Avalanche Forecast
Issued: Dec 17th, 2020 5:18PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Loose Dry and Deep Persistent Slabs.
Conrad Janzen,
We have elevated the hazard at all elevations based on strong winds and incoming snow on Friday afternoon, and the potential for avalanches triggered at upper elevations to run full path in steep areas. Minimize overhead hazard for the next few days!
Summary
Weather Forecast
Strong winds and heavy snowfall are forecast starting Friday afternoon with some forecasts suggesting 15-20 cm by Saturday morning on the 93 N. Less snow is expected Eastern and Southern areas but winds will still be strong. Valley bottom temperatures should stay around -5 with ridge top temperatures around -12 to -15.
Snowpack Summary
Wind slabs forming in the alpine with moderate to strong W winds. 20-50 cm of storm snow at treeline sits over the Dec 13 and Dec 7 layers of sun crust, facets and some surface hoar. The Nov crust/facets exist near the bottom of the snowpack and are weakest in shallow snowpack areas. Snowpack depths at treeline are between 80-160 cm.
Avalanche Summary
Ski resorts reported small ski-cut and explosive triggered wind slabs and loose dry avalanches up to size 1.5 on Thursday. Weather limited visibility in the alpine and no other natural avalanches were observed or reported.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Friday
Problems
Wind Slabs
Wind slabs are expected to form at treeline and in the alpine on Friday as the winds increase and more snow arrives. There is a fair bit of potential for these to start failing naturally and even running down into lower elevations in steep terrain.
- Choose ice climbs that are not exposed to avalanches from above.
- Minimize overhead exposure during periods of heavy loading from wind.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
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: 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. We have isolated observations of deep slab avalanches recently but increasing wind and snow over the next three days may change this.
- 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 18th, 2020 4:00PM
