Avalanche Forecast

Issued: Mar 29th, 2015 8:49AM

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

jfloyer, Avalanche Canada

South Coast.

Variable precipitation amounts expected. If your riding area sees more than 20 cm new snow or 20 mm rain, consider the avalanche danger to be high. See this blog post for more info about the tricky persistent slab problem: http://bit.ly/1HHQrK2

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Only relatively light amounts of precipitation are expected to spill into the inland region from storms impacting the coast through this period. Monday: 1-3 mm expected in most areas during the day, maybe 5 mm on the Coquihalla, then an additional 5-10 mm overnight from 4pm Monday to 4am Tuesday. Freezing level around 1900 m, ridgetop winds around 60 km/h from the SW. Tuesday: Unstable air bringing convective showers is expected to bring highly variable precipitation. Seeing 10 mm from an intense shower is possible, as is getting no precip at all. Freezing levels are expected to drop to around 1200 m and winds are expected to diminish to around 35 km/h from the west. Wednesday: Mostly dry with the occasional light shower. Freezing levels around 1400 m, winds light northwesterly.

Avalanche Summary

On Saturday, two size 2 wind slab avalanches were reported from the north of the region. For a little over a week, there have been consistent reports of avalanches to size 2.5 occurring on the mid-March persistent weak layer. Some avalanches have occurred naturally and many have been remote triggered from up to 100m away.

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 40-120 cm below the surface. Avalanches have continued to run on this layer at upper treeline and alpine elevations, especially in the north of the region. Snowpack layers deeper than this critical interface are reported to be generally well-settled and strong.

Problems

Persistent Slabs

There is a possibility that a touchy persistent weak layer buried an average of 80 cm below the surface could become overloaded by new rain and snow. Since this layer is now quite deep, this could result in some large and destructive avalanches.

Remote triggering is a concern, watch out for adjacent slopes.>Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Wind Slabs

Forecast new snow (above around 1800 m) and strong winds are likely setting up wind slabs in exposed lee terrain at higher elevations.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Minimize exposure during periods of heavy loading from new snow, wind.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Valid until: Mar 30th, 2015 2:00PM