Avalanche Forecast

Cariboos

Date issued

Jan 28, 2018 - 4:15 PM

Valid until

Jan 29, 2018 - 2:00 PM

Prepared by

mgrist

Warm storm coming! A widespread avalanche cycle is expected so it's best to avoid all avalanche terrain.

Regular season
Sunday - January 28, 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

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.

Monday - January 29, 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.

Tuesday - January 30, 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.

Avalanche Problem 1: Storm Slabs

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

Heavy snowfall and warming temperatures are a recipe for widespread avalanches. A storm slab could step down to a deeper weak layer, creating a surprisingly large avalanche.

Travel and Terrain Advice
  • Use caution in lee areas. Recent wind loading have created wind slabs.
  • Use conservative route selection. Choose moderate angled and supported terrain with low consequence.
  • Choose regroup spots that are out of avalanche terrain.

Avalanche Problem 2: Persistent Slabs

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

Several weak layers are buried in the snowpack, creating very large avalanches when triggered.

Travel and Terrain Advice
  • Avoid steep convexities or areas with a thin or variable snowpack.
  • Make conservative terrain choices, remembering that avalanches may be surprisingly large.

Avalanche Summary

Widespread recent avalanche activity was reported on Saturday near Allen Creek. Avalanches from Size 1 to 3 (many triggered by humans) were observed, especially on north east aspects between 1900m and 2600m. See this great MIN report for more information.

A widespread natural avalanche cycle is expected with Monday's storm, with the potential for some surprisingly large avalanches given how many persistent weak layers exist in the snowpack.

Snowpack Summary

The current snowpack is complex, with three active weak layers that professionals are monitoring. Recent storm snow has been blown around by winds to form wind slabs and cornices.

1) Down about 30-70 cm is a crust and/or surface hoar layer buried mid-January. The surface hoar is up to 10 mm in size, found at all elevation bands and very reactive on north east aspects between 1900-2600m.

2) Deeper in the snowpack, the early-January persistent weak layer is found 40 to 120 cm below the surface. It is composed of surface hoar on sheltered slopes and sun crust on steep solar aspects and found at all elevation bands. Snowpack tests show sudden fracture characters with easy to moderate loads and high propagation potential.

3) Another weak layer buried mid-December consisting of a facet/surface hoar/crust combination is buried 100 to 160 cm deep. It is most problematic at and below tree line.

A rain crust buried in November is 100 to 200 cm deep and is likely dormant for the time being.

See here for a good summary of snowpack test results.

Weather Forecast

Monday: 10-20 cm snow Sunday overnight into Monday and another 10-15 cm snow during the day. Moderate to strong south-westerly winds. Alpine temperature warming to near -3. Freezing level rising to 1500m by late afternoon.

Tuesday: Light snow (5cm possible). Light to moderate southerly winds. Alpine temperature -4.

Wednesday: Cloudy with isolated flurries. Light westerly winds. Alpine temperature near -5.

More information can be found in the Mountain Weather Forecast.

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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