One more storm before conditions start to clear for the weekend. Storm slabs are expected to be reactive on Friday, especially in wind loaded alpine areas. Conservative terrain selection remains critical.
Summary
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Friday
Weather Forecast
The last in a series of storm systems will bring snowfall to the region overnight and Friday. 15-25cm of new snowfall is expected between Thursday night and Friday afternoon. Alpine winds are expected to be strong from the south to southwest and freezing levels are forecast to be 1200-1500m. Light snowfall is expected to continue Friday night and should taper off by Saturday morning when a ridge of pressure moves over the region. A mix of sun and cloud is expected for Saturday with light alpine winds and freezing levels around 1000m. Mostly sunny conditions are currently forecast for Sunday morning with a weak storm system arriving Sunday evening.
Avalanche Summary
No new avalanches were reported on Wednesday. On Tuesday, three size 1.5 storm slab avalanches were ski cut on north aspects at 1600m elevation. These slabs were 15-25cm thick and were released on convex roll features. A skier accidently triggered a size 1 storm slab avalanche on a north aspect at 1800m elevation. A few natural size 1.5 avalanches were reported on a west aspect at 2000m and were around 20cm thick. Several solar triggered loose avalanches were also reported from steep sun exposed slopes in the alpine and at treeline. Storm slab avalanches are expected to be remain reactive to human-triggering at higher elevations with ongoing snowfall and wind continuing into Friday. Cornices are reported to large and fragile, and may fail under the weight of a person.
Snowpack Summary
40-80cm of new snow has accumulated in the last week and overlies a thick melt-freeze crust which extends into the alpine. The snow is reported to be bonding well to the crust and recent avalanches have been failing within the recent storm snow, not on the crust interface. At treeline and below, other crusts may exist in the upper snowpack due to the recently fluctuating freezing levels. Freezing levels on Wednesday climbed to around 2000m and have to fallen to around 1400m on Thursday afternoon. As the freezing level continues to drop, a crust is expected to form at lower elevations. Ongoing southeast through southwest winds have been loading leeward features in the alpine and large cornice development has been reported over the last few days. The weak surface hoar layer from early January can be found down over a meter and is still reactive in isolated snowpack tests but triggering an avalanche on this layer has become unlikely.
rbuhler,
Avalanche Canada
