Avalanche Forecast

Several large persistent slab avalanches were triggered by explosives on Monday, releasing on the weak layers described in the Snowpack Summary. They all occurred between 2100 and 2200 m, on all aspects, and were mostly between 80 and 150 cm deep. The results show us that these layers are still a concern and, if triggered, could produce large, high consequence avalanches.

New snow falls over a surface crust on south aspects and elevations below treeline. Elsewhere, it blankets 30 to 40 cm of previous snow overlying a hard melt-freeze crust that extends up to 2000 m. Where it is robust enough to do so, this crust appears to be effectively bridging deeper instabilities, making them more difficult to trigger.

The two prominent layers of concern are a 60 to 80 cm deep surface hoar/crust layer that was buried in mid-December and an 80 to 150 cm deep surface hoar/facet layer buried in mid-November.

Wednesday night

Mostly clear, southeasterly wind increasing to 30 km/h, treeline temperature around -10 °C.

Thursday

Cloudy with up to 5 cm new snow, 30 km/h southeast wind, treeline temperature around -4 °C.

Cloudy with 5-15 cm new snow, 30-40 km/h southeast wind, treeline temperature around -2 °C, freezing level 800 m.

Cloudy, up to 5 cm new snow, southeast wind easing to 15-20 km/h, treeline temperature -1 °C, freezing level 800 m.

More details can be found in the Mountain Weather Forecast.

• Pay attention to the wind, once it starts to blow fresh sensitive wind slabs are likely to form.
• Be mindful that deep instabilities are still present and have produced recent large avalanches.
• Use conservative route selection and resist venturing out into complex terrain.
• Remote triggering is a concern, avoid terrain where triggering slopes from below is possible