Avalanche Forecast

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Wednesday night: Cloudy, up to 3 cm new snow, moderate southwest wind, treeline low around -1 °C, freezing level around 2600 m.  

Thursday: Mostly sunny, light to moderate westerly wind, treeline high around +2 °C, freezing level around 2000 m.

Friday: Mix of sun and cloud, trace of new snow, light southwest wind, treeline high around -2 °C, freezing level around 900 m, possible inversion.

Saturday: Cloudy, trace of new snow, moderate southwest wind, treeline high around -1 °C, freezing level around 1000 m.

By the time of writing on Wednesday, explosives had triggered numerous large (size 2-2.5) storm slab avalanches. A large natural size 2.5 slab avalanche was reported in this MIN post. The avalanche was 30 cm deep and on a weak layer consisting of soft sugary snow and feathery surface hoar from early January. A few large (size 2) and many small (up to size 1.5) natural avalanches were observed.

On Tuesday and Monday, several small (up to size 1.5) storm slab avalanches released naturally and were triggered by skiers.

On Sunday, explosives triggered several avalanches of size 2 to 3. A few of these were persistent slab avalanches and released on the early December layer. A large size 2.5 wind slab avalanche 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 Sunday, a few size 2 to 3 persistent slab avalanches were triggered by explosives. One avalanche released at 1900 m and was more than 1 m deep and 150 m wide. 
• 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. 
• A few notables from last week feature in our latest blog Photos of recent persistent slab avalanches in the southern interior. 

10-30 cm new snow fell with warm temperatures and formed a dense slab. This new snow sits on a crust on steep solar aspects and wind affected surfaces in exposed and open areas. In sheltered areas the new snow might sit on a weak layer of feathery surface hoar. An accumulated total of 70-100 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. 

• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• 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.
• Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.