Avalanche Forecast

Issued: Apr 13th, 2015 9:17AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

swerner, Avalanche Canada

Sea To Sky.

Tricky winter conditions exist at higher elevations. Spring-like, convective weather directly influences the snowpack and avalanche hazard can change quickly. Use a conservative approach and watch for signs of instabilities.

Summary

Confidence

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

Weather Forecast

Winter continues on the coast as an upper trough moves across the province. A cool and unstable air mass will bring spring-like convective conditions including sunshine, moderate westerly ridgetop winds and localized snow squalls. Tuesday will mostly be a mix of sun and cloud with freezing levels near 1400 m and precipitation 2-7 mm. Wednesday will remain mostly cloudy with moderate to strong westerly ridgetop winds. Thursday, the winds will howl strong from the west at ridgetop and precipitation amounts up to 10 mm. Freezing levels will hover around 1500 m on Thursday and the rise throughout the day to 2500 m Friday night.

Avalanche Summary

Reports of a human triggered size 2 storm slab was remotely triggered 15 m away. There was no personal involvement, however the slab did fail on facets above a crust which was buried on April 10th. Explosive control work triggered several size 1.5 loose dry avalanches and no new naturals were reported.

Snowpack Summary

Up to 25 cm of recent storm snow sits on a variety of old snow surfaces including crusts, facets and spotty surface hoar which was buried on April 10th. This interface has shown a poor bond and has been reactive to human triggers remotely. Moderate to strong south west winds has redistributed the recent storm snow into wind slabs on leeward slopes and terrain features. Â The mid-March persistent weak interface has been producing hard but sudden planar results in snowpack tests. This remains a concern in the region due to its potential to produce very large avalanches. There may be 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

Wind Slabs

Strong winds have built wind slabs in lee terrain in the alpine and at treeline. They are especially touchy where they sit on buried facets, surface hoar and/ or crusts. Give looming cornices a wide berth if the sun comes out.

Avoid freshly wind loaded features.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Pay attention to overhead hazards like cornices, especially when the sun is shining.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

No recent activity has been reported on this layer, but it's still there, and could produce a large avalanche if triggered. Large loads like cornice fall, or hitting the sweet spot in thin-thick snowpack areas could act as a trigger.

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

Unlikely - Possible

Expected Size

2 - 5

Valid until: Apr 14th, 2015 2:00PM