Avalanche Forecast

Issued: Feb 14th, 2017 4:18PM

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

rbuhler, Avalanche Canada

Cariboos.

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

Low - Due to the number of field observations

Weather Forecast

A warm storm system reaches the interior on Wednesday morning. Around 5 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 5-15 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 partly sunny with freezing levels falling to around 1500 m.

Avalanche Summary

On Monday, natural loose wet avalanches up to size 2 were reported from steep sun exposed slopes. A skier triggered a size 1.5 storm slab on a southwest aspect at 2000 m. On Sunday, four solar triggered size 2 storm slab avalanches were observed on southeast and south aspects at 1400-2200 m. Ski cutting produced two size 1 storm slab avalanches on southeast aspect at 1850 m. Over the weekend, several rider triggered avalanches were reported on the MIN including a size 3 that resulted in a full burial. Click here more details (1). (2), and (3). 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 settling 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 40-70 cm and includes hard old wind slabs, 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 persistent weakness buried mid-January is now down around 80-100 cm and the surface hoar/facet weakness buried mid-December is down 100-150 cm. These deep persistent weaknesses have the potential to wake up and become reactive with the current warm temperatures.

Problems

Persistent Slabs

A weak layer from early February down 40-70 cm remains reactive to human triggering in isolated areas. Deeper weak layers in the snowpack also have the potential to wake up this week and very large avalanches are possible in isolated areas.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Wind Slabs

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

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

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.

Use extra caution on slopes if the snow is moist or wet.If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.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