Avalanche Forecast

On Friday, a size 2.5 skier-triggered deep persistent slab occurred in the Birkenhead. This avalanche was remotely triggered, meaning the skier was a distance away from the slab when it occurred (100 m above). It occurred on a wind-loaded slope in the alpine during a period of strong solar radiation. The crown was 150 cm deep.

Looking forward to Monday, riders should be cautious around pockets of stiff wind slab at upper elevations. These slabs may fail easily where they overlie a slick crust and will be in more atypical locations, as northerly winds have created a reverse-loading pattern. Riders should also be aware of the potential for large and surprising deep persistent slab avalanches. These avalanches present a low probability, high consequence problem and are most likely to occur in rocky, shallow, wind-loaded terrain in the alpine or upper treeline.

Please continue to share any observations or photos on the Mountain Information Network.

Northerly winds have affected open areas in the alpine and treeline, souring windward slopes and creating pockets of wind slabs in lee areas. In sheltered areas, 10-20 cm of recent storm snow is facetting with cold temperatures. A surface crust can be found below 1800 m and all elevations steep solar aspects.

In the midpack, a weak layer can be found 50-100 cm deep, as a decomposing crust, or in many places, it's more of a soft and weak section of the snowpack. There is a widespread weak layer of facets and depth hoar at the bottom of the snowpack.

Generally, the snowpack in this region is weak and shallow. Snowpack depths around treeline are highly variable and range between 150 - 230 cm.

Sunday night

Clear. Alpine temperatures drop to a low of -10 °C. Alpine temperature inversion. Light ridge wind from the north. Freezing level at valley bottom.

Monday

A mix of sun and cloud. Alpine temperatures reach a high of -5 °C. Ridge wind light from the north. Freezing level at valley bottom.

Tuesday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -8 °C. Light ridge wind from the southwest. Freezing level at valley bottom.

Wednesday

Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -5 °C. Ridge wind 30 km/h gusting to 60 km/h from the southwest. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

• Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
• Wind slabs may be poorly bonded to the underlying crust.
• Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
• Be mindful that deep instabilities are still present and have produced recent large avalanches.