Avalanche Forecast
Issued: Dec 13th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
bchristie,
Avalanche Canada
Choose smaller features, and avoid slopes that steepen as they descend. Adding a rider's weight to the recent storm snow may start a large avalanche that slides on a hard crust.
Summary
Confidence
Weather Forecast
Some significant snowfall potential overnight. Cloud and intermittent light flurries keep hanging around for the next few days.
MONDAY NIGHT: Overcast. 6-15 cm of snow expected. Light southeast winds at treeline and strong south or southwest in the alpine. Freezing level around 500m.
TUESDAY: Mostly cloudy potential clearing in the afternoon. 0-5 cm of snow expected. Light to moderate southwest winds. Freezing level rising to around 750m.
WEDNESDAY: Partly cloudy. 0-2 cm. Light to moderate southwest winds, up to strong on higher peaks. Warming through the day, alpine high around -10.
THURSDAY: Brief clearing overnight, partly cloudy through the day. Possible trace of snow. Light to moderate southwest winds, with strong to extreme westerlies on higher peaks. Alpine high around -8,
Avalanche Summary
This MIN Report paints a good picture of the avalanche problem right now. They spotted a natural avalanche in a wind loaded feature, and whumpfing in shallow areas.
Reports indicated that the snowpack was quite touchy this weekend. Avalanche control with explosives and ski cuts produced several size 2 avalanches, and one size 3. Most failed on top of the rain crust from the late November/early December rain events.
Snowpack Summary
A refresh of snow overnight keeps the snowpack in a state of change. Mostly light winds are forecast through the storm, so the new snow should be relatively unconsolidated. Where this new snow has been wind transported, (most likely at higher elevations) it could form reactive slabs.
Moderate to strong southwest winds during the last storm formed wind slabs that are still taking time to bond to the rest of the snowpack. These slabs are now buried by the new snow. While that makes them harder to find, it does not mean they are less likely to avalanche.
Most of the recent avalanche observations have run on the early December rain crust. We suspect that weak, facetted snow has begun to form on top of the crust.
Snowpack depths are extremely variable due to strong to extreme southwest winds from early December that stripped snow off of exposed areas, and made deep drifts in lee slopes.
Below 2300m, several early season crusts are breaking down and forming a cohesive lower snowpack.
Snowpack depths range from 50-110 cm at treeline elevations. The snowpack tapers quickly below 1900m.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Choose simple, low-angle, well supported terrain without convexities.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
Southwest of Pincher Creek, avalanche control has produced explosive and skier triggered avalanches on this layer.
This crust is widespread across the province, and many operations have been watching it for signs of reactivity as the load on top of it increases. It may also get more reactive as cold temperatures promote faceting above the crust.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Moderate to strong southwest winds have formed the recent storm snow into slabs that are deeper and more reactive in leeward features.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 14th, 2021 4:00PM
