Avalanche Forecast

Issued: Feb 14th, 2017 3:40PM

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

rbuhler, Avalanche Canada

South Columbia.

Tricky conditions are expected on Wednesday with warm temperatures continuing, strong winds in the alpine, and new snow/rain. Use a conservative approach and avoid avalanche terrain during periods of rainfall.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A warm storm system reaches the interior on Wednesday morning. 5-10 mm of precipitation is expected during the day on Wednesday with freezing levels around 2500 m in the morning falling to 2000 m in the afternoon. Alpine wind is forecast to be moderate to strong from the southwest. Another 10-20 mm of precipitation is forecast for Wednesday overnight through Thursday afternoon. Freezing levels are forecast to remain around 2000 m on Thursday and alpine wind is forecast to remain moderate to strong from the southwest. Light precipitation is currently forecast to continue Thursday overnight and taper off Friday morning. Friday is forecast to be mostly dry and sunny with freezing levels falling to around 1500 m.

Avalanche Summary

On Monday, natural loose wet avalanches up to size 2 were reported throughout the region from steep sun exposed slopes. A natural size 3 was reported on a northeast aspect at 2500 m and a natural cornice release triggered a size 2 slab on a southeast aspect at 2500 m. A skier also remotely triggered a size 1.5 wind slab on an east aspect at 2400 m which was triggered from 20 m away. On Sunday, a few natural wind slabs were observed in the alpine. A MIN report describes a remotely triggered size 3 avalanche on London Ridge. Click here for more details. On Wednesday, rain at lower elevations is expected to destabilize the upper snowpack resulting loose wet sluffing and potentially increasing the sensitivity of triggering persistent slab avalanches. In the alpine, new snow and strong southwest winds will likely form touchy new wind slabs. Wind slab avalanches have the potential to step down and trigger persistent slab avalanches.

Snowpack Summary

The storm snow from last week has settled rapidly due to the recent mild temperatures. The snow surface is expected to have undergoing melting on Tuesday afternoon on sun exposed slopes. Recent strong winds from the south and west had redistributed the recent storm snow in exposed terrain forming wind slabs. The early February weak layer is typically down 50-80 cm and includes a sun crust on steep sun-exposed slopes, faceted snow, as well as surface hoar on sheltered open slopes. This layer has remained reactive recently and has been the main sliding layer for most of the recent slab avalanche activity. The mid and lower snowpack are generally well settled and stable in deeper snowpack areas but may be faceted and weaker in shallower areas.

Problems

Persistent Slabs

A weak layer from early February down 50-80 cm remains reactive to human triggering in isolated areas. Smaller avalanches have the potential to step down to this layer.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.Be aware of the potential for large avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Wind Slabs

Strong southwest winds, mild temperatures, and new snowfall are expected to form touchy new wind slabs on Wednesday at higher elevations.

Avoid freshly wind loaded features.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, South.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Loose Wet

At lower elevations where the new precipitation falls as rain, expect sluffing from steep terrain features. Sluffs have the potential to trigger slabs on the slopes below.

If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.Use extra caution on slopes if the snow is moist or wet.Avoid avalanche terrain during periods of rain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 15th, 2017 2:00PM