Avalanche Forecast
Issued: Apr 9th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Persistent Slabs and Deep Persistent Slabs.
rgoddard,
Avalanche Canada
Forecasted weather will bring heavy precipitation and strong winds to much of our region and will increase the avalanche hazard.
The chance of avalanches is very likely today.
Make conservative choices and back off if you see signs of instability.
Summary
Confidence
Avalanche Summary
Storm slab avalanches were reported on Saturday. Most of these were triggered with the use of explosives but there were some naturals. These were no bigger than a 1.5 and occurred on north-to-east facing slopes at a depth of about 30 cm. Saturday also witnessed some natural wet loose and cornice avalanches up to size two. More of these types of avalanches are expected on Monday.
Friday saw wind slab and storm slab avalanches. The wind slab avalanches were triggered remotely and with ski cuts. Both were in the alpine, on northerly aspects, and were 30 cm deep running on facets that were buried on April 1st. In the northern part of our region, there was a size 2 natural storm slab avalanche. This occurred in the alpine on an east-facing slope and also failed on a surface that was buried 30 cm down.
On Wednesday, storm snow continued to be reactive to natural and human triggers. A few surprise skier-triggered storm slab avalanches were reported up to size 2. Naturally triggered storm slab and wind slab avalanches were observed up to size 2.5. Many of these avalanches are reported to be failing on a surface hoar layer buried near the end of March or a crust on solar aspects. Avalanche activity has primarily been observed on north and east aspects from 1700 to 2200 m. Reports indicate that the Selkirks seem to be the most reactive with rider remote-triggered slabs in the upper 50 cm of snow. During this storm, avalanches such as these will be something to look out for.
Snowpack Summary
New snow falling Sunday night and into Monday will be redistributed into wind slabs by southwest winds. Snowfall amounts will vary in our region today but new storm slabs and wind slabs will sit on a variety of surface snow. In sheltered areas, it will rest on 20 to 40 cm of snow that has been settling since last week.
On southerly aspects and below treeline, there is a widespread cust buried 30 to 50 cm down. On north-facing slopes at treeline and above there may exist a layer of faceted snow or surface hoar in shelter areas. Further down in the snowpack, around 60 cm, a surface hoar layer has been reactive to human triggering. This has occurred primarily in the Selkirks, on northeasterly slopes from 1700 m to 2100 m. Wednesday was the last day that there was any real activity on this layer but this storm may change that.
The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.
Weather Summary
Sunday Night
Cloudy, 8 to 13 cm accumulation of snow and rain, winds southwest 30 to 40 km/h gusting to 80, freezing levels between 1500 and 2000 m.
Monday
Cloudy, 10 to 20 cm accumulation with highest amounts in the south, winds southwest 20 to 30 km/h gusting to 50, freezing levels as high as 2000 m, and cooling throughout the day.
Tuesday
Mostly cloudy with potential late day clear periods, 5 to 10 cm accumulation by morning with another 5 cm during the day, winds southwest 20 to 30 km/h gusting to 40, freezing levels to 1500 m.
Wednesday
Cloudy with sunny periods, trace accumulation, winds west 25 to 25 km/h, freezing level starting at 500 and climbing back up to 1500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Watch for fresh storm slabs building throughout the day.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Seek out sheltered terrain where new snow hasn't been wind-affected.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
Problems
Storm Slabs
Some areas of our region may see up to 40 mm of precipitation by Monday night. Warm temperatures will have this fall as rain at lower elevations and as heavy wet snow at higher elevations. Moderate to strong southwest winds all also associated with this storm. The highest amounts of precipitation will be in the West Purcells and in pockets near Revelstoke.
Whether it is rain, heavy snow, or a large wind deposit of snow, avalanche activity is expected to increase.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A weak layer from late March is found down 50 cm and is responsible for a number of recent human triggered and natural avalanches in the region. With incremental loading through the next few days watch for signs that this layer may be becoming more reactive in the terrain around you.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A weak layer of facets exists near the base of the snowpack. The likelihood of human triggering is low given the layer's depth.
Suspect terrain for human triggering includes steep, shallow, and rocky terrain where the snowpack transitions from thin to thick.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 10th, 2023 4:00PM
