Avalanche Forecast

Lizard Range and Flathead

Date issued

Feb 17, 2018 - 4:46 PM

Valid until

Feb 18, 2018 - 2:00 PM

Prepared by

jmcbride

Intense snowfall beginning late Saturday afternoon and overnight, will increase avalanche danger on Sunday. Conservative terrain with no overhead hazard is a good choice.

Regular season
Saturday - February 17, 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.

Sunday - February 18, 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.

Monday - February 19, 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: Storm Slabs

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

Heavy loading from snow and wind will form widespread storm slabs. This new snow overlies a variety of old surfaces including hard wind scour, old wind slab and crusts and will likely be touchy.

Travel and Terrain Advice
  • Avoid avalanche terrain during periods of heavy loading from new snow and wind.
  • If triggered, storm slabs may step down to deeper layers resulting in large avalanches.
  • Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Avalanche Problem 2: Cornices

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

Cornices may be weak and have the potential to trigger large avalanches running long distances. Avoid lingering in runout zones below large corniced slopes, and stay well back from corniced ridge lines if traveling above them.

Travel and Terrain Advice
  • Avoid steep slopes below cornices.
  • Give cornices a wide berth when traveling on or below ridges.

Avalanche Problem 3: Deep Persistent Slabs

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

The potential for large avalanches running on buried weak layers exists. Wind loading, fragile cornices, and smaller avalanches are all possible triggers, as well as thin or rocky snowpack areas where human triggering may also be possible.

Travel and Terrain Advice
  • Avoid steep convexities or areas with a thin or variable snowpack.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.

Avalanche Summary

On Saturday explosive control work produced cornice failures up to size 2, triggering storm slabs on the slopes below.

Reports of natural and skier triggered storm slab and loose snow avalanches up to size 1.5 were reported during the storm on Friday, primarily in leeward areas in the alpine and at treeline.

On Thursday, natural storm slab and loose storm snow avalanches up to size 1.5 were reported to have occurred overnight with active loading during the storm, while explosive control work produced storm slab results up to size 1.5 on northerly slopes between 1700-1800 m.

Earlier in the week, explosive control work and ski cutting produced widespread storm slab results up to size 2.

Avalanche activity will increase as a result of Saturday's storm. Expect widespread storm slabs and new cornice growth from intense snowfall and wind-loading. Rapid loading also has the potential to wake up buried weak layers. Conservative terrain with no overhead hazard is recommended.

Snowpack Summary

About 40-60 cm of recent storm snow and wind have created storm slabs at upper elevations. This overlies old wind slabs on leeward slopes at treeline and above, as well as sun crusts on solar aspects and a mix of surface hoar and facets in sheltered areas near treeline.

Below 1700m, this new snow covers a rain crust that was buried on February 8th.

For the past month there has been regular avalanche activity on multiple weak layers in the mid and lower snowpack. A widespread weak layer from mid December composed of facets, crusts, and surface hoar is 120-160 cm deep. Also, a rain crust with sugary facets buried in late November is near the base of the snowpack.

The take home message is that several weak layers are still lurking in the snowpack and they deserve a lot of respect.

Weather Forecast

TONIGHT: Snow. Accumulation 10-20 cm. Ridge wind moderate to strong, northeast. Temperature -16. Freezing level valley bottom.

SUNDAY: Cloudy, light flurries. Accumulation trace. Ridge wind moderate to strong, northeast. Temperature -20. Freezing level valley bottom.

MONDAY: Mix of sun and cloud. Ridge wind light, northeast. Temperature -16. Freezing level valley bottom.

TUESDAY: Mix of sun and cloud. Ridge wind light, southwest. Temperature -12. Freezing level valley bottom.

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. Lizard Range and Flathead URL: http://www.avalanche.ca/api/forecasts/lizard-range.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.