Avalanche Forecast

Issued: Mar 26th, 2015 9:32AM

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

ccampbell, Avalanche Canada

Sea To Sky.

Unusual persistent slabs continue to produce very large human triggered avalanches. See the latest forecaster blog for a more in depth look at this situation: http://bit.ly/1HHQrK2

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Warm weather is expected to continue for Friday with freezing levels as high as 2600 m and possible light rain showers, before another storm arrives in the afternoon. Expect 5-10 cm of fresh snow by Saturday morning falling under moderate southwesterly winds with freezing levels back down to 1700 m. Continued light snow flurries are expected Saturday morning before an organized system brings another 5-15 cm overnight and 10-15 cm throughout the day on Sunday. Freezing levels hovering around 1700 m and moderate to strong southwesterly winds expected during the height of the storm on Sunday.

Avalanche Summary

Over the past week, very large slab avalanches have been running on the mid-March persistent weak layer. What makes this spooky is that the majority of these avalanches have been remote triggered, some from as far as 200m away. This interface remains very reactive. While it's a few days old now, the photo in this Mountain Information Network post provides a very powerful visual: http://bit.ly/1CS2Nld

Snowpack Summary

Warm temperatures and light rain have promoted settlement within the most recent recent storm snow, but the region has a very serious persistent slab problem just under the surface. A 50 to 150cm thick slab is poorly bonded to the facet/crust persistent weak layer buried mid-March. This interface has been incredibly volatile recently and remains sensitive to human triggering. Recent compression tests have produced sudden planar failures at this interface. At lower elevations, rain has saturated the snowpack. The mid and lower snowpack are generally well-settled and strong.

Problems

Persistent Slabs

High variability and severe consequences makes the mid-March persistent weakness very untrustworthy. Riders continue to remote trigger very large avalanches, even when riding in conservative terrain.

Avoid steep high consequence terrain, convexities and areas with a thin and/or variable snowpack.>Remote triggering is a concern, watch out for adjacent slopes.>Stick to simple terrain and be aware of what is above you at all times. Cornice fall will become more likely in the afternoon.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 5

Valid until: Mar 27th, 2015 2:00PM