South Columbia

Fair - Due to the number of field observations

A strong Arctic air mass will continue to dominate conditions in the southern interior. Thursday: Mostly sunny, light NE alpine winds, alpine temperatures around -20CFriday/Saturday: Mostly sunny, light NE alpine winds possibly increasing on Saturday, alpine temperatures as low as -30C

Several natural avalanches to size 2.5 were recently reported across the forecast region on all aspects.  These avalanches primarily consist of the previous storm snow or redistributed wind slabs sliding on the late-November crust/surface hoar interface. 

Snowpack depths are typically 100-140 cm at treeline elevation. The previous storm snow (~30-60cm) overlies the late-November interface which typically consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. These weak layers are expected to be persistent and will continue to create avalanche problems in areas with enough overlying snow. The current cold temperatures will contribute to the persistence of this weak layer.  Strong NE winds after the storm have caused reverse loading and wind slab formation on SE through W aspects in wind exposed areas.  There are two layers of concern within the mid/lower snowpack but these have recently become inactive: the early November surface hoar is roughly 60cm above the ground and the October rain crust is at the base of the snowpack. While these layers have recently become inactive, residual risk of large, destructive avalanches exists, especially in areas with a thinner snowpack. The October crust can be found in the alpine on north aspects and the early November surface hoar appears to be isolated and drainage specific.