Date issued

Feb 23, 2018 - 4:00 PM

Valid until

Feb 24, 2018 - 4:00 PM

Prepared by

tim haggarty

A firm slab, sitting over several persistent weak layers, is found throughout the forecast region and remains a high consequence concern for human triggering. Continue to travel conservatively especially in the low alpine and around treeline areas.

Regular season
Saturday - February 24, 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

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.

Sunday - February 25, 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

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 - February 26, 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

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: Persistent Slabs

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

A stiff slab 50 to 80cm thick, sits over: Sun Crusts (south and west aspects), Surface Hoar (at, and just above treeline) and weak Faceted Crystals (very developed in shallow snowpack features) This is a dangerous problem that is difficult to avoid.

Travel and Terrain Advice
  • Use conservative route selection, stick to supported terrain features, avoid overhead hazards.
  • Avoid shallow snowpack areas where triggering is more likely.

Avalanche Problem 2: Wind Slabs

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

Expect hardslabs in the alpine and a few softer slabs at treeline. The cold has kept these in check and helped these settle well over the last few days but some caution is still warranted with the expected warming and increased wind this weekend.

Travel and Terrain Advice
  • If triggered the wind slabs may step down to deeper layers resulting in large avalanches.
  • The best powder will be found in sheltered locations at or below treeline.

Avalanche Summary

Minimal evidence of recent activity exists: mainly small windslabs in the S and W facing alpine. Widespread wind effect is evident. An extensive cycle was seen as the persistent slab became overloaded with successive storms. Avalanches to sz 3.5 were observed from most aspects and most elevations with the majority of the action seen around 21-2500m

Snowpack Summary

Previous Strong winds from W and N directions have left wind slabs and wind effect in open areas. The upper snowpack has settled to form a cohesive stiff slab that is sitting on three persistent weak layers mid-pack (down 50 to 80cm) which can be found throughout the forecast region, and have produced many large avalanches that have run full path.

Weather Forecast

A series of minor disturbances are tracking N- S against the west side of the Rockies through midweek. One of these systems is passing Friday, the next Saturday night. Small amounts of precip, temps rising to -10 at treeline Saturday and Sunday and increased westerly winds are likely. Cooling again on Monday before another system slides past. 

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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