Avalanche Forecast

Kootenay Boundary

Date issued

Mar 27, 2018 - 4:13 PM

Valid until

Mar 28, 2018 - 2:00 PM

Prepared by

mbender

Recent snow and wind have built slabs in recent days. Assess the bond between the new snow and the old snow surface before committing to bigger slopes.

Regular season
Tuesday - March 27, 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 - March 28, 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 - March 29, 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: Storm Slabs

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

Southwest wind combined with recent snowfall have formed fresh storm and wind slabs that sit on a mix of crusts, surface hoar and facets.

Travel and Terrain Advice
  • Use caution on steep slopes and convex rolls.
  • Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable storm snow.
  • Use caution in lee areas in the alpine and treeline. Storm snow and wind have formed touchy slabs.

Avalanche Summary

On Monday there were reports of numerous explosives triggered storm slab avalanches size 1.5-2 on northwest to northeast aspects in the alpine and tree line. Sunday there was a report of a natural size 2 wind slab and a skier triggered size 1 wind slab release. Both of these were on northeasterly aspects above 2000 m. Also on Sunday explosive control work produced numerous size 1.5-2 storm slab results all failing in the recent storm snow (25-40 cm deep) on north and northwest aspects above 2000 m.

Saturday we received reports of several remotely (from a distance) triggered and skier-triggered size 2 storm slab release that failed 40-50 cm deep on a mix of buried crusts, surface hoar and facets. Explosive control work also produced size 1.5-2 storm slab results running on a crust on southeast aspects from 1900 -2000 m. Read more here. And here.

Snowpack Summary

Around 30-40 cm of recent snow sits on a crust at all elevations on solar aspects and all aspects below 1900 m elevation. On northerly aspects at and above treeline the storm snow is burying a mix of large surface hoar and surface facets. Two other weak layers are present in the upper snowpack. A layer buried mid March is down 30 to 60cm is crust on solar aspects and surface hoar on high elevation north. A layer buried early March is 50 to 80cm below the surface and is similar in composition to those just described.

A few other persistent weak layers are buried in the mid and lower snowpack, but they have gone dormant and are unlikely to resurface until we move into a period with consecutive above-freezing nights later in the spring.

Weather Forecast

WEDNESDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -4 / Freezing level 1500 m.

THURSDAY: Mostly cloudy with isolated flurries / Light to moderate west wind / Alpine temperature -3 / Freezing level 1500 m.

FRIDAY: Mix of sun, cloud and isolated flurries / Light west wind / Alpine temperature -1 / Freezing level 1600m

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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