Avalanche Forecast

Northwest Inland

Date issued

Feb 4, 2018 - 6:31 PM

Valid until

Feb 5, 2018 - 2:00 PM

Prepared by

ghelgeson

Storm slabs are expected to remain sensitive to human triggering and a window of sun Monday afternoon could initiate a round of natural avalanche activity. Take a cautious approach and minimize your exposure to overhead avalanche terrain.

Regular season
Sunday - February 4, 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.

Monday - February 5, 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.

Tuesday - February 6, 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?

New snow and wind have likely formed touchy slabs, especially at higher elevations and in wind-affected terrain. There is potential for a brief window of strong sun Monday afternoon which could initiate a fresh round of storm slab avalanches.

Travel and Terrain Advice
  • Use conservative route selection, choose moderate angled and supported terrain with low consequence.
  • Avoid being on or under sun exposed slopes.
  • If triggered, storm slabs may step down to deeper layers resulting in large avalanches.

Avalanche Problem 2: Persistent Slabs

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

There is limited information about weak layers buried 30-80 cm below the surface. They produced a few large avalanches last week, and may remain sensitive to human triggering.

Travel and Terrain Advice
  • Avoid shallow or thick to thin snowpack areas where triggering a deeper layer is more likely.
  • Evaluate unsupported slopes critically.
  • Avoid lingering in runout zones.

Avalanche Summary

Reports have been limited. On Saturday a small storm slab was reportedly human triggered on an east facing aspect around 1000 m.

At the start of the storm on Wednesday and Thursday skiers triggered a few small slabs on steep convex rolls.

There are no recent reports of persistent slab avalanche activity, but some notable large avalanches occurred 5-8 days ago. This includes some large (size 2-3) natural persistent slab avalanches in the Howsons, and two large (size 2.5) remotely triggered avalanches north of Kispiox. We have no information from the Smithers area, but suspect a similar deeper weakness could exist there too. Activity on buried weak layers is most suspect during periods of heavy loading or rapid warming, hence it's time to be cautious.

Snowpack Summary

30-50 cm has already accumulated since Thursday. The snow has mostly fallen as low density powder, but may have settled in some areas that experience a brief period of warming on Friday. Westerly winds are likely blowing snow around in exposed terrain and forming touchy slabs.

40-70 cm of snow lies over a crust and/or weak feathery surface hoar layer buried in mid-January. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and treeline elevations. Another two crust / surface hoar layers that formed in December are buried 60-90 cm below the surface. These layers produced sudden results in recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

Weather Forecast

A strengthening ridge axis on Monday offers a brief lull in the action before the next system slams into the Northwest Coast on Tuesday before spilling into the Inland region on Wednesday.

MONDAY: Broken cloud cover in the morning, clearing in the afternoon, freezing level at valley bottom, light to moderate west/northwest wind, trace of snow possible.

TUESDAY: Overcast, freezing level at valley bottom, moderate to strong west/southwest wind, 1 to 5 cm of snow.

WEDNESDAY: Overcast, freezing level at valley bottom, moderate west/southwest wind, 5 to 15 cm of snow.

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. Northwest Inland URL: http://www.avalanche.ca/api/forecasts/northwest-inland.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.