Avalanche Forecast

South Coast Inland

Date issued

Nov 25, 2017 - 3:54 PM

Valid until

Nov 26, 2017 - 2:00 PM

Prepared by

cgarritty

A natural avalanche cycle is expected on Sunday with rain set to batter the snowpack. Conditions will be especially dangerous where rain falls on dry snow. This will certainly be the case at high elevations in the south of the region.

Regular season
Saturday - November 25, 2017
Alpine

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.

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

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.

Sunday - November 26, 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.

Monday - November 27, 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

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.

Avalanche Problem 1: Storm Slabs

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

Rain will be a powerful trigger for slab avalanches on Sunday as it rapidly loads and warms the upper snowpack where dry snow lies on the surface. Touchy new slabs may also form at higher elevations in the region's north as rain transitions to snow.

Travel and Terrain Advice
  • Avoid exposure to areas with overhead hazard during periods of rain.
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Avalanche Problem 2: Loose Wet

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

Warm, wet weather will destabilize surface snow and encourage loose wet avalanching on Sunday, especially in steep terrain. Even a small release can develop into a very dangerous problem as it gathers mass traveling downslope.

Travel and Terrain Advice
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.
  • Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.

Avalanche Summary

No new avalanches have been reported, however new storm slabs developed at upper elevations in the south of the region over last week's stormy weather. Please post your observations to the Mountain Information Network. (MIN)

Snowpack Summary

Up to 10 cm of new snow lies on the surface above about 1300 metres in the north of the region, with up to 35 cm in the south. Recent southerly winds have redistributed the new snow into wind slabs in lee terrain. Areas that received more snow may still be presenting a more generalized storm slab problem on all aspects. Below the new snow, last week's warm and wet weather saturated the snowpack with rain. This will have refrozen into a strong capping crust below the new snow at higher elevations but may remain moist below treeline and into the valley bottom. Below this variable crust interface the heavy rain eroded snowpack depths significantly, leaving behind a rain-soaked and relatively uniform 90 cm at treeline elevations throughout the region.

Weather Forecast

Sunday: Approximately 20mm of rain in the south of the region with 10-15 cm of new snow at alpine elevations in the north. Rain below about 1700 metres. Strong south winds. Freezing level ranging from 2000-2200 metres with alpine temperatures from +3 in the south to around 0 in the north.

Monday: Mainly cloudy with isolated flurries and a trace of new snow in the north of the region. A possible 5 cm of new snow in the south. LIght to moderate southwest winds. Freezing level to around 1200 metres with alpine temperatures of -5 in the north of the region and -3 in the south.

Tuesday: Cloudy with scattered flurries and approximately 5 cm of new snow at higher elevations. Rain below about 1200 metres. Strong southwest winds. Freezing level to about 1600 metres with alpine temperatures from about -1 in the south of the region to -3 in the north.

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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