Avalanche Forecast

Sea To Sky

Date issued

Jan 30, 2018 - 5:53 PM

Valid until

Jan 31, 2018 - 2:00 PM

Prepared by

cgarritty

Seek out sheltered terrain that holds evenly distributed new snow. Deep and unsupported wind deposits will remain unstable over the short term

Regular season
Tuesday - January 30, 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.

Wednesday - January 31, 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

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.

Thursday - February 1, 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.

Avalanche Problem 1: Storm Slabs

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

Heavy snowfall and intense winds created thick new storm slabs on the surface during the storm. The new snow's bond to the surface is improving, but slabs may remain reactive to human triggering in steep terrain and convex features.

Travel and Terrain Advice
  • Be aware of the potential for wide propagations due to the presence of hard windslabs.
  • Watch for slabs to trigger more easily in thin spots near deep wind-loaded deposits.

Avalanche Problem 2: Cornices

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

Recent heavy snowfall and high winds have created fragile new cornice growth.

Travel and Terrain Advice
  • Falling cornices may trigger large avalanches on the slopes below.
  • Give cornices a wide berth when travelling on or below ridges.

Avalanche Summary

Reports from Monday include observations of explosives control in the Whistler area producing numerous storm slab releases generally from Size 1.5 to 2.5 but with several Size 3.5 results and even one Size 4.

Saturday and Sunday's reports showed ski cutting as well as explosives control in the Whistler area producing numerous storm slab results from Size 1-2, as well as several Size 1.5 cornice releases.

A report from Friday detailed two explosive triggered Size 3.5 persistent slab avalanches. These avalanches started in the storm snow and then stepped down to the early January and even the mid-December crusts which resulted in very large avalanches running full path. They occurred on northwesterly aspects below rocky ridgetops between 1950-2200 m.

Snowpack Summary

Monday's continuing storm brought another 30-40 cm of new snow to the surface above about 1600 metres with depths that increase with elevation. At higher elevations, extreme southerly winds have been scouring the new snow from windward aspects and forming deep deposits and cornices in leeward terrain. Including the new snow, storm snow totals since mid-January have reached about 170 cm. Where they haven't been blown away by the wind, these accumulations sit on a crust from mid-January that shows good signs of bonding to the overlying snow.

Other deeper layers in the snowpack include a crust that was buried in early January (now 230-280 cm below the surface) and another crust which was buried in mid-December. Although explosive control work triggered storm slab avalanches that "stepped down" to both of these crusts last week, they are expected to have formed an improved bond with the overlying snow in most areas. With that said, a heavy trigger like a cornice release may still carry the risk of stepping down to deeper layers on isolated features where winds have created more variable snowpack depths and brought these layers closer to the surface.

Weather Forecast

Wednesday: Cloudy with scattered flurries bringing about 5 cm of new snow, continuing overnight. Light south winds. Freezing level to about 700 metres with alpine high temperatures of -7.

Thursday: Cloudy with continuing flurries and about 5 cm of new snow over the day. Increasing overnight. Light southwest winds, increasing overnight. Freezing level remaining near 700 metres with alpine high temperatures reaching -5.

Friday: Cloudy with continuing flurries and about 5 cm of new snow. Moderate southwest winds. Freezing level rising to 1500 metres with alpine high temperatures around -2.

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.