Avalanche Forecast

Northwest Coastal

Date issued

Jan 15, 2018 - 4:25 PM

Valid until

Jan 16, 2018 - 2:00 PM

Prepared by

simonhorton

Reactive slabs will develop throughout the week as snow accumulates. Be prepared to back off if slopes are getting loaded by fresh snow or wind.

Regular season
Monday - January 15, 2018
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.

Tuesday - January 16, 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

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.

Wednesday - January 17, 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: Wind Slabs

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

Strong southerly winds have blown recent snow into fresh wind slabs in lee terrain. Older, more stubborn wind slabs from recent outflow winds may still be reactive around ridge crests and on cross-loaded features at lower elevations.

Travel and Terrain Advice
  • Be increasingly cautious as you transition into wind affected terrain.
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Avalanche Problem 2: Persistent Slabs

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

Weak layers buried 60-80 cm below the surface may be reactive in thin snowpack areas or triggered with heavy loads such as a smaller avalanche.

Travel and Terrain Advice
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
  • Avoid convexities or areas with a thin or variable snowpack.

Avalanche Summary

Warm alpine temperatures over the weekend caused a natural cycle of large wet loose avalanches (up to size 2.5) on steep solar aspects throughout the region. Some smaller wind slab avalanches were reported in cross-loaded gullies around Bear Pass.

Snowpack Summary

Surface snow is well settled after a weekend of warm alpine temperatures. Wind slabs are lingering on a range of aspects after strong southerly winds on the weekend and outflow winds last week.

Below the most recent precipitation, up to 40 cm recent snow overlies several layers of interest in the upper snowpack. These include crusts, surface hoar and facets. A hard crust with associated facets from mid-December sits deeper in the snowpack, about 60 cm down. These layers have been reactive in recent snowpack tests and could potentially be triggered to release large avalanches.

The lower snowpack is generally strong, with the exception of areas around Stewart and further north where a basal crust and facets exist.

Weather Forecast

TUESDAY: 5-15 cm of new snow, strong south winds, freezing level dropping to 700 m.

WEDNESDAY: More flurries with 10-20 cm of new snow, strong south winds, freezing level steady at 700 m.

THURSDAY: Another 10-20 cm of new snow, strong south winds, freezing level steady at 700 m.

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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