Avalanche Forecast

Moderate -

FRIDAY NIGHT: A weak front passes overnight bringing 5-10 cm of snow, strong wind out of the southwest, freezing level dropping from 1400 to 800 m, alpine temperatures around -4 C.SATURDAY: Clearing throughout the day, strong wind out of the west, alpine high temperatures around -4 C.SUNDAY: Increasing cloud throughout the day, moderate to strong wind from the southwest, alpine high temperatures around -2 C.MONDAY: Light flurries, strong wind from the southwest, freezing level rising to 1700 m.

Evidence of a natural avalanche cycle was observed on Friday, including size 2 avalanches failing on storm snow in alpine terrain. Explosives triggered several large avalanches (size 2-3) in the storm snow on north to east aspects between 1800 and 2100 m. Some of these avalanches propagated long distances across terrain, suggesting the snow has a poor bond to the old snow interface.Reports from Thursday indicate the storm snow was also very reactive to human triggering, as it produced several small avalanches (size 1) in mellow terrain that were triggered from a remote distance. See this MIN report.Another recent notable avalanche was a size 2 human triggered avalanche on December 2 in Cornice Bowl north of Fernie. It occurred on a northwest facing feature at 2300 m and ran on a crust layer. There are good photos in this MIN report.

Storm snow totals continue to accumulate with another 5-10 cm expected on Friday night. Roughly 30-50 cm of recent storm snow now sits above a weak layer composed of large surface hoar crystals and/or sun crust. There have been numerous signs of the new snow bonding poorly to this layer including remote triggering from low angle terrain, shooting cracks, and wide propagations in avalanches. Aside from storm slabs now blanketing the surface, a primary concern is the combination of weak facets and crusts in the bottom half of the snowpack. The crust is most prevalent at and above treeline and is likely most problematic on north-facing features, especially those that are large and planar in nature. A layer of large surface hoar can also be found at similar depths in some areas, as found in a recent MIN report here.