Avalanche Forecast

Issued: Dec 16th, 2018 4:47PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Persistent Slabs and Wind Slabs.

shorton, Avalanche Canada

Lizard-Flathead.

The potential to trigger large persistent slab avalanches warrants conservative terrain choices.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

SUNDAY NIGHT: A weak front passes overnight bringing 3-10 cm of snow, strong wind from the southwest, alpine temperatures around -2 C.MONDAY: Flurries easing off by the morning before the next storm arrives in the evening, moderate wind from the southwest with strong gusts, freezing level around 1400 m, alpine high temperatures around -1 C.TUESDAY: 15-30 cm of snow, strong wind from the southwest, freezing level around 1500 m, alpine temperatures possible reaching 0 C.WEDNESDAY: Another 5-10 cm of snow, strong wind from the southwest, freezing level dropping to 1300 m, alpine temperatures around -3 C.

Avalanche Summary

On Saturday, a group of skiers remotely triggered a large (size 2) avalanche on a northeast facing slope at treeline in the Corbin area. The skiers were in dense trees and the avalanche released roughly 60 m above them. One skier was fully buried and the group successfully extricated them without significant injuries. For full MIN incident report follow this link.Some recent large (size 2-3) natural avalanches were also reported at treeline elevations in the Harvey area. Most of them were 30-40 cm deep storm slabs, but a few appeared to step down to deeper crust layers. See photos in this MIN report. Smaller wind slabs (size 1) were occurring naturally and reactive to skiers throughout the region on Saturday.

Snowpack Summary

Strong wind has affected most open terrain and formed fresh wind slabs at higher elevations.Roughly 30-50 cm of recent storm snow sits above a weak layer composed of large surface hoar, facets, and/or sun crust. There have been numerous signs of the new snow bonding poorly to this layer including remote triggering from low angle terrain, shooting cracks, and wide propagations in avalanches.Several other weak layers have been observed in the lower snowpack such as early season crusts with weak facets. The most concerning crust is prevalent at higher elevations and is likely most problematic on north-facing features, especially those that are large and planar in nature.

Problems

Persistent Slabs

30-50 cm of recent storm snow sits above a touchy weak layer. Any steep or convex terrain is suspect, especially slopes that have been loaded by the wind.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Stick to simple terrain and be aware of what is above you at all times.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 2.5

Wind Slabs

Strong alpine winds have formed fresh slabs that have the potential to step down to the persistent weak layer.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 1.5

Valid until: Dec 17th, 2018 2:00PM