Avalanche Forecast

Kootenay Boundary

Date issued

Dec 10, 2017 - 4:01 PM

Valid until

Dec 11, 2017 - 2:00 PM

Prepared by

mconlan

Shady slopes offer the best snow. Isolated wind slabs may exist at high elevations.

Regular season
Sunday - December 10, 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.

Monday - December 11, 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.

Tuesday - December 12, 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: Wind Slabs

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

Increased winds may have produced wind slabs in lee features. These may sit on lingering slabs from last week.

Travel and Terrain Advice
  • If triggered, wind slabs may step down to deeper layers resulting in large avalanches.
  • Avoid wind-loaded pockets near ridges.

Avalanche Problem 2: Loose Wet

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

Warm air temperatures and clear skies have produced spring-like conditions on steep solar aspects. Loose wet avalanches may begin small but could step down to deeper crust layers.

Travel and Terrain Advice
  • Avoid sunny slopes when the solar radiation is strong, especially if the snow is moist or wet.
  • Use caution above cliffs and terrain traps, where small avalanches may have severe consequences.
  • Loose wet avalanches may trigger deeper layers resulting in large avalanches.

Avalanche Summary

Small loose dry avalanches were observed from skier traffic in steep terrain on Saturday. Small wind slabs were released on Friday by a skier and explosives in alpine lee features. Small loose wet avalanches were observed on steep south-facing slopes on Thursday.

Snowpack Summary

Moderate winds from the west and northwest may have formed wind slabs in southerly and easterly lee features. These may sit above lingering slabs from last week. The warm air temperatures and clear skies from the past few days have caused melting of the surface snow on south-facing slopes near treeline and above. Crusts may form overnight but should melt quickly in the mornings if clear skies prevail. Dry snow is generally found on shady slopes and below treeline, which may produce sluffing in steep terrain. Surface hoar to 30 mm has been observed along with near-surface faceting in the top 20 cm of the snowpack. Beneath this, the snowpack has settled and may be improving the bond to the 30-50 cm deep rain crust from late November. However, there are still limited observations of this crust layer. On ridges, cornices may be weakening with the warm air temperatures.

Weather Forecast

MONDAY: Clear skies with valley clouds, light westerly winds, freezing level around 3600 m with below-freezing temperatures in the valleys.

TUESDAY: Mostly clear skies with valley clouds, light to moderate westerly winds, freezing level dropping to 2500 m with below-freezing temperatures in the valleys.

WEDNESDAY: Partly cloudy with valley clouds, light northwesterly winds, freezing level around 2500 m with below-freezing temperatures 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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