Avalanche Forecast

Issued: Mar 17th, 2013 10:28AM

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

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Synopsis: Northwest flow gives way to a frontal system that impacts the region on Tuesday afternoon and into Wednesday.Monday: Patchy convective snowfall. Some areas may see nothing, others 2-5 cm. Some sunny breaks in the cloud giving daytime warming. Afternoon freezing level around 800 m. Winds gusty from the northwest.Tuesday: Day starting clear, but clouding over then moderate snowfall starting in the afternoon. 10-20 cm overnight. Freezing level around 1200 m. Southwest winds increasing to 60 km/h at ridgetop.Wednesday: Around 20 cm new snow. Freezing level around 1200 m. Southwest winds around 25 km/h.

Avalanche Summary

On Saturday, a size 1.5 natural avalanche was reported from a north aspect at 1900 m, with a crown of 50 cm failing on the surface hoar/crust layer from March 11th. Soft slab avalanches to size 1.5 could also be triggered on this layer from steep rolls at treeline and below treeline. On Friday, loose natural avalanches up to size 2.5 were reported from treeline and below treeline due to warm daytime temperatures. Two skier-triggered avalanches and one vehicle remote triggered avalanche were also reported from north aspect slopes between 1800 and 2000 m.

Snowpack Summary

10-20 cm new snow now sits on a weak crust below 1900 m. Below the crust is moist snow, from the previous intense, wet storm. Freeze-up following this storm was slow, due to a slow decline in temperatures and the insulating skiff of snow on the surface. Below the recent new snow lies one or two weak layers buried approximately 60 cm below the surface. These comprise faceted snow, surface hoar and/or a crust. The snowpack structure is quite variable at this time. It may change dramatically with only a subtle change in elevation, aspect, wind or sun exposure. With further cooling, the upper snowpack should start to bond better. However, with the amount of moisture and the insulating effect of the new snow, expect this to take longer than usual. Mid and lower snowpack layers are well bonded.

Problems

Storm Slabs

An icon showing Storm Slabs
There's a lot of uncertainty surrounding the new/old snow interface, buried 50-80 cm below the surface, which consists of surface hoar, old wind slabs and crust. This interface still has the potential to produce dangerous avalanches.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be alert to conditions that change with elevation.>Avoid large alpine features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Cornices

An icon showing Cornices
Cornices are reported to be very large at this time. They are a danger in themselves, but could also trigger a slab avalanche on the slope below.
Do not travel on slopes that are exposed to cornices overhead.>Give cornices a wide berth when travelling on ridges.>

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 18th, 2013 2:00PM

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