Date issued

Feb 1, 2018 - 4:00 PM

Valid until

Feb 2, 2018 - 4:00 PM

Prepared by

stephen holeczi

There's plenty of loose snow available for transport, and big winds are forecast for Friday and Saturday. This in conjunction with incoming snow will likely induce another avalanche cycle.

Regular season
Friday - February 2, 2018
Alpine

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.

Treeline

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.

Below 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.

Saturday - February 3, 2018
Alpine

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.

Treeline

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.

Below Treeline

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.

Sunday - February 4, 2018
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

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.

Avalanche Problem 1: Persistent Slabs

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

Three weak layers exist in the upper snowpack: Jan 16, Jan 6, and Dec 15. All are a mix of sun crust, surface hoar and facets depending on your aspect and elevation. Destructive avalanches have occurred on these and will continue over the few days.

Travel and Terrain Advice
  • Avoid all avalanche terrain.
  • Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Avalanche Problem 2: Wind Slabs

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

With plenty of loose snow around, incoming wind will form slabs quickly, adding to existing ones. The slabs are plump and ripe for triggering, and will likely step down to persistent weak layers.

Travel and Terrain Advice
  • Avoid all avalanche terrain.
  • If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Avalanche Summary

Natural activity has tapered slightly, but big results with explosives over the last few days to size 3.5 proves that these layers are prime for triggering. Some avalanches ran full path and put dust or debris on roads.  Many slopes haven't slid yet, and any additional input (snow/wind/human) will overload the snowpack.

Snowpack Summary

40-80 cm of snow over the last seven days has overloaded 3 persistent weak layers of surface hoar and facets in the upper half of the snowpack: Jan 16 down 30-50cm; Jan 6 down 40-70cm; and Dec15 down 50-100+cm. A major avalanche cycle occurred Monday/Tuesday with avalanches running fall path on these layers and some stepping down even deeper.

Weather Forecast

Fridays big story will be the forecasted alpine winds in the 70 - 100kmh range and rising temperatures in front of the next system. Banff is forecast only for a couple cm, and Lake Louise in the 10cm range. By Saturday night Banff could see 10cm and regions near the divide could see 20+ cm. We expect another avalanche cycle given this forecast.

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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