Avalanche Forecast

Northwest Coastal

Date issued

Apr 23, 2018 - 4:01 PM

Valid until

Apr 24, 2018 - 2:00 PM

Prepared by

jsmith

Sunshine and rising temperatures will elevate the avalanche danger throughout the week. Be aware of changing conditions throughout the day and avoid overhead hazards.


This is our final daily forecast for the season which will expire on April 25th.

Regular season
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

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 - April 25, 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.

Thursday - April 26, 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?

Sunshine and warming temperatures will increase the loose wet avalanche activity throughout the week.

Travel and Terrain Advice
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.
  • Watch for signs that the snow is heating up such as pin-wheeling or the surface snow becoming moist.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

Avalanche Problem 2: Cornices

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

Sunshine and warming temperatures will increase the likelihood of cornice failures.

Travel and Terrain Advice
  • Falling cornices may trigger persistent weak layers deeper in the snowpack.
  • Cornices become weak with daytime heating. Give them a wide berth both from above and below.

Avalanche Summary

Several very large deep persistent slab avalanches(size 3-4) which were triggered by cornice failures and several natural wind slabs up to size 2.5 were reported near Bear Pass on Saturday. Avalanche reports have been limited due to very few information sources this time of year. If you have been out, please post your observations on the Mountain Information Network. (MIN)

Snowpack Summary

Cornices are large and when they fail there is the potential to trigger large avalanches on deeply buried weak layers. Lingering wind slabs may be reactive to human triggers on leeward slopes below ridgetops.

In the south of the region, two layers of surface hoar are buried approximately 70-100 cm deep and most prominent on north to east aspects. Further north, these layers are around 40 cm deep. Below these March layers the mid-pack is generally well-settled and strong.

In the far north of the region there are weak sugary facets near the bottom of the snowpack.

Weather Forecast

TUESDAY: Mix of sun and cloud. Light to moderate west wind. Alpine temperature +4. Freezing level 1500 m.

WEDNESDAY: Sunny. Light west wind. Alpine temperature +9. Freezing level rapidly rising to 3200 m.

THURSDAY: Sunny. Light southwest wind. Alpine temperature +12. Freezing level 3000 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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