Avalanche Forecast

South Coast Inland

Date issued

Jan 17, 2018 - 4:36 PM

Valid until

Jan 18, 2018 - 2:00 PM

Prepared by

jmcbride

A wet and wild winter storm system with heavy snow, strong winds and mild temperatures is increasing the avalanche hazard. Travel in avalanche terrain is not recommend until the new snow has had a chance to settle and bond to the old surface.

Regular season
Wednesday - January 17, 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.

Thursday - January 18, 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.

Friday - January 19, 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: Storm Slabs

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

New snow and strong winds will build touchy storm slabs particulary at upper treeline and alpine elevations. In northern parts of the region it may still be possible for a surface release to step down to a deeper layer.

Travel and Terrain Advice
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Minimize exposure during periods of heavy loading from new snow and wind or rain.

Avalanche Problem 2: Loose Wet

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

It may be possible to trigger a loose wet slide in steep, unsupported or convex terrain where rain has soaked the upper snowpack.

Travel and Terrain Advice
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.
  • Use extra caution on solar slopes or if the snow is moist or wet.

Avalanche Summary

Reports from Tuesday indicate that the new snow had formed thin wind slabs that were reactive to skier triggers but had little mass or consequence. Expect this to change as new snow amounts accumulate with the approaching storm.

On Sunday there was a report of a skier triggered size 2.5 slab avalanche in the northern part of the region that initiated as a 30 cm thick wind slab then stepped down to approximately 70 cm thick (likely the mid December layer) on a north-east aspect at 2050 m.

Snowpack Summary

A new snow (up to 25 cm in the northern areas and about 5 cm in southern parts) has buried the most recent, January 15th crust. This crust exists on almost all aspects and elevations with the exception of northerly aspects above 1850 m where the snow surface remained dry during the alpine inversion event on the weekend.

Below the January 15th crust about 30-50 cm of snow overlies a 1 cm thick crust that was buried on January 6th which exists up to about 2000m.

Mid and lower snowpack layers including the mid December and late November crust layers have produced moderate to hard, sudden results in snowpack tests in the northern part of the region last week and may be a concern for step-down potential.

Weather Forecast

TONIGHT: Snow. Accumulation 15-25 cm. Ridge wind extreme, southwest. Temperature near 0. Freezing level lowering to 1300 m.

THURSDAY: Snow. Accumulation 10-20 cm. Ridge wind strong, southwest. Temperature -2. Freezing level 1300 m.

FRIDAY: Cloudy, flurries. Accumulation 2-8 cm. Ridge wind moderate, southwest. Temperature -2. Freezing level 1000 m.

SATURDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate southwest. Temperature -2. Freezing level 1000 m.

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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