Avalanche Forecast

Moderate - Wind effect is extremely variable

Mostly cloudy conditions are expected on Tuesday with light alpine wind from the north and the possibility of light isolated flurries. Afternoon freezing levels are forecast to reach around 800 m with treeline temperatures around -6C. A mix of sun and cloud is expected for Wednesday and Thursday. Alpine wind is expected to remain light from the north and treeline temperatures are forecast to be around -8C.

On Sunday, a natural size 2.5 avalanche was reported in steep cliffy terrain on a south aspect at 2100 m elevation. Skiers triggered two storm slab avalanches on steep south and southwest aspects. These both had a typical slab thickness of 40 cm and one of the avalanches resulted in a partial burial. Explosives also triggered a few storm slab avalanches on north and east aspects which were 15-20 cm thick slabs. On Saturday, skiers were triggering a few small size 1 wind slabs in wind loaded terrain features resulting from recent moderate southwest wind. One natural size 1.5 cornice release was also observed. On Tuesday, lingering wind slabs are expected to be an isolated concern. These should be expected in steep and unsupported or convex wind loaded terrain features.  In some areas, moderate outflow winds may have caused reverse loading and formed thin new wind slabs.

20-50 cm of recent snow typically overlies the variable mid-January interface with the largest amounts in the north of the region. The buried interface consists of old wind affected surfaces in exposed terrain, surface hoar in sheltered areas, widespread faceted old snow, and/or a sun crust on steep solar aspects. The bond between the new snow and the old surface has generally gained a lot of strength with the colder temperatures that followed the storm but weaknesses may still be lingering, especially where surface hoar is preserved. Strong southwest winds during the storm had redistributed the new snow and developed wind slabs in leeward terrain features.  Isolated moderate outflow winds may have more recently resulted in reverse wind loading.The mid-December facet/surface hoar persistent weak layer can be found buried 70-120 cm deep and is generally considered dormant. However, we are still receiving occasional reports of sudden results in snowpack tests, suggesting that it has to potential to propagate into a large avalanche if triggered. This layer remains a concern for shallow snowpack areas where the layer is closer to the snow surface.