Watch for signs of new wind slab formation on Monday. Alpine winds are forecast to become strong in advance of the storm which is expected to arrive Monday night.
Summary
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
The ridge of high pressure will be displaced by a low pressure system late Monday. A mix of sun and cloud is expected Monday morning and cloudy conditions with light flurries are expected for the afternoon. Alpine wind should be light in the morning and increase to strong during the afternoon. Treeline temperatures are expected to be around -12C. Around 10 cm of snow is expected on Monday night with strong alpine wind from the southwest. Another 5 cm of snow is forecast for Tuesday with moderate to strong alpine wind from the southwest and treeline temperatures around -10C. Unsettled conditions are currently forecast from Wednesday with the possibility of both snow flurries and sunny breaks.
Avalanche Summary
No new avalanches were reported on Friday or Saturday. On Friday, two small whumpfs were felt under wind slabs which were 20 cm thick. On Thursday, ski cutting triggered two size 1 cornices. These did not trigger slabs on the slopes below. On Monday, it is possible that new wind slabs may develop in the afternoon as the wind increases. Old stubborn wind slabs may still be lingering from the strong wind that ended Friday morning and could be hiding under 10-20 cm of low density snow from Saturday.
Snowpack Summary
50-80 cm of snow accumulated over the last week and overlies the mid-December interface which consists of a variety of old snow surfaces including wind affected snow, faceted (sugary) crystals, and/or surface hoar crystals. Recent tests suggest the the new snow is well bonded to the interface in most areas. However, where a spotty layer of surface hoar has been preserved, the interface may still be reactive. In wind affected terrain, the recent storm snow has been redistributed into reactive wind slabs. These wind slabs may now be buried under 10-20 cm of low density snow which fell without much wind on Saturday.The thick mid-November crust layer typically sits 1-2 m down in the snowpack. Recent test results on this layer suggest it is generally well bonded to the adjacent snow with the possible exception of shallow snowpack areas. This layer is considered dormant at this time but remains an isolated concern that we will likely be tracking through much of the season.
rbuhler,
Avalanche Canada
