Avalanche Forecast

South Coast Inland

Date issued

Apr 14, 2018 - 4:04 PM

Valid until

Apr 15, 2018 - 2:00 PM

Prepared by

mconlan

More snow forecasted in the south of the region Saturday night will keep the hazard at Considerable. Observe for the bond of the snow with the underlying crust before committing into avalanche terrain. Be particularly cautious if the sun comes out.

Regular season
Saturday - April 14, 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.

Sunday - April 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

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.

Monday - April 16, 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?

Recent snow has created slabs that are not bonding well to a crust. The slabs are particularly reactive in lee features, as the snow fell with strong south winds. Slab and loose avalanches will become more likely on south slopes if the sun comes out.

Travel and Terrain Advice
  • Avoid steep slopes when air temperatures are warm or the solar radiation is strong.
  • Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
  • Use ridges or ribs to avoid pockets of wind-loaded snow.

Avalanche Problem 2: Persistent Slabs

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

A weak layer buried 50 to 100 cm is still surprising people and producing large and destructive avalanches in the north of the region. Be particularly cautious around upper treeline and alpine terrain on shady aspects.

Travel and Terrain Advice
  • Pay attention to overhead hazards like cornices, which could trigger persistent slabs.
  • Avoid steep terrain or areas with a thin or variable snowpack.
  • Be aware of the potential for wide propagation due to the presence of buried weak layers.

Avalanche Summary

Numerous small wind slab avalanches were triggered by skiers on Friday, 20 to 35 cm deep and on northerly aspects in alpine terrain.  These were running within the recent storm snow on the melt-freeze crust. They were reported as easy to initiate, indicating that the bond between the new snow and the crust is poor.

Snowpack Summary

Around 30 to 50 cm of snow has fallen in the region between Thursday and Saturday.  This snow overlies a thick and hard melt-freeze crust.  On ridges, cornices are reported to be large and fragile. At low elevations below treeline, recent rain has created moist or wet snow conditions.

A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 50 to 100 cm. This layer is spotty in its distribution. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m.

The mid and lower snowpack are well-settled and strong.

Weather Forecast

SUNDAY: 10 to 20 cm snowfall in the south of the region early-morning, otherwise a mix of sun and cloud with late-afternoon snowfall, light northeast winds, alpine temperature -4 C, freezing level 1500 m.

MONDAY: Cloudy with snowfall, accumulation 15 to 20 cm, light west winds, alpine temperature -5 C, freezing level 1400 m.

TUESDAY: Mostly cloudy, light west winds, alpine temperature -5 C, freezing level 1500 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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