Watch for wind slabs at ridge crests and in cross loaded features. Deeply buried weak layers also remain a concern as conditions improve. Play it safe in simple terrain with reduced exposure. Avoid thin and rocky start zones where deep layers are closer to the surface.
Moderate west and southwest winds continue to build wind slabs in the alpine and treeline. Watch for reactive wind slabs around ridges and loaded terrain features. Slab will be most reactive if they sit on a smooth crust.
A reactive surface hoar layer exists 30-70cm deep in the Toby Creek drainage and surrounding areas. It is most prevalent between 1900-2400m. This interface may result in large avalanches with wider propagation and slabs that are more sensitive to human triggers.
A weak and reactive layer of facets and depth hoar exists at the base of the snowpack above 1900m. While this layer sits deep in the snowpack it has the potential of producing large and destructive avalanches.
Avoid thin and rocky start zones where this layer may sit closer to the surface, and big open slopes capable of producing large avalanches.
Snow returns to the interior on Tuesday evening as cold temperatures continue.
MONDAY NIGHT: Partly cloudy with no snowfall expected. Moderate westerly winds. Freezing level valley bottom.
TUESDAY: Increasing cloud with isolated flurries. Moderate to strong southwest winds. Alpine high temperature -10 C. Freezing level valley bottom.
WEDNESDAY: Snowfall begins Tuesday evening, with light accumulations building over Wednesday (up to 5cm), with strong westerly winds. Freezing level below 1000m, alpine highs of -10.
THURSDAY: Cloudy with flurries throughout the day. Winds ease to moderate westerlies. Freezing levels at valley bottom. Alpine highs of -8.
The snowpack is complex with several reactive persistent weak layers in the mid and lower snowpack.
Explosive control work near Golden yesterday produced a size 2 slab avalanche that failed to ground in a steep and unsupported terrain feature. A naturally triggered size 3 was also observed on a west facing slope in the Northern zone of the Purcells, believed to have occurred around the 2nd of December.
Two Mountain Information Network (MIN) reports (MIN 1 and MIN 2) from Friday, Dec 3 in Quartz Creek report deep persistent avalanches failing at the base of the snowpack. These observations highlight the weak and reactive snow at the base of the snowpack.
A MIN report submitted on Sunday Dec 5 from the Brewer Creek area reported a column test failure on the Nov 21 SH down 60cm. Several recent avalanches that occurred in the Toby Creek drainage are thought to have failed on the same layer. This is believed to be lurking around the Toby Creek drainage area, however data is sparse this early in the season and this layer is believed to extend to other areas.
10-40cm of low density snow sits over a supportive crust from the recent rain event on all aspects below 2400m. Westerly winds have redistributed new snow into deeper deposits in wind loaded features at higher elevations.
A surface hoar layer extends throughout the Toby Creek drainage and surrounding areas - down 30 to 70 cm in sheltered features at treeline and below. Recent snowpack tests have shown this layer to produce sudden propagating fractures. We have limited knowledge of the distribution of this layer, but suspect is its most active between 1900-2400m.
A late October facet/crust layer of concern sits at the bottom of the snowpack above 1900m. This layer has been reactive to human and explosive triggers, producing large avalanches. This layer is widespread throughout the region and will likely continue to be a layer of concern.
Average snowpack depth at treeline is 100-180cm, with the deepest snowpack found near the Bugaboos.
