Cornices often break further back than expected; give them a wide berth when travelling on ridge tops. Wet loose avalanches may occur on sunny slopes in the afternoon.
Observations are limited at this time of year. Let us know what you are seeing by filling out a MIN report!
Cornices may be weak and reactive to human triggers. Give them a wide berth when travelling on ridges. They are a significant hazard alone and may produce large slab avalanches as they fall onto the slope below. Cornice falls are more likely when the weather is sunny, warm, or windy.
SATURDAY NIGHT: Mainly clear. Alpine temperature drops to -5 °C. 10-25 km/h wind from the northwest.
SUNDAY: Cloud cover increases in the afternoon. Alpine temperature rising to -1 °C. Mostly light northwest wind occasionally gusting to 35 km/h.
MONDAY: Cloudy with sunny periods and isolated flurries, 5 cm of accumulation. Alpine temperature rising to 0 °C. 20-50 km/h wind from the southeast.
TUESDAY: Cloudy with snowfall, 10 cm of accumulation. Alpine temperature rising to -1 °C. 10-30 km/h wind from the southeast.
Avalanche activity the last week has primarily been large cornice failures on north and east-facing slopes. For the most part, these have not triggered avalanches on the slopes below. The exception was one very large (size 4) persistent slab avalanche on Monday that was triggered by a massive cornice failure on a northeast aspect in the Selkirks. The triggering of this avalanche was only possible with an extremely large load and is not representative of the general conditions of the region as a whole.
On Friday, Glacier National Park reported a natural wind slab avalanche (size 2) from a south-facing aspect.
At treeline and above up to 20 cm of consolidated, wind-affected snow covers a crust all aspects up to 2200 m and mountain tops on solar aspects. Recent northeast wind has formed wind slabs on lee aspects below ridgetops and left a variety of wind-affected surfaces. Another prominent crust layer is found 30-70 cm deep.
Cornices are very large and exposure to slopes beneath them should be minimized, especially if the weather is sunny, warm, or windy.
