Avalanche Forecast

Northwest Inland

Date issued

Feb 2, 2018 - 6:34 PM

Valid until

Feb 3, 2018 - 2:00 PM

Prepared by

shorton

Heavy accumulations are possible as an Arctic front sits over the region. Be extra cautious if there's lots of new snow or strong wind.

Regular season
Friday - February 2, 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.

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

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

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: Storm Slabs

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

New snow and strong wind will form touchy slabs, especially at higher elevations and in wind-affected terrain. Weather forecasts are handling the situation poorly, so some areas may have extra thick and touchy storm slabs.

Travel and Terrain Advice
  • If triggered the wind slabs may step down to deeper layers resulting in large 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?

There is limited information about weak layers buried 30-80 cm below the surface. They produced a few avalanches earlier this week, and may still be reactive. Carefully assess the snowpack and terrain in your local area.

Travel and Terrain Advice
  • Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.
  • Evaluate unsupported slopes critically.
  • Avoid lingering in runout zones.

Avalanche Summary

Reports have been limited recently. Skiers have been able to trigger a few small slabs on steep convex rolls on Thursday and Wednesday. Some evidence of past natural activity has been reported in various parts of the region, likely occurring during last week's storm.

A few persistent slab avalanches have been reported over the past week as well. Several naturally-triggered size 2 persistent slab avalanches failed naturally at 1200 m in the Howsons on Tuesday. A large naturally-triggered size 3 persistent slab avalanche was reported on an east aspect at 1900 m in the Howsons on Monday. Two large remotely triggered avalanches (size 2.5) were reported on north and west aspects around 1600 m north of Kispiox late last week.

Snowpack Summary

Fresh snow will continue to accumulate the next few days. 20-30 cm has already accumulated since Thursday. Warm temperatures are promoting the settlement of new snow, while westerly winds are blowing snow around in exposed areas and forming touchy slabs.

40-70 cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and treeline elevations. Another two crust / surface hoar layers that formed in December are buried 60-90 cm below the surface. These layers produced sudden results in recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Weather Forecast

SATURDAY: 10 cm of snow Friday night then clearing and cooling throughout the day, strong west wind, alpine high temperatures around -12 C.

SUNDAY: Heavy snow starting Sunday morning with accumulations of 10-30 cm, moderate southwest wind, alpine high temperatures around -10 C.

MONDAY: Clearing with some isolated flurries, light wind, alpine high temperatures around -8 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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