Avalanche Forecast
Regions: Little Yoho.
Freezing levels will rise on Sunday, with 5-10 cm of new snow and strong SW winds expected Sunday night and into Monday. Hazard will increase later on Sunday and into Monday as the storm arrives.
Confidence
Moderate
Avalanche Summary
No new avalanches were observed in the Yoho area during a flight on Saturday. One previous skier-triggered avalanche was observed on a SE aspect on Mt Collie failing on a buried crust. Lots of debris is still present from the natural avalanche cycle on April 11-12.
Snowpack Summary
Recent storm snow has settled to 20-30 cm above 2300 m. The storm snow sits over buried sun crusts that are present to ridge crests, and faceted layers on shady aspects. Multiple buried crusts are present in the top 50-70 cm on solar aspects. The basal depth hoar is present but is only a concern in thin areas. Low elevations have a temperature crust on all aspects.
Weather Summary
On Sunday, winds will gradually increase into the moderate to strong range out of the SW. Freezing levels will start to rise, reaching 2100-2300 m late in the day. Precip will start in the late afternoon with 5-10 cm expected overnight and into Monday and rain is possible at valley bottom elevations.
Terrain and Travel Advice
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
Avalanche Problems
Storm Slabs
20-30 of storm snow has formed slabs over previous crusts and facets. While the storm snow has started to bond, it may still be possible to trigger a slab at this interface in steep terrain especially with increasing temperatures or solar heating.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2.5
Loose Wet
Freezing levels will rise on Sunday, and while solar inputs may be limited, there is still potential for small wet loose avalanches, especially if we get rain at lower elevations later in the day.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 2
Deep Persistent Slabs
The November basal facets and depth hoar have been mainly dormant in this region and we have seen few avalanches on this layer. The recent storm was a good test. Thin spots or places exposed to large loads like cornices are the greatest concern.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 4