Archived

Avalanche Forecast

Dec 29th, 2016–Dec 30th, 2016

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Inland.

Cold, northwesterly winds mark a change in wind direction, which will set up fresh wind slabs in new locations in exposed terrain.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

FRIDAY: Dry, with some clear spells, but strong northwest winds blowing up to 60 km/h at ridgetop. Temperatures around -15C. SATURDAY: Light snow 3-5 cm with continued strong northwesterly winds 60-80 km/h at ridgetop. Temperatures around -9C. SUNDAY: Dry with clear spells. Continued strong winds from the north. Temperatures around -10C.

Avalanche Summary

No avalanches have been reported since Monday, when, a skier remote triggered a size 1.5 wind slab in the Hankin area on a north aspect at treeline (see MIN report). Wind slabs will remain touchy throughout the week, as sustained winds will redistribute the new low density snow. The additional load of new snow will also keep deeper persistent weak layers reactive, making it possible to trigger larger avalanches.

Snowpack Summary

Snowpack depths in this region are still shallow - around 1 m or so, meaning there are a lot of weak sugary facets in the snowpack at this time. Recent storm snow has been redistributed by the wind, and wind slabs are widespread behind exposed ridges. Where hard wind slabs overlie weak facets, the structure is ripe for human-triggered avalanches. In addition to the sugary facets, you may find a layer of feathery surface hoar (up to 15 mm in sheltered areas), buried around 15-25 cm below the surface. There is another weak layer that formed during the early December cold snap which is now about 40-60 cm deep. A crust from mid-November may be found close to the bottom of the snowpack nestled in amongst the facets. We don't have a lot of information about these layers, but it's worth noting the layer responsible for most of the large avalanches during the big storm just before Christmas was the mid-November rain crust.

Avalanche Problems

Wind Slabs

After a calmer day on Thursday, winds are expected to increase again, this time from the northwest. Watch for areas that were previously scoured and may become reverse-loaded as the winds switch direction.

Be cautious as you transition into wind affected terrain.Avoid freshly wind loaded features.Avoid travelling in areas that have been reverse loaded by winds.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Deep Persistent Slabs

40-60 cm of recent snow sits above a weak, faceted lower snowpack. This fundamentally weak snowpack structure supports human-triggered avalanches from places like convex slopes in shallow areas, and is likely to persist for some time.

Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3