Avalanche Forecast

Northwest Coastal

Date issued

Apr 10, 2018 - 4:07 PM

Valid until

Apr 11, 2018 - 2:00 PM

Prepared by

jmcbride

New snow and strong winds will form storm slabs at upper elevations, while lower elevations are likely to receive rain. Be aware of conditions that change with elevation as you transition from wet to new snow.

Regular season
Tuesday - April 10, 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 - April 11, 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

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.

Thursday - April 12, 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.

Avalanche Problem 1: Storm Slabs

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

New snow may bond poorly to an underlying crust. Watch for fresh storm slabs in leeward areas near ridge crests and convex features, as well as loose snow releases in steep terrain.

Travel and Terrain Advice
  • Use caution in lee areas in the alpine and treeline. Storm snow may form touchy slabs.
  • Be cautious of sluffing in steep terrain, especially above cliffs or terrain traps.

Avalanche Problem 2: Loose Wet

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

Sun and daytime warming are factors to keep in mind. Watch for wet snow on sunny aspects and lower elevation slopes, especially in the afternoon.

Travel and Terrain Advice
  • Use extra caution on slopes if the snow is moist or wet.

Avalanche Summary

Northern parts of the region reported that; warming on Sunday and Monday produced a natural, loose, wet avalanche cycle up to size 2 on all aspects up treeline and in steep alpine terrain.

Last week, the Shames area saw a widespread natural cycle up to size 3 on solar aspects as a result of Friday's storm. See recent MIN report. While further north only isolated wind slab and loose, wet activity was reported. Read MIN report.

On Thursday northern parts of the region saw a widespread natural avalanche cycle triggered by strong to extreme wind loading event in the alpine. There was also a report of an icefall triggered size 2.5 slab avalanche that failed on the mid-March interface, northwest of Meziadin Lake.

Snowpack Summary

Rain and warming to ridge top elevations have created wet or moist snow in the top 20-30 cm of the snowpack that is likely to be covered by a light dusting of new snow by Wednesday morning. Only high alpine, north aspects (above 2000 m) may still be harboring dry snow.

In the south of the region, two layers of surface hoar are buried approximately 70-100 cm deep. The layers are most prominent on north to east aspects and were buried early-March and mid-March. In the north of the region, these layers are around 40 cm deep.

Bellow these March layers the mid-pack is generally well-settled and strong. However, shallower parts of the region, such as the far north, have weak sugary facets near the bottom of the snowpack.

Weather Forecast

TONIGHT: Flurries. Accumulation 10-15 cm. Ridge wind strong to extreme, south. Alpine temperature near -2. Freezing level lowering to 800 m.

WEDNESDAY: Mostly cloudy, flurries. Accumulation 5-10 cm. Ridge wind strong to extreme, southeast. Alpine temperature near -2. Freezing level 1200 m. Snow beginning in the evening.

THURSDAY: Mix of sun and cloud, flurries ending. Accumulation 5-10 cm. Ridge wind moderate, south. Alpine temperature near -5. Freezing level 1100 m.

FRIDAY: Mostly cloudy, snow. Accumulation 10-20 cm. Ridge wind moderate, south. Alpine temperature near -5. Freezing level 1100 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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