Avalanche Forecast

Northwest Coastal

Date issued

Nov 30, 2017 - 3:54 PM

Valid until

Dec 1, 2017 - 2:00 PM

Prepared by

swerner

The recent stormy weather has dumped as much as 110 cm of new snow on last week's crust. This has created reactive storm slabs and there have been reports of large avalanches. Use a conservative approach and terrain selection.

Regular season
Thursday - November 30, 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

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.

Friday - December 1, 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

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.

Saturday - December 2, 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

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?

Building storm slabs will be most prominent and reactive to rider triggers above treeline especially where the storm snow has been affected by the wind.

Travel and Terrain Advice
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • The new snow will require several days to settle and stabilize.
  • Be cautious as you transition into wind affected terrain.

Avalanche Problem 2: Deep Persistent Slabs

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

This layer has been inactive. However, with the increasing load of new snow this layer may become reactive. Something to keep on your radar.

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

Avalanche Summary

No recent natural avalanche activity has been reported. On Wednesday, an explosive triggered slab avalanche was reported up to size 2.5 in the alpine. The aspect is unknown. Earlier in the week, observations from the Shames area reported audible avalanches from across the valley and shooting cracks within the recent storm snow. The recent storm snow will likely take time to settle and bond. Travel in avalanche terrain will require conservative route selection and terrain choices. Please send your recent observations to the Mountain Information Network. Give info get info.

Snowpack Summary

Snow accumulations of 80-100 cm of storm snow in the southern part of the region now lies on the supportive 5-10 cm thick, November 23 rain crust from last week. Winds associated with the new snow has formed reactive wind slabs on leeward slopes. Below this crust is a weak layer that formed in late October and is now buried 120-160 cm within the snowpack. Beneath this October crust is a 20-30 cm thick layer consisting of several thin crusts and facets (sugary snow). Recent snowpack tests and observations indicate that that the new snow is likely reactive to rider triggers.
Reports further north near Ningunsaw, describe a much shallower facetted snowpack 60-120 cm.

Weather Forecast

Friday: Snow amounts 5-15 cm with moderate South West wind. Alpine temperature -5. Freezing level 500 m and dropping.

Saturday: Snow amounts 5-10 cm with light to moderate South West wind. Alpine temperature -7. Freezing level valley bottom.

Sunday: Mix of sun and cloud. Light to moderate North West wind. Alpine temperature -7. Freezing level valley bottom.

Visit the Mountain Weather Forecast for more details.

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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