Avalanche Forecast
Issued: Mar 12th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Deep Persistent Slabs and Persistent Slabs.
lbaker,
Avalanche Canada
Warm temperatures, new snow and strong winds will create very dangerous avalanche conditions on Monday.
Uncertainty is best managed by conservative terrain choices at this time. Avoid shallow areas where triggering the deep persistent weak layer is more likely.
Summary
Confidence
Moderate
Avalanche Summary
On Saturday, a natural size 2.5 was observed at 2400 m on a northwest aspect. The avalanche was +100 cm deep and occurred on one of the persistent buried layers within the snowpack.
Incoming snow and rising freezing levels will increase the likelihood of avalanches throughout the day tomorrow. Large avalanche activity on the deeply buried weak layers is expected tomorrow with weather inputs.
Snowpack Summary
Storm snow accumulates over a plethora of surfaces including hard, wind-affected surfaces in open areas, surface hoar and facetted snow in sheltered areas and a sun crust on steep solar slopes.
Buried surface hoar sits 50-70 cm deep in sheltered terrain features, and a thin sun crust exists at the same depth on steep south-facing terrain. Several other layers from January can also be found in the top 100cm of the snowpack.
The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. this weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.
Weather Summary
Sunday Night
Partly cloudy with isolated flurries. the Western Purcells could see up to 10 cm while the rest of the region sees trace accumulations. Alpine temperatures reach a low of -6 °C. Ridge wind light from the south.
Monday
Cloudy with mixed precipitation, 5-20 cm of new snow accumulation at higher elevations. Alpine temperatures reach a high of -4 °C. Ridge wind southwest 25-40 km/h. Freezing levels rise to 1700 meters.
Overnight flurries continue bringing an additional 10-15 cm of snow to the Western Purcells.
Tuesday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -9 °C. Light ridge wind from the southwest. Freezing levels rise to 1200 meters.
Wednesday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -7 °C. Light ridge wind from the west. Freezing levels rise to 1300 meters.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Make conservative terrain choices and avoid overhead hazard.
- Avoid areas with a thin or variable snowpack.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Storm Slabs
Warm temperatures, new snow and strong southwest winds will build reactive storm slabs on Monday. Be extra cautious on exposed north and east slopes as they will likely have the deepest and most reactive storm slabs.
If triggered, storm slab avalanches may step down to deeper weak layers resulting in large avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human triggered avalanches are possible at treeline and above. Avoid shallow and rocky areas, where the snowpack depth is highly variable. This is a very concerning avalanche problem and should stay in your mind when traveling in the backcountry.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Numerous weak layers from January and February exist at all elevations on a variety of aspects. On shaded slopes, these layers generally present as surface hoar, and on sun-exposed slopes they present as facets and a crust.
Avalanches triggered on these layers can step down to the facets at the bottom of the snowpack resulting in a very large avalanche.
These layers can be remotely triggered. Avoid traveling below steep slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Mar 13th, 2023 4:00PM
