Avalanche Forecast

Cariboos

Date issued

Jan 8, 2018 - 5:03 PM

Valid until

Jan 9, 2018 - 2:00 PM

Prepared by

mconlan

New snow is falling on numerous weak layers and will likely be reactive to natural and human triggers. Storm slabs have the potential to step down and trigger deeper persistent weak layers. Conservative terrain choices are recommended.

Regular season
Monday - January 8, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Tuesday - January 9, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Wednesday - January 10, 2018
Alpine

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Below Treeline

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation,cautious route-finding and conservative decision-making essential.

Natural avalanches possible;human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

Avalanche Problem 1: Storm Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Around 20 to 40 cm of new snow, with the highest amounts in the south of the region, is sitting on variable surfaces and may not bond well to them. The snow could be deeper in northwesterly lee features due to strong winds.

Travel and Terrain Advice
  • If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.
  • Avoid exposure to terrain traps where the consequence of a small avalanche could be serious.
  • Use caution when entering lee areas. Recent wind loading may have created wind slabs.

Avalanche Problem 2: Persistent Slabs

What Elevation?
Which Slopes?
Chances of Avalanches?
Expected Size?

Around 40 to 70 cm of snow sits above a touchy weak layer. As this snow continues to settle and gains slab properties, a dangerous slab that is easily triggered may form. Shallower storm slabs could step down to this layer.

Travel and Terrain Advice
  • Use conservative route selection. Choose moderate-angled and well-supported terrain.
  • Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Avalanche Summary

Storm slab avalanches were reported on Saturday, being triggered naturally and by skier activity. The slabs were small to large (size 1 to 2) and generally observed around treeline and alpine terrain with depths of about 20 cm. One release occurred in a loaded lee slope near ridgetop.

Please share your observations through the Mountain Information Network.

Snowpack Summary

20-40 cm of new snow fell on surface hoar in sheltered slopes and a sun crust on steep solar aspects and may not bond well to them. The snow also fell with moderate southwesterly winds in the alpine, which likely produced small wind slabs in lee features.

The new snow could create a dangerous slab above buried weak layers. Numerous persistent weak layers exist deeper in the snowpack. Dry snow overlies three layers composed of weak and feathery surface hoar, with the deepest layer (December 15) buried 40 to 70 cm. This layer is shallower in the north of the region and deeper in the south of the region. The weak layer is found most often at treeline and below treeline. As the snow above the weak layers becomes more cohesive and forms a slab, the setup has the potential to create easily-triggerable destructive slab avalanches. Snowpack test results in this MIN post show that this layer could be reactive.

Deeper in the snowpack at depths of about 70 to 100 cm, a rain crust from November is producing variable snowpack test results, from sudden fracture characters to no result. This layer is considered dormant but could be triggered where the snowpack is thin.

Weather Forecast

TUESDAY: Cloudy with light flurries, accumulation 5-10 cm, light to moderate westerly winds, alpine temperature dropping to -10 C over the day, freezing level below valley bottom.

WEDNESDAY: Partly cloudy with intermittent flurries, light to moderate southwesterly winds, alpine temperature near -14 C, freezing level below valley bottom.

THURSDAY: Partly cloudy with intermittent flurries, light westerly winds, alpine temperature near -10 C, freezing level below valley bottom.

Danger Ratings Explained

1 - Low

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Natural and human-triggered avalanches unlikely.

Small avalanches in isolated areas or extreme terrain.

2 - Moderate

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Natural avalanches unlikely; human-triggered avalanches possible.

Small avalanches in specific areas; or large avalanches in isolated areas.

3 - Considerable

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Natural avalanches possible; human-triggered avalanches likely.

Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.

4 - High

Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.

Natural avalanches likely; human-triggered avalanches very likely.

Large avalanches in many areas; or very large avalanches in specific areas.

5 - Extreme

Avoid all avalanche terrain.

Natural and human-triggered avalanches certain.

Large to very large avalanches in many areas.

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