Avalanche Forecast

Issued: Feb 14th, 2017 4:45PM

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.

Avalanche Canada rbuhler, Avalanche Canada

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. 2-4 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 5-10 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 1.5 were reported from steep sun exposed slopes. Ski cutting triggered a size 1 wind slab on a north aspect at 2200 m. Explosives triggered a couple cornices and several size 2-3.5 slabs. A few of these appear to have released on old weak layers down 120-150 cm in the snowpack. On Sunday, a few natural size 1.5-2.5 wind slabs were observed. One of the wind slabs stepped down to a deeper layer. A ski cut on a northeast aspect at 1300 m elevation triggered a size 1.5 deep persistent slab which failed on an old layer near the ground. Explosives triggered numerous storm slabs up to size 2.5 as well as two deep persistent slabs up to size 3.5 which released down 200 cm, most likely on the November crust. 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 60-80 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. A persistent weakness buried mid January is now down 80-150 cm and the November crust is down around 200 cm. These deep persistent weaknesses appear to be waking up with the warmer temperatures and several avalanches have recently released up to 2 m deep.

Problems

Persistent Slabs

An icon showing Persistent Slabs
A weak layer from early February down 60-80 cm remains reactive to human triggering in isolated areas. Deeper weak layers in the snowpack appear to have woken up this week and very large avalanches are possible in isolated areas.
Be aware of the potential for large avalanches due to the presence of deeply 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

3 - 4

Wind Slabs

An icon showing 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.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

An icon showing 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

Expected Size

1 - 2

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