Avalanche Forecast

Kootenay Boundary

Date issued

Nov 27, 2017 - 4:28 PM

Valid until

Nov 28, 2017 - 2:00 PM

Prepared by

mgrist

New snow and southerly winds will be driving the avalanche danger on Tuesday. Due to limited data it is CRITICAL to supplement this information with your own observations. Please post your observations to the MIN.

Regular season
Monday - November 27, 2017
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.

Tuesday - November 28, 2017
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

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.

Wednesday - November 29, 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.

Avalanche Problem 1: Storm Slabs

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

New snow on Tuesday will sit on a 2 cm thick melt-freeze crust, which will likely act as a good sliding layer.

Travel and Terrain Advice
  • Minimize overhead exposure during periods of heavy loading from new snow, wind.
  • Use caution in lee areas. Recent wind loading has created wind slabs.

Avalanche Problem 2: Persistent Slabs

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

Recent rain to mountaintops combined with overnight cooling has reduced the likelihood of triggering this layer. Areas in which the snowpack above this layer remained dry should be treated with increased caution.

Travel and Terrain Advice
  • Use increased caution in areas which did not form a surface crust.
  • Avoid shallow snowpack areas where triggering is more likely.

Avalanche Summary

No new avalanches reported; however, we currently have very limited observations in this region. Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Anywhere from 2-10 cm of snow fell Sunday overnight into Monday, as temperatures dropped by 5-10 degrees (and back to more seasonal values). Ridge top winds were moderate from the west and likely formed wind slabs on lee (easterly) slopes.

This new snow fell on a 2 cm thick melt-feeze crust, which could become a good sliding layer when more snow falls on Tuesday.

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.

Last week's heavy rain to the mountaintops really shrunk the snowpack and has transitioned much of the snowpack from dry to moist snow. A major feature in the snowpack is a crust which formed at the end of October and may exist approximately 30cm above the ground in some locations. That said, the latest crust (November 27th) will temporarily reduce the likelihood of triggering on this layer.

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

Weather Forecast

The next system arrives on Tuesday with modest amounts of snow and more seasonal freezing levels.

TUESDAY: Snow (10-15 cm) during the day with another 5-10 cm possible overnight. Moderate southerly ridgetop winds. Freezing level around 1000 m.

WEDNESDAY: Clearing throughout the day. Moderate westerly ridgetop winds. Freezing level around 1200 m.

THURSDAY: Cloudy with isolated flurries. Light to moderate southwesterly ridgetop winds. Freezing level around 1000 m.

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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