Avalanche Forecast

Moderate - Wind effect is extremely variable

A weak frontal system moves through the region on Monday and is expected to bring 2-6 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, explosives triggered several persistent slab avalanches up to size 2.5 in the Bugaboos area above 2600 m elevation but details are very limited.  It appears that one stepped down to the mid-November crust and several released on the ground.  One explosive triggered size 1.5 wind slab avalanche was also reported from the Dogtooth range which had a slab thickness of 20 cm.  On Friday, explosives triggered numerous storm slabs up to size 2.5 plus one size 3. These slabs were typically 30-60 cm thick and were reported on most aspects. On Wednesday and Thursday, a natural avalanche cycle up to size 2.5 was observed. During the storm, only one natural avalanche was observed to have stepped down to a deeper layer. 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.

25-60 cm of recent storm snow typically overlies the variable mid-January interface which consists of wind affected surfaces in exposed terrain, surface hoar in sheltered areas, and/or widespread faceted old snow. The bond between the new snow and the old surface is generally gaining strength with 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 50-100 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 an isolated concern for shallow snowpack areas where the layer is closer to the snow surface.