Avalanche Forecast

Fair

A ridge of high pressure will keep things dry for Wednesday and Thursday. A temperature inversion should keep the valleys cooler and under fog but above the fog should be mostly sunny. Alpine winds should remain light on Wednesday and Thursday morning but will progressively increase on Thursday afternoon. The next frontal system should reach the interior on Thursday night but is only expected to yield 10-15cm. By Friday afternoon the system should be finished and some sun is expected. Alpine winds should be moderate-to-strong from the SW during the weak frontal system.

On Monday, isolated natural activity was reported in Rogers Pass. On Sunday, several natural size 3 glide slabs were reported around Nakusp. These released on the ground with average depths of 2.5m. These were east aspect between 1200 and 2000m elevation. Also reported was a size 2 which was remotely triggered by a helicopter from 100m away. This occurred on a west aspect at 2200m and released down 1m on the mid-Dec layer. Finally, a snowcat intentionally started a size 2 avalanche by pushing snow over the edge of a ridge. This also released on the mid-Dec layer down 60-100cm and occurred on a NE aspect at 1900m. Natural activity is not expected on Wednesday but remains possible, specifically on sun exposed slopes. Human-triggered persistent slabs remain the main concern for the foreseeable future.

A breakable melt-freeze crust exists below around 1500-2000m on all aspects and on steep sun-exposed slopes at all elevations. A layer of surface hoar as big as 20mm sits on top of this crust on all aspects up to ridgetop. Recent warm temperatures have aided in the settlement of the week old storm snow. Down 80-140cm is the touchy mid-December surface hoar/crust layer which remains sensitive to human triggering. This persistent weak layer remains reactive in snowpack tests and continues to produce large, destructive avalanches. The layer appears to be the most reactive at treeline or just below treeline.