Avalanche Forecast
Regions: Little Yoho.
Forecasters remain concerned about the potential for human triggering of the buried facet layer at the base of the snowpack. Continued discipline in sticking to mellower terrain with low consequences is the most reliable method of reducing risk in these conditions.
The deep persistent slab problem in particular has shown potential for long propagations and remote triggering even below treeline.
Confidence
Moderate
Avalanche Summary
No new natural avalanches were reported or observed on Saturday or Sunday. Skier triggered whumpfing and cracking continue to occur in many places. Local ski hills have had explosive triggered avalanches up to size 2 on both of the buried facet layers near the base of the snowpack in the past several days.
Snowpack Summary
Some wind-affected snow on alpine and treeline ridgetops. 10-20 cm of softer surface snow sits over a denser mid-pack which has formed a slab over the weak facet layers below. The December 17 persistent layer of surface hoar/facets is down 25-60 cm and becoming less reactive. The November 16 deep persistent layer of facets, depth hoar, and/or sun crusts is found near the base of the snowpack with test results continuing to show sudden failures.
Weather Summary
A mix of sun and cloud with light flurries along the divide will continue into Monday. Winds will increase from the SW on Sunday night before dropping back to the light-moderate range on Monday. Temperatures will remain relatively mild on Monday, with daytime highs near -3°C at the valley bottom and alpine temperatures between -8 and -12°C.
Terrain and Travel Advice
- Uncertainty is best managed through conservative terrain choices at this time.
- Use careful route-finding and stick to moderate slope angles with low consequences.
Avalanche Problems
Deep Persistent Slabs
The lower snowpack is comprised of very weak facets, with the mid and upper snowpack forming a slab over these facets at all elevations. This weak basal layer is fairly uniform across most of the terrain and has shown the potential for human triggering, long propagations and remote triggering.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 2 - 3
Persistent Slabs
The December 17 layer of persistent weak facets that formed during the prolonged deep freeze in early December is down 30-60 cm. This layer appears to be gaining strength, but is still worth considering. If a failure initiates on this layer, it may step down to the deep persistent layers resulting in larger avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2