Avalanche Forecast

South Coast Inland

Date issued

Dec 10, 2017 - 3:52 PM

Valid until

Dec 11, 2017 - 2:00 PM

Prepared by

mconlan

Temperature inversion conditions have moistened the snow surface at higher elevations.  This is likely on all aspects in the north of the region and predominantly on southerly slopes in the south of the region.

Regular season
Sunday - December 10, 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.

Monday - December 11, 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.

Tuesday - December 12, 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?

Increased winds from the south may have produced wind slabs, particularly behind ridges in alpine terrain. Be cautious of firm snow when entering lee features.

Travel and Terrain Advice
  • Avoid wind-loaded pockets near ridges.

Avalanche Problem 2: Loose Wet

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

Warm air temperatures and clear skies have produced spring-like conditions on steep, sun-exposed slopes. Northerly slopes may also warm up under cloudy skies. Loose wet avalanches may begin small but can grow and push you into dangerous terrain.

Travel and Terrain Advice
  • Avoid sunny slopes when the solar radiation is strong, especially if the snow is moist or wet.
  • Use caution above cliffs and terrain traps, where small avalanches may have severe consequences.

Avalanche Summary

Numerous loose wet avalanches up to size 2 were observed on northerly aspects along Duffey Lake Road on Sunday. No new avalanches were observed on Friday or Saturday. Numerous small loose wet avalanches (size 1) were observed on steep south and west-facing slopes on Wednesday and Thursday. Glide avalanches were observed on steep, smooth rock slabs to size 2 around the Coquihalla on Thursday.

Snowpack Summary

Warm air temperatures and sunny skies have created surface crusts on southerly slopes, which may melt with warm air temperatures and under sunny skies.  North slopes were also affected in areas where cloudy skies prevailed on Sunday, due to the greenhouse effect.  It appears that this mostly occurred in the northern half of the region.  For the southern half of the region, northerly slopes likely remained cold.  Moderate wind speeds from the south may have produced localized wind slabs on northerly lee features. In shady slopes, surface hoar to 20 mm and near-surface faceting have been observed around treeline and in the alpine.  Cornices may be weakening with the warm air temperatures. The recent snow has formed a strong bond to the late November rain crust, which is now 30-50 cm deep. Treeline snow depths are approximately 1 m throughout the region.

Weather Forecast

MONDAY: Clear skies, light southwesterly winds increasing to moderate in the afternoon, freezing level around 3700 m with inversion conditions.

TUESDAY: Partly cloudy, light southwesterly winds, freezing level around 2300 m with inversion conditions.

WEDNESDAY: Mostly clear skies, light northwesterly winds, freezing level rising to 3500 m over the day with inversion conditions.

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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