South Columbia

Snowfall is expected to continue in the coming days with associated moderate to strong southwesterly winds. The new snow is falling on numerous weak layers and will likely be reactive to natural and human triggers. Cautious route finding is advised.

Moderate - Intensity of incoming weather systems is uncertain

MONDAY: Cloudy with light snowfall, accumulation 5-10 cm, moderate to strong southwesterly winds, alpine temperature near -4 C, freezing level near 800 m.TUESDAY: Cloudy with snowfall, accumulation 10-15 cm, light to moderate southwesterly winds, alpine temperature near -5 C, freezing level near valley bottom.WEDNESDAY: Partly cloudy with intermittent flurries, accumulation 2-5 cm, light to moderate southwesterly winds, alpine temperature near -10 C, freezing level below valley bottom.

Recent natural, skier-triggered, snowmobile-triggered, and skier-remoted avalanches have been reported on the December 15 layer at and below treeline on all aspects.  The avalanches were small to large, being reported between size 1 and 2 with depths of about 40 cm. Numerous reports of whumphing were also noted in low elevation cutblocks and flat terrain.Numerous natural and explosive-controlled storm slabs were also noted within the recent 10-30 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.

15-30 cm of new snow has accumulated on surface hoar in sheltered slopes and a sun crust on steep solar aspects.  The snow is forming a storm slab, which may not bond well to the underlying layers.  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 could create a dangerous slab above buried weak layers.  40-80 cm of snow overlies two layers composed of weak and feathery surface hoar (buried on December 27 and December 15). The layers are found most often around and below treeline. As the overlying snow forms a cohesive slab, this layer has the potential to create easily-triggerable destructive slab avalanches.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.