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Backcountry Avalanche Advisory


As of Wednesday, Jan. 21
Alpine: Considerable (trending to moderate by Friday)
Treeline: Moderate
Below Treeline: Moderate (trending to low Thursday, Friday)
Travel Advisory: The amazingly warm temperatures are finally starting to affect the surface layers. The upper snowpack has been warming and strengthening, but the underlying facet weakness remains relatively unchanged. Numerous large slab avalanches have been observed over the past week. Expect natural and skier-triggered avalanche activity on solar aspects with the potential for very large results. The avalanche danger will increase through the day with solar warming.
Avalanche Activity: The natural activity from last week has tapered off as the upper snowpack has begun to stabilize. Explosive testing conducted during the past several days has produced some deep slab avalanches in isolated areas only. They have been failing in the facets above the Dec. 6th crust. The unseasonably high freezing levels and solar radiation have produced wet loose slides and cornice failures up to size 2 on solar aspects.
Snowpack: The current snowpack is very atypical for the West Coast. The shallow early December snowpack was exposed to prolonged cold temperatures which caused it to become weak and faceted. Depth hoar formed in shallow rocky terrain. Compounding this problem is the underlying Dec. 6 raincrust that provides a nice hard sliding surface. The crust/facet combo is now buried up to 200 cm below the surface on some lee slopes. Stability tests have recently indicated that these layers are beginning to strengthen. Not all start zones have run on this crust and we may begin to see renewed activity within these layers with rapid changes in weather or with increased loading above them. Shallow rocky terrain is very rotten and will be prone to deeper releases in the future. Below treeline terrain is quite variable depending on aspect and elevation. Some areas have been crusted over while others have a layer of surface hoar sitting on winter-like snow.
Weather: Continued sunny and mild conditions will persist for today. We should see increasing cloud as this ridge of high pressure begins to break down and a weak system arrives onshore. Modified arctic air is expected to move down the coast bringing mainly dry and cold conditions over the weekend.
- Whistler Snow Safety

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