Avalanche Forecast
Issued: Mar 20th, 2017 4:00PM
The alpine rating is Persistent Slabs, Wind Slabs and Loose Wet.
, the treeline rating is , and the below treeline rating is Known problems includeNatural activity is still occurring and the potential for very large human triggered avalanches on the buried facets remains high. Avoid exposure to overhead hazard and stick to moderate angled supported terrain to enjoy the new snow.
Summary
Weather Forecast
The ridge will break down on Tuesday as clouds and flurries with warmer temperatures push into the region in the afternoon. Flurries with warmer temperatures and freezing levels around 1850m will continue for Wednesday before a cooling trend returns. 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 again today in Yoho and Banff. Both natural and explosive control work in the last 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
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.
- Be wary of slopes that did not previously avalanche.
- Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
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.
- Pay attention to overhead hazards like cornices which could easily trigger persistent slabs.
- If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.
Aspects: North, North East, East, South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
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.
- Use extra caution on slopes if the snow is moist or wet.
- If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Mar 21st, 2017 4:00PM