Avalanche Forecast

North Columbia

Date issued

Mar 6, 2018 - 4:07 PM

Valid until

Mar 7, 2018 - 2:00 PM

Prepared by

pgoddard

Avalanche danger will spike higher than forecast on slopes that are being cooked by the sun.

Regular season
Tuesday - March 6, 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.

Wednesday - March 7, 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.

Thursday - March 8, 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: Persistent Slabs

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

Persistent slabs are most likely to be triggered with a large load like cornice fall; or by a person in a thin or variable-depth snowpack spot. Solar warming could make the slab easier to trigger too.

Travel and Terrain Advice
  • Avoid convoluted terrain with variable or shallow snow depths and multiple trigger points.
  • Pay attention to overhead hazards like cornices which could trigger persistent slabs.
  • Minimize exposure to steep, sun exposed slopes, especially when the solar radiation is strong.

Avalanche Problem 2: Wind Slabs

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

Recent variable winds have left behind slabs in the lee of ridges and ribs. Cornices are fragile and may fall with solar warming.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • Extra caution needed around cornices with current conditions.
  • Be cautious as you transition into wind affected terrain.

Avalanche Summary

On Monday, a few large slabs were reported. A size 3 persistent slab was remotely triggered by a skier in the east of the region. A couple more large naturally-triggered slabs were reported as failing on the February persistent weak layers on south to west aspects.

Snowpack Summary

Recent storm snow continues to settle and dry out. Variable recent winds have left behind wind slabs on many slopes at treeline and above. These are expected to heal within a day or two. Direct sun is likely to weaken surface snow layers and give cornices a bit of an extra nudge too.

A couple of layers buried in mid-late February (down around 50-100 cm) are variably reactive, but both have the potential to create surprisingly large avalanches if triggered. Initially, this interface was most reactive on solar aspects, where it presents as a buried sun crust. However, it has been triggered on shady aspects too, where surface hoar and/or facets exist.

Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with significant warming, a surface avalanche stepping down, a cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. Facets linger at the base of the snowpack.

Weather Forecast

WEDNESDAY: Mix of sun and cloud with flurries. Treeline temperature near -10. Light south-westerly winds.

THURSDAY: Cloud increasing. 5-10 cm snow overnight. Treeline temperature near -8. Light south-westerly winds.

FRIDAY: Mix of sun and cloud with flurries. Treeline temperature near -5. Light westerly winds.

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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