South Columbia

New snowfall is loading numerous buried weak layers, which is reactive to natural and human triggers and producing slab avalanches. Storm slabs could step down to deeper layers and produce large avalanches. Maintain conservative terrain choices.

Moderate - Intensity of incoming weather systems is uncertain

TUESDAY: Cloudy with snowfall, accumulation 10-15 cm, light to moderate southwesterly winds, alpine temperature near -5 C, freezing level near 1100 m.WEDNESDAY: Partly cloudy with intermittent flurries, light southwesterly winds, alpine temperature near -10 C, freezing level below valley bottom.THURSDAY: Cloudy with snowfall, accumulation 10-20 cm, moderate southwesterly winds, alpine temperature near -7 C, freezing level below valley bottom.

Recent avalanches have been reported on the December 15 layer at and below treeline on all aspects, being triggered naturally, by skiers, and snowmobiles.  The avalanches were small to large, being reported between size 1 and 2 with depths of about 40 cm. This is a consistent trend, with around 5-10 avalanches being reported on this layer each day for the past week.On Monday, numerous natural and skier-triggered storm slab avalanches were reported within the recent 20-40 cm of snow, releasing small to large (size 1 to 2) avalanches at all elevations and on all aspects.  Reports of loading in northeasterly lee features were also noted.Please share your observations through the Mountain Information Network.

20-40 cm of new snow has accumulated on surface hoar in sheltered slopes and a sun crust on steep solar aspects.  The snow has formed a storm slab that has produced numerous avalanches (see the Avalanche Summary).  The snow also fell with moderate to strong southwesterly winds in the alpine, which produced wind slabs in lee features at treeline and alpine elevations.  Below treeline, this new snow is mainly a concern in openings (e.g. cut blocks, gullies, cut banks).The additional snow has created a dangerous slab above numerous buried weak layers. 40-80 cm of snow overlies layers composed of weak and feathery surface hoar. The layers are found most often around and below treeline. This layer has the potential to create easily-triggerable destructive slab avalanches because the layers are buried at a depth prime to human triggering.  See the Avalanche Summary for recent avalanches on this layer.Deeper in the snowpack (90 to 150 cm), a November crust is producing variable test results, from sudden fracture characters to no result.  This layer is considered dormant but could be triggered where the snowpack is thin.