Avalanche Forecast

Sea To Sky

Date issued

Apr 14, 2018 - 4:28 PM

Valid until

Apr 15, 2018 - 2:00 PM

Prepared by

mconlan

Slabs have been reactive to human traffic, particularly in lee terrain features. The likelihood of triggering avalanches will increase if the sun comes out, so best to avoid southerly slopes under intense sun.

Regular season
Saturday - April 14, 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

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.

Sunday - April 15, 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.

Monday - April 16, 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: Wind Slabs

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

Recent snow has created new slabs, which are up to 1 m thick in lee features due to strong south winds. Precipitation fell as rain at low elevations, so expect wet snow. Loose wet avalanches are possible if the sun comes out.

Travel and Terrain Advice
  • Avoid steep slopes when air temperatures are warm or the solar radiation is strong.
  • Use ridges or ribs to avoid pockets of wind-loaded snow.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

Avalanche Problem 2: Persistent Slabs

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

A weak layer buried 60 to 140 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.

Travel and Terrain Advice
  • Pay attention to overhead hazards like cornices, which could trigger persistent slabs.
  • Be aware of the potential for wide propagation due to the presence of buried weak layers.
  • Avoid steep terrain or areas with a thin or variable snowpack.

Avalanche Summary

On Friday, many small to large (size 1 to 2) storm and wind slabs were explosively controlled and ski cut across the region.  They were generally at treeline and alpine terrain with slab depths of 20 to 50 cm.  Cornices were also reactive to explosives but were generally small.

Snowpack Summary

30 to 40 cm of new snow between Thursday and Saturday has been redistributed by strong south winds, forming reactive storm and wind slabs up to 1 m deep.  Ridgelines are heavily corniced and if they fail they could trigger slabs on slopes below.

A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 140 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.

Below this, the snowpack is well-settled and strong.

Weather Forecast

SUNDAY: A mix of sun and cloud, light northeast winds, alpine temperature -4 C, freezing level 1500 m.

MONDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light west winds, alpine temperature -5 C, freezing level 1400 m.

TUESDAY: Mostly cloudy, light west winds, alpine temperature -5 C, freezing level 1400 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.

Avalanche Forecasts in your Inbox

Avalanche Canada has switched to an RSS feed for its daily forecasts. This is a much more flexible method that allows automatic delivery to your email inbox, or to an RSS reader of your choice.

What are RSS feeds?

RSS (Really Simple Syndication) is a popular standardized file format allowing up-to-date delivery of web-based content. RSS feeds enable you to receive content updates from websites, delivered to your email through an RSS aggregator (such as blogtrottr.com) or viewed through applications called RSS readers (such as feedly.com).

Set up an RSS feed for your email:

Select a RSS aggregator

  1. Sea To Sky URL: http://www.avalanche.ca/api/forecasts/sea-to-sky.rss
  2. Copy the url and paste it into the appropriate field of your RSS aggregator.
  3. Fill in your email address.
  4. Voila! Watch the Avalanche Canada forecast roll into your inbox.

Forecast Disclaimer

Avalanche Canada's Public Avalanche Bulletin, and other information and services provided by Avalanche Canada, are intended for personal and recreational purposes only.

**THIS INFORMATION IS PROVIDED "AS IS" AND IN NO EVENT SHALL THE PROVIDERS BE LIABLE FOR ANY DAMAGES, INCLUDING, WITHOUT LIMITATION, DAMAGES RESULTING FROM DISCOMFORT, INJURY, OR DEATH, CLAIMS BY THIRD PARTIES OR FOR OTHER SIMILAR COSTS, OR ANY SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, ARISING OUT OF THE USE OF THE INFORMATION.**

The user acknowledges that it is impossible to accurately predict natural events such as avalanches in every instance, and uses the data in this bulletin with this always foremost in mind. The accuracy or reliability of the data is not guaranteed or warranted in any way and the Providers disclaim liability of any kind whatsoever, including, without limitation, liability for quality, performance, merchantability and fitness for a particular purpose arising out of the use, or inability to use the data.