Avalanche Forecast

Cariboos

Date issued

Feb 26, 2018 - 4:15 PM

Valid until

Feb 27, 2018 - 2:00 PM

Prepared by

jlammers

Extreme winds will drive the avalanche danger in many areas. The best and safest riding may be found in sheltered terrain.

Regular season
Monday - February 26, 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.

Tuesday - February 27, 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

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.

Wednesday - February 28, 2018
Alpine

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.

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

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.

Avalanche Problem 1: Wind Slabs

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

New snow and continued strong winds will create wind slabs in many areas in the alpine as well as open areas at lower elevations. If triggered wind slabs may "step down" to deeper layers including a weak interface buried mid-February.

Travel and Terrain Advice
  • Stay off recent wind loaded areas until the slope has had a chance to stabilize.
  • Be cautious as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.

Avalanche Summary

On Sunday several storm slab avalanches to size 2.5 occurred in response to new snow and wind. The avalanches failed on all aspects above 1800m.  Continued wind and snowfall will promote ongoing wind slab activity.

Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.

Snowpack Summary

About 20-40 cm of new snow now covers old surfaces which include of sugary facets, a sun crust on solar aspects and surface hoar on shaded, wind-sheltered slopes. I suspect strong winds will have redistributed much of the new snow into fresh wind slabs in exposed terrain.

30-60cm below the surface lies another interface, with similar character and distribution that was buried mid-February. This layer has been reactive in recent snowpack tests and is definitely worth keeping an eye on as the overlying slab gains thickness and cohesion.

Within the mid and lower snowpack are several persistent weak layers that are slowly beginning to show signs of improving but still remain suspect as low probability - high consequence avalanche problems. Two surface hoar/ crust layers buried in January are now 100-150 cm below the snow surface. At least one of these layers can be found on all aspects and elevations. Deeper in the snowpack (150 - 200 cm deep) is a facet/crust/surface hoar layer buried in December. Near the base of the snowpack is a crust/facet combo layer buried in late November.

Weather Forecast

Tuesday: 5-12cm of new snow / Extreme westerly winds / Alpine temperature of -15

Wednesday: Light flurries / Moderate to strong southwest winds / Alpine temperature of -8

Thursday: Light flurries / Light southerly winds / Alpine temperature of -5

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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