Avalanche Forecast

Kootenay Boundary

Date issued

Apr 19, 2018 - 4:18 PM

Valid until

Apr 20, 2018 - 2:00 PM

Prepared by

jmcbride

High overnight freezing levels combined with continued warm temperatures and sunny skies on Friday will increase the likelihood of loose, wet avalanche activity.  These releases can start small and gain mass quickly becoming a big problem.

Regular season
Thursday - April 19, 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 - April 20, 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.

Saturday - April 21, 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: Loose Wet

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

Sunny skies and warming air temperatures will rapidly weaken the snow surface and increase the likelihood of triggering loose wet avalanches. Expect natural avalanches on steep slopes, particularly south aspects under sunny skies.

Travel and Terrain Advice
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
  • If triggered the loose wet sluffs may step down to deeper layers resulting in large avalanches.
  • Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Avalanche Summary

Wednesday numerous natural loose, wet avalanches (size 1-1.5) were observed on solar (southeast, south, and west) aspects in the southeastern part of the region.

On Tuesday there was a report of a skier-triggered storm slab size 1.5 on a north aspect at treeline north of Rossland that failed on a crust. Read MIN report here.

On Monday, loose wet avalanches were triggered naturally and by explosives. They were large (size 2 to 2.5) and on all aspects between 1700 m and 2100 m.

Snowpack Summary

Snow and warm temperatures on Thursday have likely moistened the 35 to 60 cm of storm snow that fell earlier in the week.  This snow sits on a melt-freeze crust that formed following rain and warm temperatures on Sunday.

Numerous other melt-freeze crusts exist in the upper snowpack from rain, sun, and warming during the spring season.

The mid and lower snowpack are generally well-settled and strong.

At lower elevations below treeline, a spring snowpack exists.

Weather Forecast

TONIGHT: Mostly clear. Ridge wind light, southwest. Alpine temperature near +1. Freezing level 2200 m.

FRIDAY: Mostly sunny. Increasing cloud and rain overnight. Precipitation up to 5 mm. Ridge wind light southwest. Alpine temperature near +2. Freezing level 2200 m.

SATURDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate to strong, southwest. Alpine temperature near -2. Freezing level 1700 m.

SUNDAY: Mix of sun and cloud. Ridge wind light, northwest. Alpine temperature near 0. Freezing level 2000 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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