Avalanche Forecast
Regions: Little Yoho.
Large explosive triggered avalanche occurred today. The potential for very large human triggered avalanches on the weak facets remains high. Avoid exposure to overhead hazard and stick to moderate angled supported terrain to enjoy the new snow.
Weather Forecast
Expect flurries with warmer temperatures and freezing levels around 1900m will for Wednesday before a cooling trend on Thursday. Alpine temperatures should remain below freezing. Winds will be moderate out of the SW.
Snowpack Summary
40 to 80 cm of storm snow with SW winds in the last two weeks has helped create a thick supportive slab over the weak basal facet layer in thin snowpack areas. Rain on Saturday created a surface rain crust to about 2000m which is now frozen and covered by new snow. The valley bottom snowpack is also refrozen after becoming rain saturated.
Avalanche Summary
Natural activity to size 3+ was observed Monday in Yoho and Banff. Both natural and explosive control work today and over the past several days has produced massive results in the Lake Louise and Yoho regions with impressive propagation. Many large avalanches have run to the bottom of their run outs entraining moist snow at lower elevations.
Confidence
Due to the number and quality of field observations
Avalanche Problems
Persistent Slabs
Several buried weak layers in the middle and lower parts of the snowpack have become reactive again as they have been overloaded by recent snow and rain. Large avalanches are reaching historical run outs and crossing valley bottom trails.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
- Be wary of slopes that did not previously avalanche.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 3 - 4
Wind Slabs
Wind slabs over 1m deep exist at higher elevations and at ridge crests near tree line. These slabs are still reactive in tests and could produce avalanches. Cornices have also grown significantly and are fragile. Avoid areas with wind effect.
- If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.
- Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 2 - 3
Loose Wet
With warming temperatures we may start to see loose wet avalanches at lower elevations and on steep solar aspects over the next couple of days. Watch for clues like snowballing that indicate that the snow surface is warming.
- If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.
- Use extra caution on slopes if the snow is moist or wet.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 2