Avalanche Forecast
Issued: Jan 13th, 2015 8:49AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
rbuhler,
Avalanche Canada
Avalanche activity on the tricky mid-Dec weak layer has decreased recently but this layer should still be treated as a major hazard for the foreseeable future. Large and destructive human-triggered avalanches remain possible.
Summary
Confidence
Fair
Weather Forecast
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.
Avalanche Summary
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.
Snowpack Summary
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.
Problems
Persistent Slabs
The persistent weakness buried mid-Dec is spotty in distribution and widely variable with regard to reactivity which makes management tricky. It remains most prevalent at and just below treeline where human triggered avalanches are most likely.
Use conservative route selection, stick to moderate angled terrain with low consequence.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 14th, 2015 2:00PM
