Date issued

Jan 30, 2018 - 4:35 PM

Valid until

Jan 31, 2018 - 4:00 PM

Prepared by

aaron beardmore

Large and destructive avalanches are likely. Step way back and avoid avalanche terrain. Avalanche control is planned for Mt. Bosworth, Mt. Dennis Mt. Field and Mt. Whymper tomorrow. No activity permitted in these areas.

Regular season
Tuesday - January 30, 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.

Wednesday - January 31, 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.

Thursday - February 1, 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.

Avalanche Problem 1: Persistent Slabs

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

There are three weak layers 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. Avalanches are occurring on these layers and human triggering is almost certain.

Travel and Terrain Advice
  • Use conservative route selection, choose supported terrain with low consequence.
  • Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Avalanche Problem 2: Wind Slabs

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

Recent winds and new snow have formed slabs in leeward areas of alpine and treeline terrain, and caused natural avalanches. The slabs are plump and ripe for triggering, and will likely step down to persistent weak layers.

Travel and Terrain Advice
  • If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.
  • Use caution in lee areas. Recent wind loading have created wind slabs.

Avalanche Summary

A major cycle is upon us. Avalanche control today produced results up to size 3.5 with deep fractures and wide propagations. Basically, avalanches could been seen anywhere a forecaster looked today.

Snowpack Summary

Recent storms have deposited 45-85cm of storm snow in the last 7 days. Increasing wind and steady snowfall today are loading 3 persistent weak layers of surface hoar and facets in the upper half of the snowpack: Jan 16 down 25-45cm; Jan 6 down 35-55cm; and Dec15 down 45-80cm. In snowpits, these layers are giving sudden test results.

Weather Forecast

Wednesday will present a slight cooling trend and an easing of precipitation. However, Thursday will see the temperatures rise and the precip return. By Friday the storm will intensify a deposit up to another 30cm by the end of the weekend. Obviously, this will contribute to a rise in the danger rating.

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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