Date issued

Jan 12, 2018 - 8:04 AM

Valid until

Jan 13, 2018 - 8:00 AM

Prepared by

andrew jones

Human-triggered avalanches are likely with several buried surface hoar layers. It's time for conservative decision making.

Regular season
Thursday - January 11, 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.

Friday - January 12, 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.

Saturday - January 13, 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: Storm Slabs

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

A reactive storm slab sits atop the Jan 4 surface hoar interface. The slab is poorly bonded where the surface hoar is well preserved. If triggered, avalanches could step down to the Dec 15th persistent weak layer causing very large slides.

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

Avalanche Problem 2: Persistent Slabs

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

This interface has become reactive with the recent new snow loading. It is most prevalent around treeline or on sheltered slopes the alpine. These avalanches are especially dangerous in terrain trap features where debris can pile up quickly.

Travel and Terrain Advice
  • Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.
  • Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

Avalanche Summary

A size 3 natural avalanche occurred yesterday morning on the SE face of 8812 peak. A field team observed evidence of a slightly older widespread natural avalanche cycle while traveling in Connaught Creek drainage. A second field team felt a large whumph while descending through an open glade in the Hermit area.

Snowpack Summary

70cm of snow fell in the past week and settled into a slab over several weak layers. Jan 4th surface hoar is down 50cm and the Dec 15 surface hoar persistent weak layer is down around 100cm. The additional snow load has made these layers reactive. Snowpack tests show propagation potential with sudden planar results on the Jan 4 and Dec15 layers.

Weather Forecast

Cloudy with sunny periods today. Freezing levels climb to 800m with an alpine high of -8.0. Winds will be light from the SW.  Cold arctic air will be replaced by a SW flow on Saturday bringing warmer temperatures, strong winds and trace amounts of snow.  Freezing levels reach 1700m on Sunday.  Up to 20cm of snow is expected for Tuesday.

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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