Avalanche Forecast

Kootenay Boundary

Date issued

Nov 26, 2017 - 3:28 PM

Valid until

Nov 27, 2017 - 2:00 PM

Prepared by

mgrist

The effects of warm temperatures and rain on the snowpack may linger into Monday. Due to limited data it is CRITICAL to supplement this information with your own observations. Please post your observations to the MIN.

Regular season
Sunday - November 26, 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 - November 27, 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.

Tuesday - November 28, 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?

The rain and warm temperatures from Sunday could remain a factor in the upper snowpack depending on how quickly it cools off overnight into Monday. Even a small avalanche can push you into terrain traps.

Travel and Terrain Advice
  • Watch out for wet sloughs in steep terrain, particularly where the debris flows into terrain traps.

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

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

Approximately 4-6 cm of snow fell Saturday night into Sunday, followed by rapidly warming temperatures on Sunday morning (to +3 Celsius at ridge crest in many locations).

This new snow (or what's left of it) sits on the thick Nov 23rd rain crust, that formed at the end of last week's Atmospheric River (aka Pineapple) event.

The depth of the snowpack varies greatly with elevation. Recent reports suggest the average depth is 100+cm 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 thick November 23rd crust 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

There may be some lingering flurries on Monday with more seasonal temperatures. The next system arrives on Tuesday, with lower freezing levels than we've been seeing lately.

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

TUESDAY: Flurries (10-15cm possible). Light-moderate southerly ridgetop winds. Freezing level around 1000 m.

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