Avalanche Forecast

Issued: Apr 16th, 2015 9:36AM

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

swerner, Avalanche Canada

South Coast.

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 - Due to the number of field observations

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 2000 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, natural cornice fall was reported, pulling thin slabs up to size 1 from the slopes below. Strong solar radiation and warming expected through the forecast period. This will likely initiate a natural avalanche cycle. Watch overhead hazards like cornice failures and solar induces loose wet, and slab avalanches.

Snowpack Summary

Anywhere from 20 to 50 cm of recent storm snow sits on a persistent weak layer comprising of crusts, surface hoar and facets which were buried April 10th. Moderate to strong south west winds are redistributing the storm snow into wind slabs on leeward slopes and terrain features. The mid-March persistent weak layer of facets on a crust is now approximately 50-100 cm down and continues to sit 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 20-50 cm and has been recently reactive naturally and to human triggers. The second one sits 50-150 cm down and may re-awaken with warming, cornice fall and step down avalanches.

Smaller surface avalanches and cornice fall could act as a trigger, initiating avalanches on the deeper buried weak layer.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Loose Wet

Solar radiation and rising freezing levels will deteriorate the snowpack. Travel on sunny slopes early, and watch for obvious 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.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

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.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

3 - 5

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