Avalanche Forecast
Issued: Dec 7th, 2011 8:19AM
The alpine rating is Wind Slabs and Deep Persistent Slabs.
, the treeline rating is , and the below treeline rating is Known problems includeSummary
Confidence
Fair - Due to limited field observationsfor the entire period
Weather Forecast
The current weather pattern is expected to hold Thursday and Friday with a temperature inversion bringing above freezing temperatures to alpine elevations. The associated valley cloud is expected to blow out Wednesday afternoon with moderate northerly outflow winds, resulting in sunny skies at all elevations. A week frontal system is expected for Saturday with increasing cloud and a chance of light precipitation and moderate westerly winds.
Avalanche Summary
Avalanche activity has tapered off throughout the week. Although the likelihood of triggering deep persistent slab avalanches is low, the potential consequences are still very high.
Snowpack Summary
Surface hoar is growing, surface snow is faceting, and pockets of weak wind slab may still be lingering on various aspects in the alpine.Warm temperatures and sun-exposure likely resulted in a surface crust on steep south aspects. Last weekends rain crust is down 20-40cm and extends up to treeline elevations. Basal depth hoar with an associated crust is prevalent in thin snowpack areas, and especially problematic where it is overlying summer firn. Above that, and down 1-2m, are two more crusts mixed with facets, depth hoar, and surface hoar. Recent compression tests in a shallow snowpack area produced moderate sudden collapse results on this deep persistent weakness. Time has allowed the overlying snow to gain strength making it less likely to trigger the deeper weaknesses, but if you do hit the sweet spot, such as a shallow area, the resulting avalanche could have very serious consequences.
Problems
Wind Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 8th, 2011 8:00AM