Uncertainty abounds! Take time to make careful snowpack evaluations, the current early season conditions require a very conservative approach to terrain selection and travel.
This avalanche problem will be found on north aspect terrain in the alpine and at treeline. These avalanches will be localized to zones just below ridge tops and adjacent to flat areas that transition into steeps ( Convex slope ) .
Human trigger avalanches are possible on this slab problem. Around 50 to 90 cm of snow from the past week is forming a slab that is not bonding well to the underlying snowpack. The interface of concern formed during mid-November and is composed of faceted grains, surface hoar, and a hard crust. To date, the layer has been most problematic above 1700 m.
Over the past 48hr period, there has been one avalanche report, this was a skier remotely triggered avalanche that occurred on a north aspect at tree line elevation. The avalanche was size 2 ( large) The important information that has been associated with the snow and avalanche communities reporting has a common theme related to feedback from travel. Widespread whumphing cracking and abrupt settlement are occurring on the very suspect Mid Nov persistence weak layer.
Many previous natural and human-triggered avalanches have been reported in the alpine and at the treeline, between 1700 and 2200 m. The factor of concern is that they are failing on the November 21st / surface hoar facet crust interface.
Additionally, the terrain where these avalanches occurred was steep and focused on north through to east-facing terrain. The size of these avalanches has been from size 1 (small) to size 3 (very large).
One avalanche, in particular, was remotely triggered by a skier and began as a size one and picked up enough mass to strip the snowpack to the ground resulting in a size 2.5 (large) avalanche. Temperatures are forecast to remain cool and I would surmise that this slab avalanche problem will continue to persist.
On the southern border of this region, another remote trigger avalanche was observed at 2080 m. This avalanche size 1.5 (small) failed on the Nov 21 surface hoar/ facets interface and had noted surprising propagation.
During Wednesday's weather event, strong winds from the southwest have affected some areas at treeline and alpine elevations. Many of these areas now present as scoured with some areas stripped to the ground. Expect north aspect terrain to have received additional snow from wind loading.
A series of storms over the past week has delivered 30 to 50 cm of new snow. This snow fell during a period of cooling and is light and easily transported by the wind.
A layer that was buried November 21st can be found down 60 to 90 cm and is primarily a mix of surface hoar and faceted crystals. This layer is the primary concern of persistence and has been the key component of a past natural avalanche cycle.
The average snowpack depth below the treeline is 40 to 70 cm and above that elevation is 100 to 150 cm, with wind-loaded areas presenting as greater than 200 cm.
An Arctic ridge that maintains its presence over the B.C. interior will bring to the area a predominantly clear sky and cool temperatures.
Friday Night
Increasing cloud in the late pm, Light snowfall, accumulation 1 to 2 cm, 40 km/h southwest wind, treeline temperature -18 °C.
Saturday
Clear sky no forecast precipitation, 10 km/h northwest wind, treeline temperature -18 °C rising to -9 °C.
SundayClear sky no forecast precipitation, 10 km/h northwest wind, treeline temperature -12 °C.
MondaySome clouds, Light snowfall, accumulation 1 cm, 10 km/h southwest wind, treeline temperature -10 °C.
More details can be found in the Mountain Weather Forecast.
