Buried surface hoar layers from early January remain at an ideal depth for rider triggering. Traffic may have reduced the reactivity of this weakness on our more popular runs, but approach terrain that is off the beaten path with extra caution.
Cold temperatures are adding to the risks of backcountry travel, bring extra layers and leave yourself a little extra buffer to get out safely at the end of the day.
Windslabs could be lurking anywhere, with outflow (North) winds reverse loading slopes early on Saturday, and previous strong SW winds having built slabs earlier in the week. If triggered, wind slabs may step down to the persistent surface hoar layers.
This layer has been most reactive around treeline, in areas that have not seen significant skier traffic since early January.
After a long period of dormancy in the park, there was a large cornice triggered natural avalanche in the past 24hrs on this low probability/high consequence layer (see avalanche summary).
The arctic ridge of high pressure will remain over our area until late Monday.
Tonight: Mostly clear, Alpine Low -21*C, Light NE ridgetop winds.
Sunday: Mostly Sunny. Alpine High -18*C. Light NW winds.
Monday: Cloudy periods, isolated flurries. Low -18*C, High - 15*C. Light W wind.
Tuesday: Cloudy with isolated flurries. Low -15*C, High -12*C. Light SW wind.
On Saturday, there was a large (size 3) cornice triggered deep slab avalanche from the South East slopes of Grizzly peak. Strong Northerly winds are the suspected trigger. There was also a small (size 1) skier triggered avalanche on a steep roll mid-way down Avalanche crest.
Artillery control on Friday produced numerous size 2-2.5, and a few size 3, slab avalanches in the Alpine and at Treeline. These are suspected to have been primarily windslabs, with some propagating more widely, suggesting failure on the early January surface hoar. These avalanches started as fast moving powder clouds, but quickly ground to a halt when they hit the refrozen snow mid-track (~1700m).
On Wednesday, a Skier triggered an avalanche on McGill shoulder,the failure plane for this was suspected to be an early January surface hoar layer down 50cm.
Watch for fresh wind slabs in strange places from outflow (Northerly) winds. There were also previous wind slabs at upper elevations from strong SW winds.
Warm temps this week have left a surface crust below ~1700m, and a buried sun/temperature crust (Jan 21st) on steep south facing terrain, down 30-40cm around treeline.
The early January Surface Hoar layers (Jan 3rd and 12th), are buried down 40-70cm, and most likely to be rider triggered at treeline.
Large facetted crystals and the November 17th facet/SH/crust weakness can still be found near the base of the snowpack in many areas.
