Avalanche Forecast

Highest snowfall amounts are forecast for the north of the region.

Saturday night: Snowfall 5-10 cm, light to moderate SW wind, treeline temperature around -8 °C.

Sunday: Snowfall 10-25 cm, moderate SW wind, treeline high around -5 °C.

Monday: Snowfall 10-25 cm overnight then clearing, light NW wind, treeline high around -10 °C.

Tuesday: Scattered flurries, moderate NW wind, treeline high around -13 °C.

The theme over the past week has been large cornice failures and wind slab avalanches size 2-3 on north to east aspects in the alpine. On Friday, a couple of small (size 1) wind slabs were triggered by skiers.

Deep persistent slab activity on the early December facet/crust layer slowed down during the dry spell. Evidence of an older persistent slab avalanche was reported on Wednesday in the Selkirks, on a west aspect at 2300 m. On Monday, explosive control triggered a deep persistent size 3 avalanche in the Monsahees, with a fracture line 120 cm deep. Between January 20 and 23, numerous very large (size 2.5-4.5) deep persistent slab avalanches occurred on this layer, typically 100-150 cm deep.

15-35 cm of new snow falls over faceting wind affected surfaces in the alpine, a melt-freeze crust on steep solar aspects & low elevations and a widespread layer of large surface hoar crystals, especially prominent in shady, wind sheltered areas at elevations near the top of the previous valley fog layer (1200-1500 m). New snow is expected to adhere poorly at this interface.

There are three prominent layers in the upper snowpack which have been largely dormant during the dry spell but may become reactive with new snow loads. These include a layer of surface hoar down 20-30 cm, a layer of facets and/or surface hoar from early January down around 40-60 cm, and a thick layer of facets from the end of December down close to 1 m.

The primary weak layer that remains a widespread concern across the Columbia Mountains is a deeply buried crust/facet layer that formed in early December. It is typically down 100-180 cm, but as deep as 250 cm in wind-loaded terrain. This layer is likely to plague our snowpack for the remainder of the season and will be a low probability but extremely high consequence result if triggered. Check out our latest forecaster blog on the crust that never dies.

• Storm slab size and sensitivity to triggering will likely increase through the day.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.
• Dial back your terrain choices if you are seeing more than 25cm of new snow.
• Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
• The trees are not a safe haven right now.
• Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.