Avalanche Forecast

Issued: Jan 28th, 2018 4:36PM

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

Avalanche Canada mbender, Avalanche Canada

With several buried weak layers and a rising freezing level on Monday, the snowpack is primed for human triggering. A conservative approach to terrain selection is recommended.

Summary

Confidence

Moderate - Freezing levels are uncertain on Monday

Weather Forecast

MONDAY: Cloudy with flurries, accumulation 5-10cm / Strong southwest wind / Alpine temperature -2 / Freezing level 1800mTUESDAY: Flurries, accumulation 5cm / Strong west wind / Alpine temperature -4WEDNESDAY: Mix of sun and cloud / Light west wind / Alpine temperature -10

Avalanche Summary

On Thursday explosive control work in the Castle area triggered a Size 3 avalanche from a shallow area that propagated and failed on the late-November layer deep in the snowpack. While in the Bull River area a natural Size 1.5 wind slab avalanche was observed on a northwest aspect at treeline and a natural Size 2 in a west-facing cutblock at 1600 m was reported to have failed on the mid-December layer.The snowpack in the region remains suspect with several buried weak layers displaying classic signs of instability such as whumpfing and cracking. The recent video posted to the Avalanche Canada South Rockies field team Facebook page paints a pretty clear picture. https://www.facebook.com/avcansouthrockies/videos/1894352117306941/.

Snowpack Summary

Amounts vary across the region however, about 20-50 cm of recent storm snow now covers both a new layer of feathery surface hoar in sheltered areas as well as sun crust on solar aspects buried mid-January, and about 30-60 cm below the surfaces lies the early-January surface hoar layer.About 60-80 cm below the surface a weak layer of feathery surface hoar crystals and/or sun crust buried mid-December is found at treeline and below treeline elevations. Near the base of the snowpack the weak early-season layer of rain crust and sugary facets buried late-November exists. Although the snowpack structure is variable across the region, these persistent weak layers are generally widespread. Snowpack depths are also variable across the region and typically thinner in northern areas than in areas to the south.

Problems

Wind Slabs

An icon showing Wind Slabs
New snow and wind this week have created wind slabs in leeward areas near ridge crest in the alpine and in exposed treeline areas. These slabs are touchy and have been reactive to natural triggers in recent days.
If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Several weak layers of concern are buried within the snowpack and have the potential to produce large avalanches. Conservative terrain with moderate-angled, supported slopes are good choices.
Be aware of thin snowpack areas where deeper weak layers may be more sensitive to triggering.Watch for signs of instability such as whumpfing, or shooting cracks.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Jan 29th, 2018 2:00PM