Date issued

Dec 19, 2017 - 8:12 AM

Valid until

Dec 20, 2017 - 8:00 AM

Prepared by

ross campbell

Skier or Rider triggered avalanches are likely today. Now is a good time to step back and make conservative terrain choices.

Regular season
Tuesday - December 19, 2017
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.

Wednesday - December 20, 2017
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.

Thursday - December 21, 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

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: Storm Slabs

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

Yesterday's storm snow is settling into a slab. It will be reactive in windy areas in the Alpine and exposed areas at Tree Line. Steep solar asp will be problematic, as there will be a crust under our slab and a Surface Hoar/Facet combo BTL.

Travel and Terrain Advice
  • Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.
  • Use conservative route selection, stick to supported terrain features, avoid overhead hazards.

Avalanche Summary

A Widespread natural avalanche cycle occurred yesterday morning up to size 2.5 in the highway corridor. Avalanches were mainly size 1.5 to 2 and all failing as a soft slab on the Dec 15th Surface Hoar Layer. Avalanches initiated on all aspects and elevations yesterday, see attached pic of a below tree line slab avalanche. low elevation avalanches

Snowpack Summary

40cm of storm snow now overlies the Dec 15th Surface Hoar/Persistent Weak Layer. On steep solar aspects, there is a sun crust also buried under the new snow, reaching well into the Alpine from last week's inverted temperatures. Throughout the snowpack there are multiple crusts, which are currently bonded well to neighboring layers.

Weather Forecast

A Low-Pressure system slides South of Rogers Pass, while a large High-Pressure moves in from the NE. As these two weather patterns duke it out, we'll accumulate 5-10cm of new snow, moderate Northerly winds and cold temperatures in the -10 range. 5cm tonight and plummeting temperatures into the future as the High-Pressure dominates our region.

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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