Avalanche Forecast

South Coast Inland

Date issued

Feb 7, 2018 - 4:37 PM

Valid until

Feb 8, 2018 - 2:00 PM

Prepared by

swerner

Storm snow amounts will vary across the region. The Coquihalla will see higher amounts then the Duffy. Avoid avalanche terrain.

Regular season
Wednesday - February 7, 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

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.

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.

Thursday - February 8, 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

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.

Friday - February 9, 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.

Avalanche Problem 1: Storm Slabs

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

New storm snow accumulations will build touchy storm slabs, especially on leeward slopes where more wind loading occurs.

Travel and Terrain Advice
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Avalanche Problem 2: Cornices

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

Recent snowfall and strong winds have created large fragile cornices. Cornices are unpredictable and demand respect. Give them a wide berth from above and below. Know what is lurking above you.

Travel and Terrain Advice
  • Give cornices a wide berth when traveling on or below ridges
  • Falling cornices may trigger large avalanches on slopes below.

Avalanche Summary

On Tuesday, no new avalanche observations were reported from the northern part of the region (Duffy). In the south (Cascades) numerous glide avalanches up to size 3 were reported. Glide releases have a higher likelihood of failing when the ground cover is smooth bedrock or grass. Other avalanches to note from the south include wet slab avalanches up to size 2.5 with one reported as a size 3 from a steep southeast slope near 1700 m.

Natural avalanches are likely with forecast storm snow, rain at lower elevations and strong ridgetop winds.

Snowpack Summary

Recent snowfall totals are highly variable. In the south, up to 20 cm of new snow fell bringing the alpine totals up to 40 cm since the weekend. In the north, new snow totals are half that and rapidly decreasing below 1800m. This new snow sits on old wind slabs in alpine locations and has buried a crust at treeline. At lower treeline and below elevations, warm temperatures (and rain in many locations) have created heavy snow conditions.

This new snow adds to the 80-150 cm mid pack that sits above the mid- January crust, which generally shows signs of bonding. I would still remain suspect of this deeper layer, especially now, with additional load stressing the snowpack. Large fragile cornices could also act as a trigger on the slope below.

Weather Forecast

Thursday: 15-30 cm overnight Wednesday at upper elevations, with the higher accumulations being in the southern part of the region. 5-15 cm Thursday morning tapering off by early afternoon. Ridgetop winds strong from the southwest. Alpine temperatures near -5 with freezing levels 1300 m.

Friday: Mix of sun and cloud with alpine temperatures near -8 and freezing levels at valley bottom. Ridgetop winds light from the north.

Saturday: Mostly clear with no forecast snow. Alpine temperatures near -10 and ridgetop winds light from the northeast.

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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