Avalanche Forecast

Issued: Dec 27th, 2016 3:49PM

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

shorton, Avalanche Canada

Northwest Inland.

Tricky snowpack conditions exist and require a conservative and cautious approach to terrain, especially if you see signs of recent loading.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

WEDNESDAY: Flurries with accumulations up to 10 cm, 40-60 km/h southwest winds, temperatures around -8C.THURSDAY: Flurries with 5-10 cm accumulations, 20-40 km/h northwest winds, temperatures around -8C.FRIDAY: Cloudy with isolated flurries, 60-80 km/h northwest winds, temperatures around -10C.

Avalanche Summary

On Monday, a skier remote triggered a size 1.5 wind slab in the Hankin area on a north aspect at treeline (see MIN report). They also reported a whumpfing caused by collapsing facets at the bottom of the snowpack. Over the weekend, numerous size 1.5-2 avalanches were remote triggered in the northern parts of the region, also releasing on weak facets near the ground.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 are redistributing 10-30 cm of low density storm snow and 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. A weak interface that formed during the early December cold snap can be found about 40-60 cm deep underneath a hard wind slab. The layer consists of weak faceted (sugary) snow, and preserved surface hoar in sheltered areas. The snowpack is still shallow throughout the region and widespread faceting of the lower snowpack is likely in most areas. A thick rain crust that formed in early November is probably near the bottom of the snowpack and is likely surrounded by sugary facets. Basal facets and depth hoar (more sugary crystals) right at the bottom of the snowpack are reportedly widespread.

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.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

40-60 cm of recent snow sits above a weak, faceted lower snowpack. Triggering persistent slabs will become more likely with loading from new snow and wind. Likely trigger points are unsupported slopes in shallower snowpack areas.

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

Valid until: Dec 28th, 2016 2:00PM