Avalanche Forecast

South Coast

Date issued

Jan 15, 2018 - 4:38 PM

Valid until

Jan 16, 2018 - 2:00 PM

Prepared by

jmcbride

Rain mixed with heavy snow and strong winds are expected during the forecast period. At upper elevations new snow will form touchy storm slabs.  At lower elevations, loose wet and wet slab avalanches will be a concern on rain-soaked, steep slopes.

Regular season
Monday - January 15, 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.

Tuesday - January 16, 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.

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

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.

Avalanche Problem 1: Storm Slabs

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

The combination of heavy wet snow and strong winds are the perfect recipe for widespread storm slab formation. At lower elevations where rain may be the predominant form of precipitation loose wet and wet slab avalanches will be the concern.

Travel and Terrain Advice
  • If triggered the storm slabs may step down to deeper layers resulting in large avalanches.
  • Use extra caution on slopes if the snow is moist or wet.
  • Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Avalanche Summary

Last Tuesday a skier was injured in a loose, wet avalanche on the North Shore mountains when the top 10-15 cm of wet snow released on the January 8th crust. On Saturday ski cutting produced loose wet sloughs in the top 5-10 cm of moist snow. On Friday explosive control produced a size 1 avalanche that released a 45 cm thick slab on a weak layer just above the January 7th crust.

Snowpack Summary

The upper snowpack consists of moist and wet snow and three prominent crusts (January 10th, January 8th an January 7th crusts) from recent warm weather and rain events.  The most notable layer is the January 7th rain crust, which is now buried 40-60 cm deep. The bond at this interface will likely gain strength over time; however, professionals are monitoring this layer as it has the potential to produce large avalanches in isolated terrain.

The snowpack depth at 1000 m is about 150 cm and many early season hazards are still present.

Weather Forecast

MONDAY NIGHT: Rain. Precipitation 8-12 mm. Ridge wind extreme, south. Temperature +4. Freezing level 1500 m.

TUESDAY: Mix of rain and snow. Accumulation 20-30 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1300 m.

WEDNESDAY: Rain mixed with snow. Accumulation 30-50 cm. Ridge wind extreme, south. Temperature +1. Freezing level 1600 m.

THURSDAY: Snow. Accumulation 35-45 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1200 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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