As of Wednesday, March 14
The past week has brought us a typical smorgasbord of spring conditions ranging from daily melt-freeze cycles to cool spring time convective showers. Most recently a storm passed through the ski hills on Monday giving strong south and westerly winds and 14 cm of storm snow down to 800 metres. As of this morning the soft slabs laid down by this storm were still reactive to ski and explosive testing, producing avalanches in the size 1 to 2 range.
No deeper releases have been observed so far involving the faceted weakness in the snowpack base.
Prior to the Monday storm snow stability surrounding the ski areas was generally good, except for some periods of warming at lower elevations and on sun-exposed aspects. However, other nearby regions were raising some red flags or even producing avalanches failing on a layer of large surface hoar crystals buried back on the 25th of March. Observers in Garibaldi Park, Brandywine and other areas were seeing up to 60 or 70 cm of soft slab shearing easily on this fragile layer. One group triggered a size 2 slab starting on a 25 degree slope, then promptly triggered another one up slope and 50 metres away. This surface hoar weakness can be found at all elevations on aspects sheltered from direct sun and wind exposure.
Near the ski hills we have seen no avalanche activity involving this layer as it was either destroyed by skier traffic before burial or it lies under a lighter load of 20 to 40 cm of storm snow.
The present cool and stormy conditions will both preserve the weak shear strength and continue to stress the surface hoar crystals with each layer of added new snow. Be very careful in choosing sites for pit observations. You may not find the buried surface hoar at your pit site due to wind or sun effect. Meanwhile 100 metres down your chosen line you may encounter (hopefully not too surprisingly) a carefully nurtured garden of surface hoar feathers delicately supporting half a metre of slab.
As noted above the forecast calls for a series of weak fronts embedded in a cool westerly flow, producing periods of new snow and wind loading. The breaks in between are sure to produce some periods of intense sun warming on solar aspects. Expect rapid changes in snow stability with the above noted weather trends and stay alert for the potential for deeper slab weaknesses at all times.
Currently the avalanche danger scale is rated as MODERATE, with occasional trends to CONSIDERABLE. Call 938-7676 for local daily backcountry advisories, or the Canadian Avalanche Centre (1-800-667-1105 or avalanche.ca) for province-wide advisories.
