Avalanche Forecast
Regions: Lizard-Flathead.
Touchy new storm slabs are expected to form on Monday, especially in wind loaded terrain. The region continues to deal with a persistent slab problem and very large avalanches remain possible. Conservative terrain selection remains critical.
Confidence
High - We are confident a natural avalanche cycle will begin shortly after the arrival of the incoming weather.
Weather Forecast
A storm system is forecast to bring substantial snowfall to the region on Sunday night and Monday with strong winds.Â
Sunday night: Snowfall 10-15 cm, moderate to strong SW wind, treeline temperature around -12 °C.Â
Monday: Snowfall 15-30 cm, moderate to strong SW wind, treeline high around -10 °C.Â
Tuesday: Unsettled conditions with snow flurries and sunny breaks, light to moderate SW wind, treeline high around -10 °C.Â
Wednesday: A mix of sun and cloud, light to moderate NW wind, treeline high around -16 °C.Â
Avalanche Summary
No new avalanches were reported on Saturday. On Friday, a size 2.5 persistent slab avalanche was reported on a north aspect at 2000 m elevation. This failed on the early December weak layer down 100-175 cm. Also on Friday, explosives were triggering wind slabs up to size 1.5. Last week, a few surprisingly deep older crowns were observed between Fernie and Sparwood. These persistent slab avalanches likely ran on the early December crust.Â
On Monday, new storm slabs are expected to form with the incoming storm system and strong winds. These new slabs will sit on a weak snow surface and may be very reactive, especially in wind loaded terrain. The persistent slab problem remains a serious concern and the weight of the new snow may increase the reactivity of these deeper layers. Smaller storm slab avalanches also have the potential to step down to deeper layers resulting in very large avalanches.Â
Snowpack Summary
The new storm snow buries a highly wind affected snow surface and widespread facets from the recent cold conditions which is expected to create a weak bond with the new snow. The new snowfall is expected to be accompanied by strong winds and reactive new slabs are expected to be widespread.Â
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 80-150 cm. Activity on this layer has been sporadic, but most recently produced a large avalanche on December 31. 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
- Storm slab size and sensitivity to triggering will likely increase through the day.
- 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.
Avalanche Problems
Storm Slabs
Storm slabs are expected to form on Monday with new snowfall and strong SW wind. These slabs will overlie a weak snow surface and may become touchy right away, especially in wind loaded areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Likely - Very Likely
Expected Size: 1 - 2.5
Persistent Slabs
A persistent slab problem formed by a crust down 50-150 cm has created a low likelihood, high consequence scenario that is difficult to forecast. Avoid likely trigger spots such as steep, rocky slopes with a shallow or thin to thick snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely - Possible
Expected Size: 2 - 3.5