Avalanche Forecast

Kootenay Boundary

Date issued

Dec 2, 2017 - 3:35 PM

Valid until

Dec 3, 2017 - 2:00 PM

Prepared by

mgrist

The lure of powder slopes and sunny skies will be strong as the weather clears. Take a cautious approach towards more aggressive terrain - especially steep, wind-affected terrain.

Regular season
Sunday - December 3, 2017
Alpine

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.

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.

Below Treeline

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.

Monday - December 4, 2017
Alpine

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.

Treeline

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.

Below Treeline

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.

Tuesday - December 5, 2017
Alpine

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.

Treeline

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.

Below Treeline

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.

Avalanche Problem 1: Storm Slabs

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

Recent wind and snowfall formed storm slabs, which may be more reactive in heavily wind-exposed terrain, or in areas where the new snow has a weak bond with underlying crusts.

Travel and Terrain Advice
  • Be cautious as you transition into wind affected terrain.
  • The new snow may require several days to settle and stabilize.

Avalanche Summary

On Thursday we had a report of a skier-triggered Size 1 storm slab at 2000m on a north west aspect near Nelson. See here for the MIN report. The recent storm snow has been reactive to ski cutting, especially lee features which have seen wind loading.

On Tuesday a naturally-triggered size 1 storm slab was observed around Kootenay Pass. The avalanche occurred on a southeast aspect at about 2100m, and is thought to have failed on the recently buried crust. A natural storm slab avalanche cycle is expected in response to recent wind and snowfall. The possibility of human triggering these storm slabs may continue into the weekend.

We currently have very limited observations in this region. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

30 - 50cm of new snow has fallen in the past week. At higher elevations, south through west winds (gusting strong at times) redistributed the new snow, forming wind slabs on lee features.

Below the recent storm snow you'll likely find a couple of widespread crusts which formed as a result of last week's rain.

Late November's rain really shrunk the snowpack and has transitioned much of the snowpack from dry to moist snow. The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 100-170cm in the alpine, 50-100cm at treeline, and decreasing rapidly below treeline where the primary hazards are rocks, stumps, and open creeks.

We currently have very limited snowpack observations within this region and it is critical to supplement this information with your own observations.

Weather Forecast

We'll see a clearing trend on Sunday afternoon and fine weather during the week.

Sunday: Lingering flurries (10 cm possible over southern sections) and then clearing in the afternoon. Light northwesterly winds. Freezing levels 800m.

Monday: Sunny with cloudy periods. Freezing levels around 600 m. Light northwesterly winds.

Tuesday: Mainly sunny and becoming warm up high. Freezing levels rising to 1500 m. Light northerly winds.

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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