Avalanche Forecast
Issued: Mar 17th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Loose Wet.
mbender,
Avalanche Canada
UPDATE ON SATURDAY AT 7:15 AM: See the avalanche summary for a notable avalanche that occurred yesterday.
There is uncertainty with the freezing level and the amount of cloud cover on Saturday. Certainly if the sky remains clear we may see the warmest day this week. Minimize your exposure to steep slopes facing the sun during the hottest part of the day.
Summary
Confidence
High
Avalanche Summary
A snowmobile triggered a large persistent slab avalanche (size 2.5) in the south Purcells on Friday afternoon. The avalanche occurred in burnt forested terrain on a south aspect at 2200 m. It failed on a 50 to 100 cm deep layer that is suspected to be a sun crust buried in February.
On Thursday in the Elk Valley there were reports of several size 3 explosives triggered and natural wind slab avalanches that stepped down to a deeply buried weak layer of facets. These avalanche were triggered at the upper end of treeline and in the alpine and were mostly in cross-loaded terrain features on west and northwest aspects.
On Wednesday, a skier accidental size 2 wind slab avalanche was triggered near St. Mary's. The avalanche occurred on a northeast aspect at treeline and stepped down to the basal facets. For photos and more details check out the MIN report.
If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.
Snowpack Summary
20-40 cm of wind-affected storm snow falling earlier in the week can be found above 1400 m. This sits on a thin sun crust on solar slopes and wind affected snow in open areas. Below 1400 m a rain crust covers the surface.
In the Purcells around St Mary's, several weak layers from Jan and Feb can be found down 50 to 120 cm. The mid-snowpack is generally well-settled.
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
Friday Night
Mainly clear. Treeline temperature -9 °C. Wind light southwest. Freezing level at valley bottom.
Saturday
Mainly sunny with cloudy periods. Treeline temperature near 0 °C. Wind light southwest. Freezing level rising to 2000m.
Sunday
Mix of sun and cloud. Treeline temperature -1 °C. Wind light southeast. Freezing level rising to 2000m.
Monday
Mainly cloudy with scattered flurries. Treeline temperature -4 °C. Wind light east. Freezing level 1500m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be especially cautious as you transition into wind affected terrain.
- Seek out sheltered terrain where new snow hasn't been wind-affected.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Southwest winds have redistributed storm snow from earlier in the week to build wind slabs in alpine and treeline lees. Although natural avalanche activity has tapered off wind slabs remain possible to human trigger.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
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.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Wet
Steep rocky terrain facing the sun is likely to see thin loose wet avalanches release during the heat of the day.
Aspects: South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 18th, 2023 4:00PM
