Avalanche Forecast

Issued: Dec 28th, 2016 3:56PM

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

jfloyer, Avalanche Canada

Northwest Inland.

Hard wind slab over weak, sugary facets should be treated with respect - it has the right structure to support a large, dangerous avalanche.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

THURSDAY: Light snow, 4-8 cm. Winds 20-30 km/h from the east. Alpine temperatures around -10C. FRIDAY: Dry with some sunny breaks. Northwest winds increasing through the day to 60 km/h by the afternoon. Temperatures around -15C. SATURDAY: Flurries. Strong northerly winds. 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

Moderate to strong winds continue to redistribute the 10-30 cm of low density storm snow, forming touchy wind slabs in the lee of exposed ridges. The new snow has also buried a layer of feathery surface hoar (up to 15 mm in sheltered areas), making wide propagations possible. There is another weak layer that formed during the early December cold snap which is now about 40-60 cm deep. However, the layer that was responsible for most of the large avalanches during the big storm just before Christmas was the mid-November rain crust. This lies close to the bottom of the snowpack and is associated with sugary facets. Because of the low snow depths (around 1 m), this layer remains very much a concern in this region.

Problems

Wind Slabs

Expect fresh wind slabs as strong westerly winds redistribute the new snow. Wind slabs may also be burying a layer of surface hoar that could make them extra touchy.

Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.Avoid freshly wind loaded features.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

40-60 cm of recent snow sits above a weak, faceted lower snowpack. While not super deep, the facets in the lower half of the snowpack have lingered for a long time now. Likely trigger points are unsupported slopes in shallower snowpack areas.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Dec 29th, 2016 2:00PM