Avalanche Forecast

Kootenay Boundary

Date issued

Apr 22, 2018 - 3:47 PM

Valid until

Apr 23, 2018 - 2:00 PM

Prepared by

jlammers

Warming and solar radiation will drive the avalanche danger in the coming days. Watch for conditions that change throughout the day, and be cautious of overhead hazards.

Regular season
Sunday - April 22, 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 - 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.

Tuesday - April 24, 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: Loose Wet

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

Warming and solar radiation over the next few days are expected to trigger loose wet avalanches, especially in steep, sun-exposed terrain. Loose wet avalanches can be pushy and entrain mass quickly.

Travel and Terrain Advice
  • Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.
  • Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Avalanche Problem 2: Cornices

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

Warming and solar radiation may also cause large cornices to fail. Cornice failures may be dangerous by themselves, but they could also trigger a large avalanche on the slope below.

Travel and Terrain Advice
  • Avoid areas with overhead hazard.
  • Give cornices a wide berth when travelling on or below ridges.

Avalanche Problem 3: Wind Slabs

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

New snow and strong winds from Friday night and Saturday have formed wind slabs in upper elevation lee terrain. Although they're expected to gain strength quickly, I'd remain cautious around ridge crests and in gullies.

Travel and Terrain Advice
  • Be cautious as you transition into wind affected terrain.
  • Stay off recent wind loaded areas until the slope has had a chance to stabilize.

Avalanche Summary

No new avalanches have been reported although I'm sure there was a round of wind slab activity on Saturday in response to Friday night's snow and wind. I'm sure the new snow will be quick to settle and gain strength in the coming days. Loose wet avalanches and cornice falls are expected with warming and solar radiation forecast for this week. Although less likely, warming may also trigger unexpectedly deep and destructive slab avalanches failing on weaknesses which formed earlier in the season.

Snowpack Summary

New snow and wind from Friday night and Saturday formed relatively small wind slabs in upper elevation lee terrain. Depending on aspect and elevation, the new snow likely overlies a melt-freeze crust or settled storm snow from earlier in the week.

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; however, weaknesses deep within the snowpack have the potential to "wake-up" in isolated terrain with forecast warming and solar radiation.

Weather Forecast

A ridge of high pressure will develop for the forecast period bringing sunny skies and light ridgetop winds. The freezing level will hover around 2600m on Monday, 2800m on Tuesday and 3500m by Wednesday.

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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