Avalanche Forecast

South Coast Inland

Date issued

Jan 28, 2018 - 5:07 PM

Valid until

Jan 29, 2018 - 2:00 PM

Prepared by

cgarritty

More warm, wet, and, windy weather in the forecast means that dangerous avalanche conditions will persist on Monday.

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

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.

Monday - January 29, 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.

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

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: Storm Slabs

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

New snow and wind will create another round of touchy storm slabs reactive to human triggers. Storm slab danger will likely increase with elevation, however rising temperatures and rain will promote loose wet avalanches at lower elevations.

Travel and Terrain Advice
  • Avoid avalanche terrain during periods of heavy loading from new snow and wind.
  • The new snow may require several days to settle and stabilize.
  • Use extra caution on slopes if the snow is moist or wet and avoid terrain traps like gullies.

Avalanche Problem 2: Deep Persistent Slabs

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

Intense loading of new snow may awaken deeply buried weak layers resulting in large, destructive avalanches.

Travel and Terrain Advice
  • Large triggers such as falling cornice or smaller avalanches may step-down to deeply buried crusts.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.

Avalanche Problem 3: Cornices

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

Large amounts of new snow and high winds will create tender cornices sensitive to human triggers.

Travel and Terrain Advice
  • Falling cornices may trigger large avalanches on slopes below.
  • Give cornices a wide berth when traveling on or below ridges

Avalanche Summary

Reports from Saturday showed recently formed storm slabs reactive to skier traffic and ski cutting, producing small (Size 1, 30-35 cm deep) storm slab and loose dry releases. Poor visibility was noted to be limiting observations.

On Thursday, two natural storm slab avalanches stepped-down to facets at the bottom of the snowpack and resulted in Size 3-3.5 avalanches. They occurred on north and south aspects between 2000 and 2250 m. The extended period of continuous loading of the snowpack may begin to reactivate deeply buried weak layers resulting in large and destructive avalanches running full path.

Snowpack Summary

Another 10 cm of new snow on Sunday morning brings recent storm totals to 90-120cm. Moderate to strong south winds have been redistributing each day's accumulations into dense storm slabs in lee and cross-loaded features at treeline and above.

90-120cm below the surface you'll likely find a few crusts that were buried during the first few weeks of January. Due to limited observations, not much is known about the current reactivity of these layers.

The lower snowpack includes the mid-December crust layer. The load of the new snow may tip the balance and reactivate this layer in isolated terrain - particularly in the north of the region where it has shown prolonged reactivity in snowpack tests.

Weather Forecast

Sunday night: Periods of snow bringing 20-30 cm of new snow. Heavy rain below about 1100 metres, possibly 1600 metres.

Monday: Continuing periods of snow bringing 10-25 cm of new snow to higher elevations. Rain below about 1600 metres. Strong to extreme southwest winds Freezing level to 2000 metres with alpine temperatures around 0.

Tuesday: Mainly cloudy with isolated flurries and a trace to 3 cm of new snow. Moderate to strong southwest winds. Freezing level to 1200 metres with alpine high temperatures around -4.

Wednesday: A mix of sun and cloud with isolated flurries and a trace of new snow. LIght west winds. Alpine high temperatures of -7.

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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