Avalanche Forecast

Issued: Apr 1st, 2018 4:38PM

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

Avalanche Canada cgarritty, Avalanche Canada

Avalanche activity over the course of the storm has been extensive. Maintain conservative terrain selection while human-triggering remains a concern. Isolated areas will see storm slabs continue to build over Sunday night.

Summary

Confidence

Moderate -

Weather Forecast

Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light variable winds. Alpine high temperatures around -10.Tuesday: Mainly cloudy with isolated flurries and a trace to 3 cm of new snow. Light southwest winds. Alpine high temperatures around -9Wednesday: Mainly cloudy with isolated flurries and a trace of new snow, increasing overnight. Light southeast winds. Alpine high temperatures around -6.

Avalanche Summary

Reports from Saturday included numerous observations of storm slabs releasing naturally as well as with remote (from a distance) triggering, skier traffic and explosives control. Sizes ranged from 2-3, with crown fracture depths varying from 30-100 cm. This activity occurred on all aspects but was focused at alpine elevations.Friday's storm caused a natural avalanche cycle with numerous size 1-2 avalanches in the top 20-30 cm of new snow. Storm slabs were also reactive to skiers, producing several size 1 avalanches on small terrain features on various aspects.Storm slab avalanches have been reported on a regular basis since Tuesday's storm. Natural avalanches up to size 3 were reported from Tuesday's storm on all aspects from 1900-2800 m. South and west aspects were the most reactive with slabs running on the recently buried late-March crust. In the days following the storm, several size 2 skier and remotely (from a distance) triggered storm slab avalanches were reported. Activity on Thursday was mostly on east aspects at treeline. Skier triggered slabs were mostly 30-50 cm thick and ran on the late-March layer.

Snowpack Summary

Another 20-30 cm of new snow on Friday brought the weekly total throughout the region to 40-80 cm. Strong west winds have redistributed the snow in alpine and treeline terrain.The storm snow sits on a layer buried in late-March that consist of crusts below 1900 m and on south aspects, and surface hoar on shaded aspects at higher elevations.A deeper layer buried mid-March is now 60 to 90 cm below the surface, and is similar to the late-March interface.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.

Problems

Storm Slabs

An icon showing Storm Slabs
Human-triggered storm slabs remain a concern on wind-affected features and on south aspects where they sit above buried sun crusts. Periods of sunshine may also undermine stability on any sun-exposed slopes.
Minimize exposure to steep planar south-facing slopes - especially if they see sunshine.Choose well supported terrain without convexities.Be careful with wind loaded and cross-loaded slopes, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1.5 - 3

Valid until: Apr 2nd, 2018 2:00PM

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