Avalanche Forecast

Kootenay Boundary

Date issued

Dec 6, 2017 - 4:15 PM

Valid until

Dec 7, 2017 - 2:00 PM

Prepared by

shorton

Avoid south slopes. They have been wind loaded and will become weak with the intense warming and sun.

Regular season
Thursday - December 7, 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.

Friday - December 8, 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.

Saturday - December 9, 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.

Avalanche Problem 1: Loose Wet

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

Conditions will be more like spring than winter starting Wednesday. Surface snow layers can become weak when hit by the sun. Minimize your exposure to terrain traps - even small sluffs can push you into dangerous terrain.

Travel and Terrain Advice
  • Use caution above cliffs and terrain traps where small avalanches may have severe consequences.
  • Use extra caution on sunny slopes or if the snow is moist or wet.

Avalanche Problem 2: Wind Slabs

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

Winds from the northwest have formed hard slabs on south and east facing slopes. Be careful on steep convex terrain or where the wind has blown the snow into more cohesive slabs.

Travel and Terrain Advice
  • Be alert to changing snow conditions, especially where the snow firms up or sounds hollow.
  • Be careful with wind loaded pockets on downwind (south east facing) slopes.

Avalanche Summary

On Tuesday, a small (size 1) natural storm slab avalanche was reported on a southeast slope at 2150 m. Previous activity from the weekend included some larger natural and skier triggered storm slabs up to size 2, with the largest cause by recent loading from northwest winds.

Snowpack Summary

Dramatic warming will cause widespread melting of the surface snow, especially on south-facing slopes. Crusts may form overnight, but will melt quickly in the mornings. 30 - 50 cm of new snow has fallen in the past week. At higher elevations, northwest winds redistributed the snow, forming wind slabs on downwind (lee) features. Below the recent storm snow you'll likely find a couple of widespread crusts (2 to 5 cm thick) which formed as a result of late November's rain. The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 100-170 cm in the alpine, 50-100 cm at treeline, and decreasing rapidly below treeline where the primary hazards are rocks, stumps, and open creeks.

Weather Forecast

THURSDAY: Alpine sun with some valley clouds, light northwest wind, freezing level around 3300 m with inversions in the valleys.

FRIDAY: Alpine sun with some valley clouds, light northwest wind, freezing level around 3000 m with inversions in the valleys.

SATURDAY: Increasing cloud, moderate west wind, freezing level around 2700 m with inversions in the valleys.

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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