Avalanche Forecast

Issued: Apr 16th, 2015 9:30AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Persistent Slabs, Cornices and Loose Wet.

swerner, Avalanche Canada

Sea To Sky.

Solar radiation and rising temperatures will destabilize the snowpack and avalanche hazard can rise quickly. Watch overhead hazards like cornice fall. Loose wet sluffing and solar triggered slab avalanches.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A pacific front hits the North and Central coast Thursday evening and then slides south towards the South Coast. Confidence is poor with determining how far this storm will track south. Lingering cloud, sunshine and periods of convective snowfall may occur on Friday. Ridgetop winds will be light from the SW and freezing levels near 2200 m. Friday evening a warm ridge builds over the province bringing sunny and dry conditions into early next week. Saturday and Sunday freezing levels will be steady near 2700 m with intense solar radiation and ridgetop winds remaining light.

Avalanche Summary

On Wednesday, solar triggered natural loose wet avalanches up to size 1 were reported. On Tuesday, a skier triggered size 1 storm slab avalanche failed on a NE aspect around 2100 m. The skier was partially buried with no injuries. The avalanche was anywhere from 10-40 cm deep, 10 m wide and 10 m long. With warming and periods of intense solar radiation avalanche danger, weak cornices will likely fail and loose wet avalanches will 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 a variety of old persistent weak layers including crusts, facets and spotty surface hoar on northerly aspects which were buried April 10th. 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.

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.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of a buried crust/facet layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

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.

Give cornices a wide berth when travelling on or below ridges.>Pay attention to overhead hazards like cornices.>

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 sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Valid until: Apr 17th, 2015 2:00PM