Avalanche Forecast

Cariboos

Date issued

Jan 30, 2018 - 4:56 PM

Valid until

Jan 31, 2018 - 2:00 PM

Prepared by

mgrist

Conditions remain primed for human-triggered avalanches. Give the snowpack time to settle before pushing into more aggressive terrain: Simple terrain is recommended for now.

Regular season
Tuesday - January 30, 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 31, 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

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.

Thursday - February 1, 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

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.

Avalanche Problem 1: Storm Slabs

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

Warming temperatures put heavier snow on top of lighter dry snow - a recipe for an unstable snowpack. A storm slab could step down to a deeper weak layer, creating a surprisingly large avalanche.

Travel and Terrain Advice
  • The new snow will require several days to settle and stabilize.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Be wary of slopes that did not previously avalanche.

Avalanche Problem 2: Persistent Slabs

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

Several weak layers are buried in the snowpack, creating very large avalanches when triggered.

Travel and Terrain Advice
  • Avoid steep convexities or areas with a thin or variable snowpack.
  • Make conservative terrain choices, remembering that avalanches may be surprisingly large.

Avalanche Summary

On Tuesday we received preliminary reports of an avalanche involvement in the north Columbia region near Clemina creek. The avalanche ran on a north facing aspect near 1900m.

A natural storm slab avalanche cycle occurred on Monday with heavy snow and temperatures up to +2 Celsius in some tree line locations. See this MIN report for a good example of the avalanche activity.

Conditions remain primed for human triggered avalanches, with the potential for some surprisingly large avalanches given how many persistent weak layers exist in the snowpack.

Snowpack Summary

25-40 cm of storm snow fell from Sunday through to Tuesday and temperatures spiked to -2 at tree line in the south of the region (and +2 near Barkerville) on Monday afternoon. The new snow sits on a complex snowpack and there are three active weak layers we are monitoring:

1) Down about 40-80 cm is a crust and/or surface hoar layer buried mid-January. The surface hoar is up to 10 mm in size, found at all elevation bands and very reactive on north east aspects between 1900-2600m.

2) Deeper in the snowpack, the early-January persistent weak layer is found 50 to 100 cm below the surface.

3) Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 150 cm deep. It has been most problematic at and below tree line.

See here for a good summary of snowpack test results.

Weather Forecast

Wednesday: Cloudy with isolated flurries. Light westerly winds. Alpine temperature near -9.

Thursday: Scattered flurries (5-10cm possible). Light to moderate south-westerly winds. Alpine temperature near -8.

Friday: Snow (10-20 cm). Moderate southerly winds. Alpine temperature -8.

More information can be found in the Mountain Weather Forecast.

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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