In the terrain adjacent to the Whistler-Blackcomb ski areas the avalanche danger is rated as MODERATE in the alpine and LOW at treeline and below.
The best conditions this week have been found in the alpine terrain where, in spots, the Dec. 19 crust has been adequately covered by a layer of low density snow. As well, the inverted temperatures at the higher elevations have provided a welcome respite from the valley icebox.
Early in the week moderate to strong NE winds formed some isolated windslabs on lee pockets of terrain that were close to the ridgelines. Initially these slabs were very reactive to the weight of a person, but they seem to have tightened in and become less sensitive with time. The most recent crust is still very much in evidence on ridge tops and windward slopes, but is covered by about 50 cm of storm snow in less wind-affected terrain. Thanks to a steep temperature gradient in the upper snowpack, this crust and the overlying storm snow are going through the faceting process. You may notice that the once-strong crust will no longer support a footstep, and the sugar like quality of the storm snow is becoming more evident each day.
Surface hoar can be found at all elevations, but it is much more developed at treeline and below treeline. The snowpack in any shallow, rocky terrain has continued to rot and will bear close watching when the overlying slab begins to build. All in all, lots of potential weaknesses that may haunt us in the future.
The long-range models don’t seem to be sending any big dumps of snow our way. Periods of flurries accompanied by some warming are expected for the end of the week, but the arctic air should re-establish itself again early next week.
From the Duffey Lake Area (courtesy of M.O.T.): The snowpack remains very shallow and facetted with weeds and rocks protruding through several crusts and into many ski lines. The crust is breaking down under 10-15 cm of loose facets and will no longer support the weight of a person on foot but will still support a skier or boarder.
Snowpack depth at the pass is 60 cm; Cayoosh Canyon has less than 20 cm and in the high Alpine the snowpack varies from 80 to 120 cm. Very isolated 4F soft slabs appear limited to near wind-exposed ridge-top sites. These slabs can be skier triggered on the steepest rolls but with little mass or tendency to propagate, which is good since an underlying crust could create long run out distances. Surface hoar has grown up to 8 mm at treeline and below but has disappeared in any areas that are exposed to wind and sun effect. The surface hoar and facetted grains will persist for a stability forecasting challenge under future slabs if it ever snows.
As always, conditions may change and do vary. Call 604-938-7676 for daily avalanche bulletins or peruse the CAA website at avalanche.ca.
