Avalanche Forecast

Lizard Range and Flathead

Date issued

Dec 11, 2017 - 3:59 PM

Valid until

Dec 12, 2017 - 2:00 PM

Prepared by

swerner

Triggering wind slabs remain a possibility. Seek sheltered terrain and shady aspects for decent riding conditions.

Regular season
Tuesday - December 12, 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

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.

Below Treeline

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.

Wednesday - December 13, 2017
Alpine

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.

Treeline

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.

Below Treeline

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.

Thursday - December 14, 2017
Alpine

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.

Treeline

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.

Below Treeline

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.

Avalanche Problem 1: Wind Slabs

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

Variable winds from last week have formed wind slabs on a wide range of aspects at higher elevations.

Travel and Terrain Advice
  • Use ridges or ribs to avoid pockets of wind loaded snow.
  • Be careful with wind loaded areas, especially near ridge crests and roll-overs.

Avalanche Summary

On Sunday, avalanche control using explosives produced avalanches up to size 1. On Monday, loose wet avalanche activity was observed from steep S-SW slopes up to size 1.

Please submit your observations to the Mountain Information Network.

Snowpack Summary

A variety of snow surfaces exist throughout the region. Stiff wind slabs sit on a wide range of aspects on alpine and exposed treeline slopes. In sheltered treeline and below treeline terrain, I suspect light amounts of low-density snow intermingle with surface hoar and surface facets.

Roughly 30-60 cm below the surface you'll likely find a hard crust that was buried near the end of November. This crust is approximately 30 cm thick and extends from 1600 m to mountain top on all aspects. Below this crust, the snowpack is moist to ground. Average snowpack depths at treeline elevations in the region range from 80-120 cm.

Weather Forecast

Fairly benign weather pattern for the forecast period.

Tuesday: Mostly cloudy. Alpine temperatures near -4 and freezing levels at valley bottom. Ridgetop winds light from the west.

Wednesday: Cloudy with possible sunny breaks. Alpine temperatures near -5 with light west winds.

Thursday: Mainly cloudy. Alpine temperatures near -7 with ridgetop winds light west.

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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