Avalanche Forecast

Issued: Apr 7th, 2012 4:00PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Loose Wet, Persistent Slabs and Cornices.

pmarshall, Avalanche Canada

South Coast.

Avalanche danger will rise during the day with intense spring sunshine and warming temperatures. Plan to be off big sun-exposed slopes early before the snow becomes moist or wet.

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

Sunday: Sunny during the day with increasing cloud in the afternoon/evening. Winds are light from the south-southeast. The freezing level should be around 1800-2000. Monday: Mainly cloudy with some sunny breaks and a chance of light precipitation. Winds are light to moderate from the southeast. The freezing level hovers around 1800-2000m.Tuesday: Mainly cloudy with light precipitation ~ 5mm. The freezing level stays fairly high at 2000-2200m.

Avalanche Summary

A Size 2 skier-triggered avalanche was reported in the Duffey Lake area on Friday. It was triggered on a NE facing alpine slope and is suspected to have failed on the late March sun crust. There have also been a reports of isolated natural slab avalanches to Size 2.5, primarily on solar aspects during the afternoon. Loose wet activity continues on steep solar aspects.

Snowpack Summary

The snow surface consists of old wind slabs in exposed alpine terrain, spotty surface hoar on shady slopes, and a sun crust/moist snow on solar aspects. This sits on up to a metre of settling storm snow from last week. The March 27 layer, predominately crusty interface except north facing slopes at treeline and above where small surface hoar (5mm) may be found, is now down 60-120cm. Recent reports include hard but sudden compression tests results and a Rutschblock 4 whole block failure on this late-March surface hoar in the Duffey Lake area. Deep persistent weaknesses linger in many colder and shallower snowpack areas. Not only will daytime warming and sun-exposure cause surface snow to lose cohesion and cornices to weaken, they will also increase settlement rates and decrease slab stability.

Problems

Loose Wet

Loose-wet avalanches are very likely in steeper south facing terrain during the afternoon. A heavy wet slide could have serious consequences if you are exposed to a terrain trap.

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

Elevations: Alpine, Treeline.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

Becoming lee likely, but there is potential for remote triggering, step down avalanches, and wide propagations on the late March interface down 50-120cm. .

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Cornices

Large and weak cornices could easily start popping off with sun-exposure. Not only are they a hazard in themselves, but can also act as a heavy trigger for very large avalanches on the slope below.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Apr 8th, 2012 9:00AM