Avalanche Forecast

Cariboos

Date issued

Mar 10, 2018 - 4:32 PM

Valid until

Mar 11, 2018 - 3:00 PM

Prepared by

cgarritty

Solid overnight cooling means that surface instabilities remain the primary concern in the Cariboos. This may change in the coming days.

Check out the Forecasters' Blog for more details: http://www.avalanche.ca/blogs/2018-03-09-first-big-warm-up

Regular season
Saturday - March 10, 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

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.

Sunday - March 11, 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 - March 12, 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: Wind Slabs

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

Wind slabs formed on all aspects during the recent storm and they may remain reactive on Sunday. Extra caution is needed on solar aspects where sunshine could act as a natural trigger and  buried sun crust as a sliding layer.

Travel and Terrain Advice
  • If triggered, large wind slabs may step down to deeper layers and result in very large avalanches.
  • Pay attention to cornices and give them a wide berth when travelling on or below ridges.

Avalanche Problem 2: Loose Wet

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

Sun on new snow is likely to lead to loose moist avalanches which could run surprisingly far. Large loose avalanches may also have potential to step down to deeply buried weak layers.

Travel and Terrain Advice
  • Be cautious of sluffing in steep terrain, particularly where the debris flows into terrain traps.
  • Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.
  • Choose regroup spots carefully, thinking about what is above you.

Avalanche Summary

Reports from Friday included numerous observations of loose dry avalanches reaching size 2. These occurred in steeper terrain on all aspects. Numerous recent wind slab releases were also observed to have run naturally up to size 2.5 on steeper north aspects.

Thursday's reports included one observation of an older size 2.5 natural wind slab release in the south of the region. This avalanche occurred on a 40 degree southwest slope in the alpine and had a depth of 60 cm.

On Wednesday, a chunk of falling ice triggered a size 2.5 avalanche. On Tuesday, a few large cornice falls were reported, without releasing large avalanches on slopes below.

Avalanche activity is expected to increase as we move into a period of intense sun and prolonged warming. Predictable loose wet avalanches from steep, sunny terrain should be easy to manage. A trickier problem will gradually emerge as warmth penetrates into the snowpack to tickle deeper persistent weak layers that have lately been dormant in the Cariboos. The next few days will be a time to avoid exposure to large sunny features and keep well away from corniced slopes.

Snowpack Summary

Thursday's storm brought 20-30 cm of new snow by Friday morning. This new snow overlies well-settled storm snow from regular snowfalls over the past couple of weeks. Although several layers of sun crust can be found within this storm snow on solar aspects, recent snowpack tests have not been producing concerning results in the upper snowpack.

Persistent weak layers from early January and mid-December are still being reported by local operators. They are generally considered dormant, but could wake up with forecast warming, a surface avalanche stepping down, a cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets. A weak layer of facets also lingers at the base of the snowpack.

Weather Forecast

Sunday: Mainly sunny. Light south winds. Freezing level rising to 1800 metres with alpine high temperatures of -2.

Monday: Sunny. Light southeast winds. Freezing level rising to 2500 metres with alpine high temperatures around 0 to +1.

Tuesday: A mix of sun and cloud, becoming cloudier. Light southeast winds, increasing over the day. Freezing level to 2500 metres with alpine high temperatures of +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.

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