Avalanche Forecast

Issued: Feb 1st, 2017 4:40PM

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

Avalanche Canada cam_c, Avalanche Canada

Fresh storm and wind slabs are likely deeper and more widespread in the norther part of the region. Deeper persistent weaknesses maintain low probability but high consequence conditions.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

THURSDAY: Mainly sunny with light northeasterly winds. Freezing levels in valley bottoms with alpine temperatures reaching -15 C.FRIDAY: Increasing cloudiness with light snow flurries starting in overnight. Light but gusty southwesterly winds and freezing levels remaining in valley bottoms with alpine temperatures reaching -10 C.SATURDAY: Cloudy with light flurries and light but gusty southwesterly winds. Freezing levels remaining in valley bottoms with alpine temperatures reaching -10 C.

Avalanche Summary

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. Skiers also triggered several size 1 slabs. Fresh wind slabs are expected to remain sensitive to human triggering, especially on steep and unsupported (convex) slopes. Winds have recently switched from south to north and wind slabs should be expected on all aspects in exposed terrain.Persistent slab avalanches also remain a serious concern for the region. Last week there were numerous large human triggered avalanches and several of these avalanches involved multiple people being buried. 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

10-60 cm of recent snow (with the largest amounts in northern parts of the region) and strong shifting winds have resulted in fresh wind slabs on a variety of aspects in wind exposed terrain. 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 triggers in isolated areas 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 continue to remain reactive for the foreseeable future. Click here for a new blog post with more details.

Problems

Storm Slabs

An icon showing Storm Slabs
In places the received more than around 30 cm of new snow, storm slabs are expected to be reactive to triggering. In the south of the region, wind slabs are expected to be the primary concern.
The new snow will require several days to settle and stabilize.Use caution in lee areas in the alpine and treeline. Storm snow will form slabs.Avoid areas where the surface snow feels stiff or slabby.

Aspects: All aspects.

Elevations: All elevations.

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 can still be triggered with nasty consequences.
Avoid shallow snowpack areas where triggering is more likely.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Feb 2nd, 2017 2:00PM

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