Date issued

Jan 10, 2018 - 8:00 AM

Valid until

Jan 11, 2018 - 8:00 AM

Prepared by

percy woods

A touchy storm slab sits on top of a sensitive surface hoar layer primed for human triggering.  Time to be conservative in your trip plans! Make low angle, low consequence terrain choices!

Regular season
Wednesday - January 10, 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.

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.

Avalanche Problem 1: Storm Slabs

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

45cm of recent storm snow is settling into a slab assisted by warm temperatures (-1 to -5). The Jan 4 surface hoar is down ~45cm and found to be up to 15mm in size. If triggered, small avalanches could step down to the Dec 15th PWL with big results.

Travel and Terrain Advice
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Avalanche Problem 2: Persistent Slabs

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

The Dec 15th PWL is widespread around tree line and below tree line, buried ~80cm. New snow and warm temps have slabbed up the upper snow pack! This interface became reactive Monday, burying one skier in a terrain trap.

Travel and Terrain Advice
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.

Avalanche Summary

Tuesday's avalanche control produced numerous size 3 slab avalanches with one size 4. Monday a skier was fully buried by a self triggered slide releasing on the Dec 15 layer. Also reported Monday were several skier controlled avalanches to size 1.5 reported from the backcountry and skier remotes from 10m away, failing on the Jan 4 layer.

Snowpack Summary

45cm of storm snow resides over the Jan 4 interface and the Dec 15 surface hoar (PWL) is down ~75cm. Monday through Tuesday was a tipping point of storm snow over weak layers. Snowpack tests show propagation potential and a high likelihood for skier triggering. The Dec 15th Surface Hoar layer is most reactive at tree line and below.

Weather Forecast

Alpine high of -10C with light precipitation and moderate W'ly winds. Thursday through Friday looks like light snow, cool temperatures and shifting light to moderate winds first SE on Thursday and back to W on Friday.

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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