Avalanche Forecast
Issued: Dec 19th, 2020 4:00PM
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.
Aaron Beardmore,
More snow and wind arriving Saturday night. Wind slabs in alpine start zones and gullies have the capacity to entrain facets and run to valley bottom. Know what is above you on Sunday.
Summary
Weather Forecast
More snow is on the way, Saturday night, amounting to about 20cm by Sunday morning. Up to 45cm by end of day Tuesday. The wind is also to remain strong from the W -SWÂ through Saturday night, facilitating transport. Temperatures will remain seasonal at -5 in the valley and -15 at the ridge.
Snowpack Summary
Cornices growing and 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 at treeline is between 80-160 cm.
Avalanche Summary
Very little avalanche activity was reported by Lake Louise ski patrollers today. Little activity was noted by the forecasting team up 93N today also. Conversely, patrollers at Sunshine were able to ski cut wind slabs at tree line and above up to size 1.5. They also observed a size 2-2.5 come of Bourgeau Left, a wind slab that entrained facets.
Confidence
Timing, track, or intensity of incoming weather system is uncertain on Sunday
Problems
Wind Slabs
Widespread wind slabs are expected in the alpine and down into treeline with arrival of strong winds and new snow . In steep avalanche paths and gullies these have the potential to run down below treeline entraining facets.
- 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
The strong winds and new snow will likely cause loose dry avalanches in steep gullies and on steep faces. These avalanches will be smaller but could run a long ways in the recent storm snow.
- 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 limited 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 20th, 2020 4:00PM
