Avalanche Forecast

WEDNESDAY NIGHT: Cloudy with clear periods, trace of new snow, light to moderate west wind, alpine temperature 0 C, freezing level 2200 m. 

THURSDAY: Mix of sun and cloud, trace of new snow, light to moderate northwest wind, alpine temperature +3 C, freezing level slowly dropping to 1800 m.

FRIDAY: Sunny, trace of new snow, moderate northwest wind, alpine temperature -6 C, freezing level 1400 m. 

SATURDAY: Sunny, light northwest wind, alpine temperature -1 C, freezing level 1500 m. 

On Tuesday, skiers triggered several small slabs on the buried weak layer. One was triggered from a distance away. Just south of the region explosives triggered very large slab avalanches up to size 3 on the buried weak layer.

On Monday, skiers triggered several slab avalanches on the buried weak layer and avalanches also released naturally on this layer reaching up to size 2.5. The avalanches were 40-60 cm deep. Several cornice failures were reported and some triggered wind slabs on the slopes below. A deep persistent slab avalanche of size 2.5 was triggered by a machine and released on the early December facet/crust layer described in the Snowpack Summary.

On Sunday, skiers triggered large avalanches that released on the buried weak layer with surface hoar crystals. Check out some good example photos here. Some avalanches on this layer were triggered remotely. Several large and one very large (size 3.5) avalanche released naturally on the buried weak layer. The avalanches released at all elevation bands and all aspects. Explosives triggered numerous storm slabs up to size 2 below treeline on southeast aspects. Many large wet loose released naturally on sun-exposed slopes. Several large wind slab avalanches released naturally in the alpine and at treeline on east, south and west aspects.

The recent storm brought 10 to 30 cm snow. The snow has formed wind slabs with strong south to southwest wind in exposed terrain in the alpine and at treeline. A sun crust formed on sun-exposed slopes at all elevations.

The snow loaded a weak layer of surface hoar crystals 5 to 15 mm in size. The layer may be around 40 to 80 cm deep, which is a prime depth for human triggering. The layer is most prominent in areas sheltered from the wind. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. The layer may not exist on steep sun-exposed slopes, where a melt-freeze crust may be found instead.

The facet/crust layer that formed in early December is buried around 100 to 240 cm. The last reported avalanche was on February 7 in the southwest of the region. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche could step down to this layer. Humans are unlikely to trigger it, with perhaps the exception in thin, shallow snowpack areas. Check out the forecaster blog for more information.

• Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
• Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
• Be aware of the potential for large avalanches due to the presence of buried surface hoar.
• Uncertainty is best managed through conservative terrain choices at this time.