Avalanche Forecast

Cariboos

Date issued

Feb 1, 2018 - 5:33 PM

Valid until

Feb 2, 2018 - 2:00 PM

Prepared by

cgarritty

Another storm is bringing new snow, wind, and warming temperatures to the region. This is the same recipe that produced numerous very large persistent slab avalanches during the last storm.

Regular season
Thursday - February 1, 2018
Alpine

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.

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.

Friday - February 2, 2018
Alpine

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.

Treeline

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.

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.

Saturday - February 3, 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: Persistent Slabs

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

Several deeply buried weak layers are persisting in the snowpack and continue to produce very large avalanches, especially with heavy triggers. This is a time to carefully measure your exposure to avalanche terrain and to avoid overhead hazards.

Travel and Terrain Advice
  • Favour low angle terrain and choose low consequence slopes.
  • Carefully manage your exposure to overhead hazards while entering and leaving riding areas.

Avalanche Problem 2: Storm Slabs

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

New snow and strong west winds are expected to build fresh storm slabs over the day on Friday. Snowfall amounts are uncertain, but snow stability will be on a decreasing trend throughout the day.

Travel and Terrain Advice
  • Storm slabs may step down to deeply buried weak layers to produce very large avalanches.
  • Watch for the first touchy slabs to form in the lee of wind-exposed terrain features.

Avalanche Summary

Reports from Wednesday included more observations of widespread natural activity that took place over the previous few days. Numerous recent Size 2-3 releases were observed on all aspects at all elevations and several avalanches reached Size 4.  Subsequent explosives control yielded storm slab and wind slab releases from Size 2-2.5 and persistent slab results generally from Size 2.5-3. The early January persistent weak layer was named as the primary failure plane for persistent slab releases, although several larger releases stepped down to the mid-December layer. These observations illustrate that dangerous snowpack conditions continue to plague the region and will remain a serious concern for the foreseeable future.

On Tuesday natural avalanches to size 2.5 were reported on northwest facing slopes at 2200 m, running on the early January interface. A size 2.5 avalanche on a northeast facing slope at 1920 m resulted in a single fatality in Clemina Creek. More details available here.

A natural storm slab avalanche cycle occurred on Monday with heavy snow and temperatures up to +2 C in some tree line locations. See this MIN report for a good example of the avalanche activity.

Snowpack Summary

25-50 cm of storm snow fell between Sunday and Tuesday night. Temperatures reached -2 C at treeline in the south of the region (and +2 C near Barkerville) on Monday afternoon. The new snow sits on an unstable snowpack with three active weak layers we are monitoring:

1) Down about 40-80 cm is a crust and/or surface hoar layer that was buried in mid-January. The surface hoar is up to 10 mm in size, found at all elevation bands and has been very reactive on north through east aspects between 1900-2600 m.

2) Deeper in the snowpack, the early-January persistent weak layer is found 50 to 100 cm below the surface. This layer has been reported as the most active persistent weak layer during a recent natural avalanche cycle that took place in the region. It has also been the most reactive to recent explosives control.

3) Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 150 cm deep. It has been most problematic at and below tree line. Many avalanches that failed at shallower weak layers 'stepped down' to this interface during the recent avalanche cycle and in recent explosives control.

See here for some recent snowpack test results.

Weather Forecast

Friday: Cloudy with flurries bringing 10-20 cm of new snow, increasing overnight. Strong west winds, continuing overnight. Freezing level rising to 1400 metres with alpine high temperatures around -5.

Saturday: Cloudy with continuing flurries bringing 5-10 cm of new snow in the morning. Skies clearing over the day. Moderate to strong northwest winds. Freezing level returning to the surface with alpine high temperatures of -12.

Sunday: Increasing cloud with isolated flurries and a trace of new snow. Light variable winds. Alpine high temperatures of -10.

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. Cariboos URL: http://www.avalanche.ca/api/forecasts/cariboos.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.