Avalanche Forecast
Issued: Dec 28th, 2011 9:39AM
The alpine rating is Wind Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Friday
Weather Forecast
Overnight Wednesday: Snow amounts 10cms. Moderate ridgetop winds from the SW. Thursday: A ridge of high pressure will likely build. This will bring dryer conditions, with possible sunny breaks in the Purcells. Ridgetop winds from the SW 30-70km/hr. Freezing levels around 1000m. Friday: Expect another frontal system spreading light-moderate amounts of snow. Winds will pick up from the South. Saturday: Mainly dry conditions.
Avalanche Summary
Numerous small size 1 slab and loose avalanches occurred on Tuesday. As more snow and wind enters the region its likely that we'll start to see more avalanche activity on these weak layers.
Snowpack Summary
Consistent winds have deposited soft slabs onto leeward exposed slopes, and terrain features. Up to 30cms of snow has buried a new surface hoar layer (December 24th). I'm not sure how widespread this exists in the Purcells, but it also formed in adjacent regions which makes me suspicious. With additional load this layer may fail stepping down to the mid-December layer. There is about 50cms of snow sitting over the Mid-December interface of surface hoar and facets. Some observations suggest this layer is gaining strength, but still remains within the threshold of human triggering where there are sufficient load/slab properties. This will be the layer to watch as more snow and wind accumulates this week. Below this weak interface the mid pack is well-consolidated and strong. Near the base of the snowpack there are a few layers that have the potential to trigger with very heavy loads or from shallow spots. These include a surface hoar/crust/facet layer from early November, and the basal facets/depth hoar that are currently unreactive but still a concern in areas that have not previously avalanched.
Problems
Wind Slabs
Aspects: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 29th, 2011 8:00AM