Avalanche Forecast
Issued: Feb 16th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
jpercival,
Avalanche Canada
Expect to encounter increasingly sensitive wind slabs as the incoming storm adds more mass to an already established avalanche problem. Seek well support low angle terrain that avoids steep lee aspect wind-loaded areas.
Carefully evaluate wind loading as you move through terrain and investigate the bond of wind slabs to the crust below.
Summary
Confidence
Avalanche Summary
On Tuesday, A snowmobiler remote triggered a size 2 persistent avalanche in the Callaghan. The avalanche was reported to be triggered from 10 m away and was adjacent to a heavy traffic area. We suspect this avalanche slid on the mid-January persistent weak layer. See the MIN for details and photos. This is the latest human-triggered avalanche on this persistent weak layer in the region.
For more evidence of this weak layer see this MIN report from last Wednesday when a rider at Chocolate Bowl triggered a size 2.5 persistent avalanche. Find another example in this MIN from a skier accidental size 2 persistent slab avalanche that occurred on Saturday.
On Monday afternoon, search and rescue technicians responded to a fatal avalanche incident north of the Sea to Sky region. The avalanche is believed to have occurred on Saturday and was initiated in a shallow rocky area. See the MIN for more details.
Snowpack Summary
An incoming storm is expected to bring another 10 to 20 cm of new snow. This will be in addition to up to 30 cm of past storm snow. Expect the wind to redistribute this over a variety of surfaces including facets, old wind slabs, and a thin breakable crust below 1650 m. In sheltered areas above 1200 m snow remains dry and unconsolidated.
Two concerning crusts are found in the mid-pack at varying depths and are widespread throughout the region. A crust from late January is found at all elevations down 40-100 cm with small facets above it. In the Rhododendron and Pemberton Icefield area, this crust has been reactive to rider traffic and in test pits at treeline. In the Brandywine area, a crust found 80-200 cm deep resulted in a few surprisingly large rider-triggered avalanches last week. This layer exists to 1900 m in these areas.
Total snowpack depths are approaching 300 cm in some areas.
Weather Summary
Thursday Night
Mainly cloudy with snowfall, 5 to 10 cm accumulation. Winds southwest 20 km/h gusting to 50 km/h. Treeline temperature -12 °C. Freezing level 200 m.
Friday
Cloudy with light snowfall, 1 to 5 cm of accumulation. Winds Northwest 20 km/h gusting to 50 km/h. Treeline temperatures -8 °C and freezing levels of 600 m.
Saturday
Partly cloudy with isolated flurries, 1 to 5 cm accumulation. Winds northwest 5 km/h gusting 30 km/h. Treeline temperature -6 °C. Freezing level 700 m.
Sunday
Partly cloudy with isolated flurries, 1 to 5 cm accumulation. Winds northwest 20 km/h gusting 60 km/h. Treeline temperature -6 °C. Freezing level 700 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Fresh wind slabs will likely form throughout the day, diligently watch for changing conditions.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Be alert to conditions that change throughout the day.
Problems
Wind Slabs
Southwesterly winds are distributing available snow into fresh wind slabs on north through to east slopes in the alpine and upper treeline. Wind slabs may be sitting on a crust making them especially reactive to ridder triggering.
Previously northerly winds built wind slabs in exposed alpine features. Continue to use caution around these features and watch for areas that have been reverse-loaded and cross-loaded.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Two weak layers consisting of a crust with small facets found above them have been reactive to rider traffic in the last week. The first, down 40-100 cm has been reactive at treeline in the Rhododendron and Pemberton Icefields area. The second is found up to 1900 meters and is down 60-150 cm in the snowpack. It has been reactive to human triggering in the Brandywine and Callaghan area on north and west aspect between 1800 and 1600 m. Both of these layers seem like isolated problems at the moment but if triggered they will result in large consequential avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 17th, 2023 4:00PM
