Avalanche Forecast

Issued: Mar 10th, 2014 10:05AM

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

jlammers, Avalanche Canada

South Columbia.

The big storm may have passed, but elevated danger ratings will persist, especially with forecast warm temperatures. If the sun comes out, the avalanche danger may become HIGH.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

We can expect a mix of sun and cloud for the forecast period as a ridge of high pressure pushes into the province. Ridgetop winds should remain light to moderate from the west-northwest. Freezing levels should sit at about 1500m on Tuesday, rising to about 1800m on Wednesday and then dropping back to about 1500m on Thursday.

Avalanche Summary

On Saturday an avalanche resulted in a fatality in the southwest corner of the region. More details will follow as they become available. On Sunday a widespread natural avalanche cycle to size 3.5 took place. The avalanche activity occurred in response to strong wind, snow and warming over the weekend. Much of the activity occurred within the storm snow, while many avalanches stepped down to the February 10th interface. On Monday, explosives control triggered a few persistent slab avalanches to size 3.5. On the same day, a group of slackcountry skiers triggered a size 2.5 slab avalanche. Nobody was injured in the event.Looking forward, another natural cycle may occur on solar aspects with forecast sunny breaks and warming.

Snowpack Summary

In some areas over 80cm of recent storm snow overlies small surface hoar in sheltered areas and a sun crust on previously sun exposed slopes. In wind exposed terrain these new accumulations have been pushed into much deeper deposits by generally moderate southwest winds. Wind and warming have also created an "upside down" storm slab which may be particularly touchy where it overlies the buried crust. Many slopes below 1850m saw rain over the weekend and the snowpack at lower elevations is now mostly saturated. At ridgetop cornices are large, unsupported and waiting for the right trigger.We're still seeing avalanches on a mix of weak surfaces which were buried on February 10th. This persistent interface lies between 100 and 200cm below the surface, and includes surface hoar, well developed facets and a mix of hard surfaces which remain widespread at all aspects and elevations. This deeply buried layer still has the potential to "wake up" and create very large and destructive avalanches. Possible triggers include a surface avalanche in motion or a cornice fall.For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

Storm Slabs

Solar warming may reactivate natural activity within the recent storm slab which may be particularly reactive where it overlies a buried crust. Recent storms have also formed very large and unstable cornices.

Be alert to conditions that change with elevation.>Be cautious as you transition into wind affected terrain.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

The early February weak layer may be stubborn to initiate, but could still be triggered by a large force such as a storm slab in motion or a cornice fall. Warming and solar radiation over the next few days may also activate this destructive layer.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 7

Loose Wet

Elevated freezing levels and the possibility of sun over the next few days will increase the chances of loose wet avalanches. A loose wet avalanche in motion may trigger deeper instabilities.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious of wet sluffing in steep terrain.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Mar 11th, 2014 2:00PM