Avalanche Forecast
Issued: Dec 28th, 2011 8:35AM
The alpine rating is Wind Slabs, Storm Slabs and Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Poor - Timing of incoming weather is uncertain
Weather Forecast
Wednesday night and Thursday: Another system arrives bringing 15-20cm of snow, tapering off on Thursday afternoon. The freezing level drops from 1000m to valley bottom overnight. Winds are strong from the SW. Friday and Saturday: Mainly cloudy with light snowfall on Friday (around 5cm) and possible sunny breaks on Saturday. Freezing level at valley bottom. Winds are light to moderate from the SW.
Avalanche Summary
Observations from the Microwave area (S. of Dennis Lake) on Dec. 26: Several easily triggered soft slabs on steep features up to treeline. No alpine observations due to cranking winds and blowing snow. I would expect some natural avalanche activity at higher elevations, primarily in wind loaded terrain.
Snowpack Summary
Strong winds have been the biggest story recently. Exposed windward slopes have been scoured and wind slabs have formed in lee terrain and may be susceptible to human triggering. There is now around 55-70cms of snow sitting on a surface hoar/crust/facet combo which is the result of the early December dry spell. This crust is widespread and exists in most start zones up to 2000m. Facets can reportedly be found above or below the crust. Prior to being buried, the surface hoar was destroyed by high winds in the alpine, but still coexists with the crust at treeline and below. What is the tipping point of this weak interface? In areas where this interface has reached its threshold, natural and human triggered avalanches up to size 2.5 have occurred. If they have yet to happen, I suspect they are gaining some strength but would still react to a rider trigger, especially in steeper, unsupported terrain features. In short, the upper snowpack is variable and deserves caution. It will also see increased load with forecast wind and snow. Beneath this the midpack is well settled and strong.
Problems
Wind Slabs
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Storm Slabs
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 29th, 2011 8:00AM