Avalanche Forecast

Issued: Mar 25th, 2015 10:18AM

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

ghelgeson, Avalanche Canada

Sea To Sky.

Warming temperatures are expected to increase the reactivity of the persistent slab which continues 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

Poor

Weather Forecast

Thursday: Light rain. Freezing level starting around 2300m, rising to approximately 2600m by sundown. Light SW winds at treeline, strong SW winds at ridgetop.Friday: Light rain. Freezing level starting around 2500m, lowering to around 1800m by dinner time. Moderate SW winds at treeline, strong SW winds at ridgetop.Saturday: Light rain. Freezing level starting around 1200m rising to 1500m during the day. Few clouds initially, cloud cover increasing throughout the day. Light SW winds at treeline, moderate SW winds at ridgetop.

Avalanche Summary

Over the past week, very large slab avalanches have been running to size 3, failing 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

5 to 10 cm of new snow has fallen over the last 48 hours. This recent dusting has made for great riding, but the region has a very serious persistent slab problem just under the surface. Old storm snow from the last week is settling into a cohesive slab 40 to 120cm in depth that rests on the mid-March persistent weak layer that consists of small grain facets on a crust. 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

It's difficult to say which pieces of terrain are capable of producing very large avalanches and which are not. Riders continue to remote trigger very large avalanches, even when riding in conservative terrain.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 5

Valid until: Mar 26th, 2015 2:00PM