Avalanche Forecast

Over the past 24hr period, there have been no new avalanches observed or reported. 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 new snowfall Tuesday and Wednesday brought to the region between 10 to 20 cm of new snow. 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 the recent 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.

A strengthening Arctic ridge over the B.C. interior will bring to the area a clearing sky and cool temperatures.

Thursday Night

Clear sky no forecast precipitation, 20 km/h northwest wind, treeline temperature -10 °C to -15 °C.

Friday

Clearing sky with some possible isolated afternoon flurries, accumulation a trace to 2 cm, 10 km/h southwest wind, treeline temperature -18 °C rising to -15 °C.

Increasing cloud in the early am, Light snowfall, accumulation 1 to 5 cm, 50 km/h southwest wind, treeline temperature -15 °C rising to -8 °C.

Clear sky no forecast precipitation, 20 km/h northeast wind, treeline temperature -18 °C rising to -4 °C.

More details can be found in the Mountain Weather Forecast.

• Choose simple, low-angle, well supported terrain without convexities.
• Make observations and assess conditions continually as you travel.
• Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.