Avalanche Forecast

Northwest Coastal

Date issued

Mar 11, 2018 - 3:45 PM

Valid until

Mar 12, 2018 - 2:00 PM

Prepared by

mconlan

Sustained winds have produced new wind slabs in lee features. Increasing freezing levels and sunny skies are intensely warming the snowpack. The best riding will be in areas sheltered from the wind effect and sun, without any overhead exposure.

Regular season
Sunday - March 11, 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.

Monday - March 12, 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.

Tuesday - March 13, 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.

Avalanche Problem 1: Wind Slabs

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

Strong southerly winds have redistributed the recent storm snow and formed touchy wind slabs in lee features. These slabs overly a weak surface hoar layer in parts of the region, allowing for wide propagation and fast-moving avalanches.

Travel and Terrain Advice
  • Approach lee and cross-loaded slopes with caution.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Avalanche Problem 2: Loose Wet

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

Rising freezing levels and sunny skies will allow for intense warming of the snowpack on solar aspects. Pay close attention to the effects of the sun on avalanche terrain and avoid overhead exposure.

Travel and Terrain Advice
  • Use extra caution on solar slopes or if the snow is moist or wet.
  • Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

Avalanche Summary

Wind slabs were reactive to skier traffic and natural activity on Saturday. Numerous size 1 to 2 avalanches were reported, generally 10 to 30 cm deep and at treeline and alpine elevations on northerly aspects. Many of these avalanches travelled fast and far when sitting on weak surface hoar. Loose snow was also noted in steep terrain features.

Snowpack Summary

Sustained southerly winds have redistributed the 20 cm of new snow and produced wind slabs in lee features. This overlies a sun crust on solar aspects and 5 to 20 mm surface hoar on sheltered, shady aspects at all elevation bands. Expect to find a melt-freeze crust early mornings and moist snow with warming below around 1500 m.

Beneath this, expect layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm below the surface from mid- and late-February. A surface hoar and crust layer from January is buried around 150 to 200 cm.

Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north.

Weather Forecast

MONDAY: Partly cloudy, moderate southerly winds, alpine temperature 2 C, freezing level 2000 m.

TUESDAY: Mostly sunny, light to moderate southeasterly winds, alpine temperature 4 C, freezing level 2200 m.

WEDNESDAY: Cloudy with light snowfall, accumulation 5 cm, light southerly winds, alpine temperature 0 C, freezing level 1400 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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