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Avalanche Forecast

Apr 17th, 2015–Apr 18th, 2015
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Sea To Sky.

Solar radiation and rising temperatures will destabilize the snowpack and avalanche hazard can rise quickly. Check out the new blog post for this region: www.avalanche.ca/blogs/VTAw_CcAAIUPxFdk/south-coast-problems

Confidence

Fair - Due to the number of field observations

Weather Forecast

A dominating high pressure ridge is building over Southern BC. This will bring summer-like temperatures through the weekend with alpine temps rising to 12 degrees!  Saturday and Sunday will be mostly sunny skies with few clouds. Alpine temperatures rising to 8-12 degrees and freezing levels near 2900 m. Ridgetop winds will be light from the WNW. By late Monday, the ridge starts to break down allowing a more seasonally westerly flow.

Avalanche Summary

On Thursday, numerous solar triggered natural loose wet avalanches up to size 1 were reported. A natural cornice failure size 1 also occurred and did not pull a slab from the slope below. With warming and periods of intense solar radiation avalanche danger will rise, solar triggered slab avalanches, failing cornices and loose wet avalanches will likely continue. Be aware of rapidly changing conditions.

Snowpack Summary

Upper elevations have received 25-40 cm of recent storm snow. The new snow sits on the April 10th persistent weak interface including crusts, facets and spotty surface hoar on high, northerly aspects. This interface has shown a poor bond and has been reactive naturally and to human triggers. Moderate to strong south west winds has redistributed the recent storm snow into wind slabs on leeward slopes and behind terrain features. The mid-March pwl is down 100-150 cm and has been producing hard, resistant results in snowpack tests and has sat dormant. There is a low probability of triggering this layer, however; if it is triggered the consequence would be high. Large looming cornices may become weak with solar radiation and daytime warming. If a cornice fails it could trigger a large avalanche from the slope below.

Avalanche Problems

Persistent Slabs

Two persistent weak layers sit in the upper snowpack. One is down 25-50 cm and has been recently reactive naturally, and to human triggers. The second one sits 100-150 cm down and may re-awaken with warming, cornice fall and step down avalanches.
Be aware of the potential for large, deep avalanches due to the presence of a buried crust/facet layer.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 5

Cornices

Recent cornice growth has been observed and large cornices are expected to become weak with solar radiation and daytime warming. Cornices could trigger large slab avalanches.
Pay attention to overhead hazards like cornices.>Give cornices a wide berth when travelling on or below ridges.>

Aspects: North, North East, East, South East, South.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 3 - 5

Loose Wet

Solar radiation and rising freezing levels will deteriorate the snowpack quickly. Travel on sunny slopes early, and watch for signs of instabilities like avalanches, moist surface snow and snowballing.
Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3