Avalanche Forecast

Issued: Feb 4th, 2017 4:15PM

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

Avalanche Canada cgarritty, Avalanche Canada

A bit of new snow in the south of the region has resupplied our wind slab problem. Ongoing wind slab and persistent slab problems remain a concern everywhere else.

Summary

Confidence

Moderate -

Weather Forecast

Saturday night: Scattered flurries bringing approximately 5 cm of new snow. Winds light from the northeast.Sunday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds light from the northeast. Alpine temperatures of -22.Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Winds light from the northeast. Alpine temperatures of -23.Tuesday: A mix of sun and cloud. Winds light from the east. Alpine temperatures of -19.

Avalanche Summary

Recent reports include details of a remote triggered size 2.5 avalanche that occurred in the south of the region on Thursday. The slide took place on a roughly 30 degree south-facing slope at 2100 m in elevation. The remote trigger, a depth of 80 cm, and a failure plane attributed to our January 15 surface hoar all reinforce enduring concerns for persistent slab problems in the region.On Monday, several natural wind slab and storm slab avalanches up to size 2.5 were reported. These slabs were typically 30-50 cm thick and failed on a variety of aspects at treeline and in the alpine. Fresh wind slabs have since been (and are expected to remain) sensitive to light triggers, especially on steep and unsupported (convex) slopes.Persistent slab avalanches remain a serious concern for the region. Last week people triggered numerous large avalanches, several of which resulted in multiple burials. These avalanches all released on, or stepped down to, the mid-December persistent weakness down 1-1.5 m in the snowpack. Check out this list of recent near misses which includes many in the Cariboo region.

Snowpack Summary

Light snowfall over Friday and Saturday (mainly in the south of the region) has given a thin cover to a variety of surface conditions that have developed over the past week. In addition to resupplying the wind slabs that exist on a variety of aspects in wind exposed terrain, the new snow is beginning to cover both faceted surface snow as well as surface hoar that exists on sheltered open slopes. The persistent weakness buried mid-January is now down 50-100 cm and consists of buried surface hoar in sheltered areas, and/or widespread faceted old snow. It has generally stabilized but may remain sensitive to human triggers in isolated areas, especially where buried surface hoar is preserved. Another surface hoar/facet weakness was buried mid-December and can now be found down 70 cm in shallow snowpack areas, or as much as 1.5 m in deeper snowpack areas. It woke up during the last storm and has remained reactive to human triggers. This weak layer is responsible for several large human-triggered avalanches, including some with multiple burials, and the layer may remain reactive for the foreseeable future. Click here for a new blog post with more details.

Problems

Wind Slabs

An icon showing Wind Slabs
Variable winds have formed wind slabs on a wide range of aspects in the days since the storm. Light snowfall and gusty winds over the past couple of days have contributed to the problem, especially in the south of the region.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Avoid areas where the surface snow feels stiff or slabby.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
The persistent weakness buried mid-December has been responsible for several large human-triggered slab avalanches and subsequent burials last week. These deeper weaknesses will be slow to heal and need to be considered in your terrain selection.
Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid shallow snowpack areas where triggering is more likely.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Feb 5th, 2017 2:00PM

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