Avalanche Forecast
Regions: Little Yoho.
Strong winds are building slabs in the alpine while warm temperatures and poor overnight recoveries are causing the strength of the snowpack to deteriorate BTL.
As snow and rain are added to the mix Sunday evening, a natural avalanche cycle can be expected to begin.
Confidence
Moderate
Avalanche Summary
Sunshine Village saw a sz 1.5 cornice failure while Lake Louise worked with small wind slabs in the immediate lees and reported a small wind - generated avalanche off of the cliffs on Mt Redoubt.
Snowpack Summary
Up to 5cm of new snow sits over sun crusts on solar aspects. Isolated small wind slabs can be found in the alpine.
A weak, isothermal snowpack is developing BTL with minimal overnight recovery.
Several buried crusts can be found in the top 40cm on solar aspects.
The November depth hoar at the base of the snowpack remains a concern mainly in shallow areas of the Yoho sub-region.
Weather Summary
Freezing levels ~ 1700m overnight Saturday with flurries / showers.
Strong SW winds increase Sunday as freezing levels rise to 2400m.
Winds peak near extreme values overnight Sunday. Freezing level: 2000m with 5 to 10 cm of snow / rain.
Freezing levels higher Monday with 15-30cm of snow / rain. SW winds increase to extreme values.
Terrain and Travel Advice
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Be aware that wet activity at low elevations is a classic situation for step-down failures in deeply buried persistent weak layers.
Avalanche Problems
Deep Persistent Slabs
The November basal facets at the base of the snowpack have mainly been a concern for triggering in shallow snowpack areas of this sub region however with the weather inputs on track for Sunday the potential for these slabs to be triggered increases.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 2 - 3.5
Wind Slabs
Fresh small slabs have formed over the last two days and will continue to develop through the weekend as SW winds peak near extreme values Sunday evening. As these start to fail naturally, consider them to be potential triggers for larger avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Likely
Expected Size: 1 - 2
Loose Wet
With continued poor overnight recoveries, the thin snowpack at the lowest elevations has already gone isothermal losing its strength and structure. With increasing freezing levels and rain in the forecast Sunday, expect this to progress further.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood: Possible - Likely
Expected Size: 1 - 2