Avalanche Forecast

Issued: Apr 15th, 2015 9:14AM

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

swerner, Avalanche Canada

Sea To Sky.

Tricky winter conditions exist at higher elevations. Solar radiation and rising temperatures are forecast and avalanche hazard can rise quickly. Use a conservative approach and watch for signs of instabilities.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

The current wintery weather pattern begins to change as an upper ridge sets up over the province. The next frontal system seems to just skirt the South Coast region bringing little to no precipitation. Thursday and Friday will see a mix of sun and cloud with light precipitation. Ridgetop winds will be light from the west, gusting moderate. Freezing levels will rise to 2400 m. Saturday will be mostly sunny with alpine temperatures rising to +6.0 degrees and light ridgetop winds. Freezing levels will remain at 2500 m. The ridge dominates through the weekend and will remain stationary until Wednesday bringing warm air and sunny skies.

Avalanche Summary

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. Natural loose wet avalanches occurred up to size 1.5 from steep solar aspects and an explosive triggered size 2 cornice failed, which entrained the recent storm snow but did not pull a slab. With warming and periods of intense solar radiation, persistent slabs may re-awaken, 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 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 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 persistent weak layer is down 100-150 cm and has been producing hard but sudden planar results in snowpack tests. This remains a concern in the region. 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 redistributed recent storm snow into wind slabs on leeward slopes and behind terrain features. They are 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.>Pay attention to overhead hazards like cornices, especially when the sun is shining.>

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

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, it could produce a large avalanche if triggered. Large loads like cornice fall, intense warming, 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

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 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

Likely - Very Likely

Expected Size

1 - 3

Valid until: Apr 16th, 2015 2:00PM