Avalanche Forecast
Issued: Jan 12th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Cornices and Persistent Slabs.
ldreier,
Avalanche Canada
Avalanche conditions remain very dangerous with warm temperatures, recent new snow that formed a dense storm slab and a persistent weak layer in the snowpack.
Summary
Confidence
Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.
Weather Forecast
Wednesday night: Cloudy, up to 5 cm new snow, moderate southwest wind, treeline low around -1 °C, freezing level around 2000 m. Â
Thursday: Mostly sunny, moderate southwest wind, treeline high around +2 °C, freezing level around 2000 m.
Friday: Mix of sun and cloud, up to 3 cm new snow, light westerly wind, treeline high around -2 °C, freezing level around 1200 m.
Saturday: Mostly cloudy, up to 3 cm new snow, moderate southwest wind, treeline high around -2 °C, freezing level around 1400 m.
Avalanche Summary
On Monday and Tuesday, now new avalanches were reported.
On Sunday, a few natural cornice failures resulting in size 2.5 avalanches were observed as well as a natural size 2 slab avalanche.Â
On Saturday, storm slab avalanches up to size 2.5 were triggered by explosives. Overnight, a large (size 3.5) natural storm slab avalanche released and a large (size 2.5) cornice failure occurred.Â
The persistent slab problem has produced sporadic and spotty activity in the Lizard-Flathead and nearby regions.Â
- On Monday, a large size 3 deep persistent slab released naturally in the neighbouring Waterton National Park. The avalanche was more than 2 m deep.
- On Sunday, a very large (size 4) persistent slab avalanche that released naturally in the neighbouring Waterton National Park was observed. The avalanche released at an elevation of 2000 m on an E-NE aspect. Large avalanches (up to size 3.5) were reported in the Fernie area with the early December layer as suspected bedsurface. The avalanches likely ran during the storm on Friday or Saturday.
- Last Wednesday, two size 3 persistent slab avalanches were reported. They released at an elevation of 1800 m and 2000 m on an E aspect and were 2 m deep. Most likely they released during the storm before the New Year.Â
- Last week on Sunday, a size 2.5 persistent slab avalanche was triggered on an E aspect at treeline. This avalanche is detailed in a MIN post and features in our latest blog post, Photos of recent persistent slab avalanches in the southern interior.
Snowpack Summary
The storm brought up to 35 cm of dense, new snow. The new snow sits on soft snow in sheltered areas, wind slabs in exposed and open areas which formed over the past few days. The previous storm snow totalled 40-50 cm and covered a soft, faceted snow surface which formed during cold temperatures. This layer may still take a little time to bond.Â
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 100-270 cm. Activity on this layer has been sporadic, the most recent persistent slab avalanche in the region was reported on January 9. This layer has created a low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
Terrain and Travel
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Storm Slabs
Up to 35 cm new snow fell with warm temperatures building a dense storm slab. Expect to find more reactive deposits around ridge features. Be especially mindful around steep and convex openings in the trees.
The new and recent storm snow may overlie a weak interface which could result in deeper and touchier than expected slabs. Smaller avalanches can step down and trigger deeper weak layers resulting in large and destructive avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are reactive to human traffic with the warm temperatures and natural cornice falls become more likely. Large cornice falls are dangerous on their own.
A failed cornice can trigger buried persistent weak layers and result in very large and destructive avalanches.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A persistent slab problem formed by a crust down 100-270 cm has created a low likelihood, high consequence scenario that is difficult to forecast. There has been an increase of avalanche reports on this layer recently. It is uncertain how the forecast warm temperatures will affect the snowpack and if we will see more activity on this layer during the warm period.
Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack. Large additional loads like small avalanches or cornice falls can trigger deeper weak layers. The same feature or path can slide repeatedly when the persistent weak layer is reloaded with new snow.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 13th, 2022 4:00PM
