.
In the past week our snowpack has grown by about 1.5 metres at treeline. On Sunday much of that fell as rain up to 1500m but the return to cooler conditions has brought us back to top-to-bottom powder at the time of writing this report.
During this time the avalanche hazard has swung wildly up and down as loading and warming alternated with cooling and storm snow settlement. At the storm peaks numerous soft slab avalanches occurred naturally or were triggered by ski and explosives. After each storm the shears noticeably strengthened toward fair stability, but just as things would start looking up we would get slammed again.
Typically the good skiing was all below treeline in low density powder, while the treeline and alpine received layer after layer of stiff, cakey windslab with constant high winds. These widespread windslabs are currently the notable feature of the snowpack.
The forecast calls for a period of grace after Tuesday’s storm as the jet stream slides down to nail California for a while. The storm snow should strengthen steadily in this post-storm period but before we cast all caution to the wind let’s consider a few factors. First and foremost we have received a wopping pile of snow lately and if our above noted expectations should prove wrong there could be some extremely destructive avalanches waiting out there. In all likelihood serious instabilities will linger in the steeper avalanche start zones and in the more wind-affected, shallower snowpack areas where the November crust and facet weakness still lingers. Cornices should be given their due respect as any of these monsters falling on an otherwise stable slope could well trigger some massive slabs.
This period of calm after the storm and before the next is typically the most difficult in terms of decision making. Improving stability lures us deeper in and we often become prematurely confident. Meanwhile there are always areas that will buck the trend and await the unwary. Lots of observation in pits, careful slope tests, weather trends and avalanche occurrences are your most valuable tools in determining where and when you ski.
As of Tuesday morning the Avalanche Danger rating is HIGH at treeline and above, MODERATE below treeline.
For daily Avalanche Advisories for backcountry regions adjacent to Whistler-Backcomb ski areas call 604-938-7676. For a broader ranging advisory for the South coast mountains and other regions consult the Public Avalanche Bulletin at 1-800-667-1105 or www.avalanche.ca.
