Avalanche Forecast

Friday night: Partly cloudy, moderate SW wind, treeline temperature around -12 °C.

Saturday: Increasing cloud cover, moderate SW wind, treeline high around -5 °C.

Sunday: Snowfall 15-25 cm, moderate SW wind, treeline high around -5 °C.

Monday: Snowfall 5-15 cm overnight then clearing, light NW wind, treeline high around -10 °C.

The theme over the past week has been large cornice failures and cornice-triggered wind slabs size 2-3 on north to east aspects in the alpine. Dry loose avalanches were also observed up to size 1.5.

On Tuesday, a natural size 1.5 persistent slab was reported on an E aspect at 1900 m in the Monashees north of Revelstoke, likely failing on one of the surface hoar or crust layers 30-45 cm deep.

Deep persistent slab activity on the early December facet/crust layer has slowed down during the dry spell. Most recently, two naturals were reported on Monday, size 2.5-3. 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.

The snow surface is highly variable and consists of a crust at lower elevations and on solar slopes extending into the alpine, wind affected surfaces and wind slabs in exposed terrain, and settling powder in sheltered areas on shady aspects. Large feathery surface hoar crystals have been reported growing widespread in sheltered areas, most prominently at elevations near the top of the valley fog layer. This is a layer to watch out for once it gets buried.

There are three prominent layers in the upper snowpack which are mainly dormant now but could still create a problem during the next storm or warming event. The storm on Jan 20 covered a layer of surface hoar which is now down 20-30 cm. A layer of facets and surface hoar from early January is now down around 40-60 cm. A thick layer of facets from the cold drought end of December is now 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.

• Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
• Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
• Conditions may have improved, but be mindful that deep instabilities are still present.