Dangerous avalanche conditions exist at higher elevations where new snow and strong winds are building fresh, reactive storm slabs and adding additional load to buried weak layers.
A weak layer found down 80 to 120 cm has been the culprit of recent very large avalanches in the region. With additional snow and wind we may see more large avalanche activity on this layer on Tuesday. Avoid exposure to overhead hazards.
As snowfall accumulates, expect a more widespread and reactive slab to form. Be especially cautious in lee wind-affected terrain where winds have redistributed snow into deep cohesive pockets.
On Sunday, a few natural, size 2, wind slab avalanches were reported. Wind slab activity was observed in cross-loaded terrain on west aspects in the alpine.
On Saturday, a very large (size 4) avalanche was reported on Joffre shoulder. It was observed from a distance so it is hard to determine what layer this avalanche failed on however we suspect it to be the weak layer of facets or surface hoar overlying a crust at the base of the snowpack.
By Monday morning 10 to 20 cm of snow and strong winds will have built fresh slabs at higher elevations. New snow overlies 30 to 60 cm of settling snow and wind affected surfaces.
A prominent crust varying in thickness is found at treeline and below, 40 to 80 cm down. In some areas, a layer of preserved surface hoar is found just above the crust.
Another weak layer of facets or surface hoar overlying a crust is found at the base of the snowpack down 80 to 120 cm. This is the suspected failure plane for a few large avalanches in the region that occurred on January 6.
Snowpack depths are 100 to 140 cm at treeline and decrease rapidly below.
Monday Night
Cloudy with flurries, 10 to 20 cm of snow. Southwest ridgetop winds 30 to 70 km/h. Treeline temperature -8 °C.
Tuesday
Cloudy with flurries, 5 to 10 cm of snow. West ridgetop winds 20 to 40 km/h. Treeline temperature -9 °C.
Wednesday
A mix of sun and cloud with isolated flurries, trace amounts of snow. Northwest ridgetop winds 10 to 30 km/h. Treeline temperature -12 °C.
Thursday
Partly cloudy with isolated flurries, up to 3 cm of snow. Southwest ridgetop winds 20 km/h. Treeline temperatures drop through the day to -18 °C.
More details can be found in the Mountain Weather Forecast.
