Avalanche Forecast

Issued: Mar 28th, 2015 3:00PM

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

Avalanche Canada jfloyer, Avalanche Canada

Don't underestimate the avalanche danger at this time. Forecast new snow and rain could overload a significant weak layer with the potential to release very large avalanches. See this blog post for additional info: http://bit.ly/1HHQrK2

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

A series of wet storms are set to impact the coast until Tuesday morning then a cooling trend. Saturday night: 15-25 mm precip can be expected between 4pm Saturday and 4am Sunday with freezing levels around 1700 m and strong southwesterly winds. Sunday: A further 15-25 mm precip is expected with freezing levels around 1900 m and southwest ridgetop winds gusting to 60 km/h. Monday: Another pulse looks to bring 10-20 mm precip with freezing levels around 1900 m and southwest ridgetop winds gusting to 60 km/h. Tuesday: Possibility of lingering storms that could bring highly variable precipitation. A cooling trend is expected to lower freezing levels to around 1000 m. Winds are expected to diminish.

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

This region has a very serious persistent slab problem that exists under the upper layers of dense storm snow. Depending on how much recent snow has fallen, a facet/crust persistent weak layer buried mid-March lies anywhere from 50-150 cm below the surface. This interface has been incredibly volatile recently and remains sensitive to human triggering, especially where the slab is thinner. Recent compression tests have produced sudden planar failures at this interface. At lower elevations, rain has saturated the snowpack. Layers below the critical mid-March interface are generally considered to be well-settled and strong.

Problems

Persistent Slabs

An icon showing Persistent Slabs
There is significant danger that the touchy persistent slab buried an average of a metre below the surface will become overloaded by new rain and snow. The depth of this layer could result in some particularly large and destructive avalanches.
Remote triggering is a concern, watch out for adjacent slopes.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

3 - 7

Storm Slabs

An icon showing Storm Slabs
An active weather pattern is expected to develop new storm slabs on all aspects above around 1800 m. These will be especially touchy where they are drifted into fat pillows by the wind.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 4

Valid until: Mar 29th, 2015 2:00PM