Avalanche Forecast
Issued: Dec 16th, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Dry, Wind Slabs and Deep Persistent Slabs.
Stephen Holeczi,
We are at a tipping point as far as avalanche danger, and if there is wind in your area Thursday, avalanche activity will increase. Factor this into the terrain you decide to expose yourself to. Really good ski quality for this time of year.
Summary
Weather Forecast
Continued light snow Thursday (5-10cm) accompanied by moderate to strong south-westerly winds in the alpine. Valley bottom temperatures around -5 and ridge-top temperatures around -12 to -15. Continued winds increasing to extreme into the weekend including 20-40cm expected in some areas by the end of Sunday.
Snowpack Summary
The dominant issue in the snowpack is the 20-30 cm of low density storm snow and 20-25 cm of loose facets overtop of the Dec 7th layer of sun crust, facets or surface hoar. Continued winds are continuing to create fresh wind slabs in open terrain. The Nov 5 facets and crust near the base of the snowpack are less pronounced in this area.
Avalanche Summary
Lake Louise and Sunshine ski resorts report small ski-cut and explosive triggered wind slab and loose dry avalanches up to size 1.5. Some reports of alpine natural avalanches up to size 2.5 in the last 24 hours. A mix of wind slabs and loose dry avalanches likely triggered anytime the winds picked up.
Confidence
Problems
Loose Dry
Up to 40 cm of low density and facetted surface snow is sluffing easily out of steep terrain wherever it is touched by wind. These avalanches are relatively small but running far and picking up mass as they go.
- Be careful of loose dry power sluffing in steep terrain.
- Be cautious with gully features.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
So far wind slabs have been noted in the alpine, but may extend down into treeline wherever the wind has gotten to the new snow. Expect these to grow in size and reactivity in the coming few days.
- Use caution in lee areas. Recent wind loading have created wind slabs.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The Nov 5 crust has facets above and below it, and exists up to 2500m on shady aspects and higher on solar aspects. This layer seems less prevalent in Little Yoho, and there is some uncertainty as to whether it is a problem in this region.
- Be aware of thin areas that may propogate to deeper instabilites.
- Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 17th, 2020 4:00PM
