South Columbia

Lingering wind slabs are expected to be the main concern on Monday. Use extra caution in wind affected terrain.

Moderate - Wind effect is extremely variable

A weak frontal system moves through the region on Monday and is expected to bring 2-8 cm of snow with the largest amounts in the south of the region. Alpine wind is expected to be light from the south in the morning switching to the north in the afternoon. Afternoon freezing levels are forecast to be around 1000 m with treeline temperatures around -5C. A mix of sun and cloud is expected for Tuesday and Wednesday. Alpine wind is forecast to remain light from the north and treeline temperatures are expected to be around -10C.

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 Friday, a couple natural size 2 cornice releases triggered wind slabs. These were at around 2500 m elevation on northeast and east aspects. Several skier triggered storm slabs and wind slabs up to size 1.5 were also reported. Explosives also triggered one size 3 storm slab. All this activity was the recent storm snow releasing on the old surface and the slabs were 20-60 cm thick. On Wednesday and Thursday during the storm, widespread natural avalanches up to size 3 were being observed. On Monday, lingering wind slabs are expected to be the main concern. These should be expected in wind exposed terrain on aspects loaded by the recent southwest wind.

20-50 cm of recent storm snow typically overlies the variable mid-January interface with the largest snowfall amounts in the north of the region. The buried interface consists of 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 is generally gaining strength with the colder temperatures that followed the storm but weaknesses are lingering, especially where surface hoar is preserved. Strong southwest winds during the storm and moderate southwest winds following the storm have redistributed the new snow and developed wind slabs in leeward terrain features. 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. The lower snowpack is well bonded and features a thick rain crust near the ground.