Avalanche Forecast

Northwest Coastal

Date issued

Feb 2, 2018 - 6:14 PM

Valid until

Feb 3, 2018 - 2:00 PM

Prepared by

shorton

Stormy weather will elevate the danger this weekend. Minimize your exposure to avalanche terrain when there's rapid loading from new snow and wind.

Regular season
Friday - February 2, 2018
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.

Saturday - February 3, 2018
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.

Sunday - February 4, 2018
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

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.

Avalanche Problem 1: Storm Slabs

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

Fresh storm slabs are building and will be very touchy at higher elevations and in wind-affected terrain.

Travel and Terrain Advice
  • Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Minimize exposure during periods of heavy loading from new snow and wind.
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Avalanche Problem 2: Persistent Slabs

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

A weak layer buried 60-100 cm below the surface has potential for human triggering. Storm slab avalanches may also step down to this layer.

Travel and Terrain Advice
  • Avoid areas with overhead hazard.
  • Caution around convexities or areas with a thin or variable snowpack.

Avalanche Summary

Natural avalanche activity was observed on Friday morning, producing several 30 cm thick slabs in the latest snow.

A few persistent slab avalanches released on Wednesday, most likely failing on the mid-January crust. This includes a natural size 3 avalanche on a southwest slope at 1150 m near Exstew, a few skier triggered slabs (size 1-2) in thinner snowpack areas (east of Terrace and the northern part of the region). The mid-January layer was also active in the Shames area last Saturday, where a skier triggered a size 2 avalanche on a northeast alpine slope. In this case, the weak layer was composed of surface hoar. Overall, activity on persistent weak layers has been limited recently, but enough to suggest these layers may remain reactive through this current storm.

Snowpack Summary

Fresh snow will continue to accumulate the next few days. In some areas up to a metre of storm snow has already accumulated over the past week. Warm temperatures are promoting the settlement of new snow, while westerly winds are blowing snow around in exposed areas.

A weak layer buried in mid-January remains a concern and is now 60-100 cm deep. In most areas this layer is a crust, but it may also be surface hoar in sheltered areas at treeline and below. This layer produced a few human triggered avalanches throughout the region over the past week, and may remain reactive as it adjusts to the weight of the new snow.

In thinner snowpack areas (north and inland), deeper crust / surface hoar layers that were buried in December and early January may still be a concern. They are buried over 100 cm below the surface, but may be triggerable from thin spots.

Weather Forecast

SATURDAY: 10-20 cm Friday night then clearing and cooling throughout the day, strong northwest wind, freezing level dropping back to valley bottom.

SUNDAY: The next system arrives Sunday morning delivering 10 cm snow throughout the day and continuing into the evening with another 15-30 cm Sunday night, moderate west wind, alpine high temperatures around -8 C.

MONDAY: Clearing throughout the day with isolated flurries, light to moderate southwest wind, alpine high temperatures around -5 C.

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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