Avalanche Forecast

Fair - Due to limited field observations

A substantial upper ridge over the interior will bring dry, conditions under a cool northwesterly flow. Ridgetop winds on Thursday will be 30-40km/h from the northwest. Alpine temperatures will sit at -6 degrees, with the freezing level rising to 900m then dropping back to valley bottom at night. Friday through the weekend we can expect similar conditions with moments of convective power flurries and strong ridgetop winds that will die off and clear sunny skies with light winds will remain.

Control work done on Tuesday produced a size 2 avalanche running to ground from a northeast aspect. There is still very limited observations from the region, so you will have to do the detective work. I suspect these conditions will continue through the forecast period, and it's likely that avalanches are susceptible to human/ sled triggering. With clear skies ahead this is a good opportunity to make snowpack, and avalanche observations from your surrounding mountains before jumping in to deep.

Snow depths are quite variable through the region. In the alpine there is 170- 250cm. At treeline there is anywhere from 130-150cm. I suspect Sunday's warm, moist storm combined with strong southwesterly winds created stiff wind slabs on lee slopes, and storm slab instabilities. Changing winds at ridgetop and treeline may redistribute some of our previous storm snow, forming new wind slabs on southerly aspects. A highlighted concern for the Purcells was the mid-November storms that created a heavy slab over a weak basal faceted base. The Purcells saw a significant cycle of large avalanches running full depth as a result. (The Lizard Range also saw very similar results all failing on the weak basal layers.) With this clearing trend upon us I bet you'll be able to see evidence of older, large avalanches that occurred on your local mountains. I do suspect that these slopes will be ripe for human, and/or sled triggering especially on northerly aspects where avalanche activity has not occurred. Remember these avalanches are failing on weak facetted (sugary) snow at the bottom of the snowpack, producing full depth avalanches. The upper snowpack seems to be tightening up, forming a stronger mid-pack but if an avalanche is triggered in the upper layers or initiated from a shallower spot in the snowpack it could step down to weak basal facets at the ground creating large and avalanches with very high consequences.