Avalanche Forecast

Lizard Range and Flathead

Date issued

Dec 5, 2017 - 4:39 PM

Valid until

Dec 6, 2017 - 2:00 PM

Prepared by

cgarritty

Change is in the air with strong solar effect and the beginning of a warming trend in the forecast. These two factors will begin to undermine stability on Wednesday.

Regular season
Wednesday - December 6, 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

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 7, 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

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.

Friday - December 8, 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

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?

Avalanche activity has become increasingly localized to wind affected and lee areas where wind slabs have been building. Be especially cautious of cross-loaded slopes that see sun exposure on Wednesday.

Travel and Terrain Advice
  • Be careful with wind loaded areas, especially near ridge crests and roll-overs.
  • Minimize exposure to sun exposed slopes when the solar radiation is strong.

Avalanche Summary

Reports from Monday showed a couple of wind slabs releasing naturally and with ski cutting to Size 1.5 in the Fernie area. On Sunday, avalanche control with explosives triggered numerous size 1 dry loose avalanches above 1900 m from northeast aspects.

Please submit your observations to the Mountain Information Network (MIN).

Snowpack Summary

Recent winds have been redistributing loose snow at higher elevations and forming wind slabs on leeward slopes and terrain features. Below the surface, 40-60 cm of accumulated storm snow now sits above the crust that formed a week ago. The buried crust is supportive and approximately 25 cm thick. It extends from 1600 m to mountain top elevations on all aspects. The bond of our recent storm snow to this crust is expected to be strengthening gradually and it has produced hard, resistant results in recent snowpack tests. Below this interface, the snowpack is moist to ground. The average snowpack depth at treeline is 60-80 cm while a deeper snowpack exists in the alpine.

Weather Forecast

Wednesday: A mix of sun and cloud. Light west winds. Alpine temperatures rising to around -2 during the day, increasing in the evening with the onset of an alpine temperature inversion.

Thursday: A mix of sun and cloud with some low valley cloud due to a strong alpine temperature inversion. Light west winds. Freezing level rising from 2700 to 3300 metres over the day with alpine temperatures around +4. Cooler at lower elevations.

Friday: Mainly sunny with some valley cloud due to lingering alpine temperature inversion. Light west winds. Freezing level to 3300 metres with alpine temperatures around +6.

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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