Avalanche Forecast

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Sunday night: Clear, moderate southwest wind, treeline low around -10 °C. 

Monday: Sunny in the morning then increasing cloud cover with flurries, moderate southwest wind, treeline high around -3 °C. 

Tuesday: Cloudy, up to 10 cm new snow, strong southwest wind gusting to extreme, treeline high around -2 °C. 

Wednesday: Cloudy, 20-30 cm new snow, strong southwest wind gusting to extreme, treeline high around 0 °C. 

On Saturday, numerous storm slabs up to size 2.5 were triggered by explosives. 

A natural avalanche cycle to size 2 occurred overnight Thu-Fri with accumulating snowfall and wind. On Friday morning, explosives easily triggered storm slabs to size 2.5. Several natural slab avalanches of size 2 and one size 3 released naturally. 

There has been an alarming pattern of large, persistent slab avalanches being consistently reported over the past two weeks. Almost all of these avalanches ran on the early December weak layer. Deeply buried persistent problems like these don't go away overnight, and it remains a serious concern. 

• On Saturday, a large (size 2.5) persistent slab avalanche was triggered by explosives on the early December layer that was reloaded with new snow.
• On Friday, a natural persistent slab avalanche of size 3 released 1-2 m deep on the early December layer at 2100 m on an E aspect in the north of the region. A size 2 persistent slab avalanche occurred naturally and failed on the same layer 30 cm deep. The feature had slid previously, and new snow reloaded the persistent weak layer.
• On Tuesday, explosive control work near Rossland produced a size 2.5 persistent slab avalanche on a layer of surface hoar from late December. 
• On Monday in the neighboring South Columbia region, a natural size 2.5 persistent slab avalanche was reported on a NE aspect at 2200 m failing 80 cm deep on the early December layer.
• A few notables from last week feature in our latest blog Photos of recent persistent slab avalanches in the southern interior. 

15-30 cm of recent storm snow fell with southwesterly wind and warming temperatures, resulting in a denser slab forming over lower density snow. An accumulated total of 60-80 cm of new and recent snow now sits over variable and potentially weak snow surfaces including widespread facets, wind affected snow, and/or surface hoar up to 5 mm in sheltered areas.

The early December crust/facet layer has been responsible for sporadic but very large persistent slab avalanches over the past two weeks. The crust is now buried 120-200 cm deep except in thin, wind affected areas near ridgetops where nearly all of the recent avalanches have been triggered. We have uncertainty around whether new snow loads will cause this layer to fail naturally in the short term, or to help it heal in the longer term.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Be aware of the potential for large avalanches due to the presence of a persistent slab.
• Avoid shallow, rocky areas where the snowpack transitions from thick to thin.