Date issued

Apr 20, 2018 - 4:00 PM

Valid until

Apr 21, 2018 - 4:00 PM

Prepared by

jasper snow safety

Avoid all slope with cornices overhead as there is recent evidence of them falling recently. This is considered a large trigger on the slope below.

Regular season
Saturday - April 21, 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.

Sunday - April 22, 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.

Monday - April 23, 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.

Avalanche Problem 1: Wind Slabs

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

Although mostly thin some wind slabs are up to 40cm thick in alpine terrain. Solar radiation and cornice collapses can trigger these events. Once triggered the potential to trigger deeper weaknesses exists resulting in larger avalanches.

Travel and Terrain Advice
  • Use caution in lee areas. Recent wind loading has created wind slabs.
  • Use caution on open slopes and convex rolls

Avalanche Problem 2: Loose Wet

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

Pay close attention to the effect of solar radiation and daytime warming. Point release from rocks and cliff terrain can trigger isothermal snow below. This will be of most concern in the late afternoon.

Travel and Terrain Advice
  • Avoid terrain traps, such as gullies, where the consequences of a small avalanche could be serious.
  • Use extra caution on solar slopes or if the snow is moist or wet.

Avalanche Problem 3: Persistent Slabs

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

These events require a significant force to trigger them such as a large cornice failure or avalanche debris from above. Once triggered they can be very large and run far into the valley below. Many slopes have already been triggered.

Travel and Terrain Advice
  • Pay attention to overhead hazards like cornices which could easily trigger deep slabs.
  • Avoid shallow snowpack areas where triggering is more likely.

Avalanche Summary

No patrol Friday. In the past 48hrs persistent slab avalanches up to size 3.5 have occurred from alpine terrain. They are size 2-2.5 and are are being triggered by cornice failures or small windslab avalanches stepping down to these deeper layers. With freezing levels reaching treeline expect some loose avalanches on South to West facing slopes.

Snowpack Summary

Windslabs are up to 40cm deep. Sun or temperature crusts extend to treeline and continued into the alpine on southerly slopes. Persistent slabs can be found on most aspects at treeline and above. These have been most reactive recently to large triggers like cornice failures. Below 1,900m the snowpack is isothermal.

Weather Forecast

Saturday will be cloudy, sun and flurries, 5cm of snow, -2 C, West winds 25-50km/hr, and freezing level 1900m. Sunday will be a mix of sun and cloud, -10 to -5, West winds 15-45km/hr, and freezing level 1600m. Monday will be sun and cloud, no precipitation,  -9 to plus 1 C, light winds, and 2400m freezing level.

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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