Avalanche Forecast

Kootenay Boundary

Date issued

Jan 23, 2018 - 4:43 PM

Valid until

Jan 24, 2018 - 2:00 PM

Prepared by

jsmith

Avalanche hazard is forecast to increase throughout the day on Wednesday. Avoid all avalanche terrain during periods of rapid loading from snow or wind.

Regular season
Tuesday - January 23, 2018
Alpine

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.

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 24, 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 - January 25, 2018
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

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?

Forecast new snow, wind, and warming are expected to create very touchy storm slabs during the day on Wednesday. If triggered, these slabs have the potential to step down to one or more deeper weak layers buried in the snowpack.

Travel and Terrain Advice
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Be cautious when transitioning into wind effected terrain.

Avalanche Problem 2: Persistent Slabs

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

The snowpack is complex and has produced very large and destructive avalanches on up to four separate weak layers buried 50 to 140cm below the surface. A conservative approach and moderate-angled, simple terrain are good choices.

Travel and Terrain Advice
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.

Avalanche Summary

On Monday, numerous explosive triggered, size 2 storm slab avalanches were reported near Whitewater and Kootenay Pass. Looking forward, forecast snow and wind will promote ongoing storm slab avalanche activity, especially in higher elevation, lee terrain.

Snowpack Summary

Since last Friday, 15-30cm of new snow fell with the greatest accumulations occurring in the Kootenay Pass area. Moderate to locally strong southwest winds have redistributed the new snow into reactive storm slabs in exposed lee terrain.

Approximately 30 - 50 cm of storm snow now covers the most recent crust/surface hoar layer that was buried mid-January. This crust can be found on solar aspects while surface hoar has been buried on shaded aspects above 1600m. Below this layer lies a second crust/surface hoar interface buried early-January that is now 50-90 cm below the surface.

The mid-December surface hoar layer is buried 100-140 cm below the surface. This spooky layer still produces "sudden" test results and is most pronounced at treeline, but is also present below treeline .

Two laminated crusts created by rain events in late November lay just below the mid-December interface, and may co-exist with facets.

Weather Forecast

Tuesday Night: 10-15cm of new snow / Moderate to strong southwesterly ridgetop winds / Freezing level around 700m.

Wednesday: 15-20 cm of new snow / Moderate to strong southerly ridgetop winds / Freezing level rising to around 1400m.

Thursday: Mostly cloudy with isolated flurries / Light to moderate southerly ridgetop winds / Freezing level dropping to around 900m.

Friday: Mostly cloudy with isolated flurries / Light to moderate southwesterly ridgetop winds / Freezing level dropping to around 500m.

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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