Avalanche Forecast

Lizard Range and Flathead

Date issued

Feb 2, 2018 - 5:44 PM

Valid until

Feb 3, 2018 - 2:00 PM

Prepared by

shorton

More snow and strong wind will result in large natural avalanches. Stick to simple terrain and avoid overhead hazards.

Regular season
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

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 4, 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.

Avalanche Problem 1: Storm Slabs

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

Storm slabs have already been active and are growing with the incoming snow and wind, especially at higher elevations. Weather forecasts are handling the situation poorly, so some areas may have extra thick and touchy storm slabs.

Travel and Terrain Advice
  • Avoid avalanche terrain during periods of heavy loading from new snow and wind.
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Stick to simple terrain and be aware of what is above you at all times.

Avalanche Problem 2: Deep Persistent Slabs

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

Large avalanches have been running on deep weak layers. Additional loading and fragile cornices are likely triggers.

Travel and Terrain Advice
  • Avoid areas with overhead hazard.
  • Extra caution needed around cornices with current conditions.

Avalanche Summary

On Friday, storm snow was very reactive to ski cutting and explosives, producing many 20-40 cm thick storm slabs. Poor visibility obstructed alpine views, but natural activity was likely at higher elevations.

There was a brief break in persistent slab avalanche activity this week. However, on Monday and Tuesday, many large (size 2-3) avalanches were triggered naturally and with explosives. Most of the natural avalanches were triggered by cornices falling and releasing slabs on the December and November layers, producing 150-250 cm thick crowns. This type of activity has been occurring on a regular basis for the past month, and the incoming storm has potential to produce more of the same.

Snowpack Summary

Expect waves of fresh snow over the next few days as storm snow accumulates. Stay aware of the condition of the new snow. Mostly low density powder is expected, but could become heavy if it warms up. Also expect slab development in wind affected areas. The new snow sits above a breakable crust up to 1700 m.

For the past month we have seen regular avalanche activity on multiple deep weak layers. A layer buried mid-January is composed of surface hoar on sheltered aspects (especially prominent from 1400-1900 m) and a sun crust on solar aspects and is now 60-80 cm deep. Another surface hoar layer from early-January is buried 90-110 cm deep. A widespread weak layer from mid-December composed of facets, crusts, and surface hoar is 120-160 cm deep. Finally, a rain crust with sugary facets buried in late-November is near the bottom of the snowpack and up to 200-250 cm deep.

The bottom line is the snowpack structure in this region is weak. Human triggering is most likely on the shallower weak layers, but any avalanche has the potential to step down to deeper layers and become much larger.

Weather Forecast

Clashing fronts make for difficult forecasting the next few days. A Pacific warm front and an Arctic cold front are converging over the Rockies, creating the potential for some surprise accumulations of low density snow. Timing, location, and intensity are highly uncertain and so are the estimated snowfall amounts.

SATURDAY: Flurries starting Friday afternoon will deliver a moderate amount overnight and continue throughout the day (10-25 cm?), strong northwest wind, freezing level 1200 m in the morning then dropping with alpine high temperatures around -4 C.

SUNDAY: Snow resuming Sunday morning with heavy accumulations possible throughout the day and into Sunday evening (20-50 cm?), strong west wind, alpine high temperatures around -4 C.

MONDAY: Flurries easing off over the day, decreasing wind, alpine high temperatures around -12 C.

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.