Avalanche Forecast

SATURDAY NIGHT: Clear with increasing clouds, trace of new snow, light to moderate west wind, alpine temperature -4 C, freezing level 600 m. 

SUNDAY: Cloudy in the morning and clear in the afternoon, trace of new snow, light to moderate southwest wind, alpine temperature 0 C, freezing level rising to 2000 m.

MONDAY: Cloudy with snowfall, 5 to 10 cm new snow, moderate to strong west wind, alpine temperature -4 C, freezing level 1500 m.

TUESDAY: Cloudy, up to 3 cm new snow, light to moderate southwest wind, alpine temperature -5 C, freezing level 1300 m. 

Observations on Friday were limited due to visibility. A natural avalanche cycle of small slabs up to size 1.5 was observed, as well as a few large (size 2.5 to 3) storm slab avalanches on northeast and south aspects at treeline. Skiers triggered small storm/wind slab avalanches, and explosives triggered numerous large (up to size 2.5) avalanches. 

A handful more storm and wind slabs were triggered by riders on Thursday to add to the many avalanches observed in the previous few days. Most of the storm slabs released on the surface hoar layer described in the Snowpack Summary, often occurring between around 1700 and 2200 m on east, north, and west aspects. Check out some good example photos here. 

Large avalanches are still expected to be easily triggered by riders on Sunday in areas where the buried surface hoar described in the Snowpack Summary exists. Avoidance of avalanche terrain, particularly where the surface hoar may exist, is your best bet for having a safe day.

The recent storm brought 20 to 40 cm with locally higher amounts. The snow has formed new storm slabs in areas sheltered from the wind and wind slabs in exposed terrain at higher elevations from strong south to southwest wind. 

The snow loaded a weak layer of surface hoar crystals 5 to 15 mm in size. Forecast warming may also increase the likelihood of triggering a slab. The layer may be around 60 to 100 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 120 to 250 cm. The last reported avalanche was on January 31 from a large explosive, and before that on January 23. 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.

• Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
• Shooting cracks, whumphs and recent avalanches are strong indicators of an unstable snowpack.
• Avoid steep slopes when air temperatures are warm, or solar radiation is strong.