The recent storm snow is expected to be touchy on Wednesday, especially in wind loaded terrain. Conservative terrain selection remains critical.Use extra caution around steep south facing slopes if the sun comes out in full force.
Summary
Confidence
Moderate - Freezing levels are uncertain on Thursday
Weather Forecast
A mix of sun and cloud is expected on Wednesday with moderate alpine wind from the west and treeline temperatures around -12C. The next storm system is expected to arrive Wednesday night with models currently showing 5-10 cm of snowfall by the end of day on Thursday. Alpine wind is forecast to become strong from the southwest and freezing levels are forecast to rise as high as 2000 m. Light snowfall is forecast to continue on Friday with strong alpine wind from the southwest.
Avalanche Summary
On Monday, numerous skier triggered storm slab avalanches size 1-1.5 were reported. Explosives also triggered storm slabs up to size 2.5. These slabs were typically around 30 cm thick. One of these storm slab avalanches stepped down to the basal weakness resulting in a slab that was up to 150 cm thick. On Monday in the Lizard region, natural avalanches up to size 2.5 were observed. The recent storm snow is expected to remain touchy on Wednesday, especially where it has been redistributed by the wind. If the sun comes out in full force, solar triggered avalanches are possible on south facing slopes. Storm slab avalanches also have the potential to step down to the basal weakness which would drastically increase the size and destructive potential of a resulting avalanche.
Snowpack Summary
Up to 90 cm of new low density storm snow has accumulated over the weekend. Strong shifting winds have redistributed the new snow in exposed terrain forming very touchy wind slabs. The new snow overlies a highly variable old surface which may include wind affected surfaces, facets, and/or a rain crust below around 1500 m. Recent reports suggest a poor bond between the new snow and the old surface. In deeper areas, the snowpack appears to be well settled with isolated concerns about the mid-December facet layer which was buried 50-100 cm deep prior to the weekend storm. In shallow snowpack areas and at lower elevations, the snowpack is weak, faceted, and has no structure. Prior to the storm, it was possible to step onto the snow surface in these areas and sink right to the ground.
rbuhler,
Avalanche Canada
