Avalanche Forecast

Issued: Mar 14th, 2015 9:43AM

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

rbuhler, Avalanche Canada

South Columbia.

Stormy conditions continue on Sunday in the south of the region. Tricky conditions are expected in the alpine and conservative decision making is essential.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Variable conditions are expected for Sunday across the region. A storm system will track south of the US border on Sunday but should bring light to moderate precipitation to the southern end of the region. A ridge of high pressure building over central BC may keep the north of the region mainly dry. There is quite a bit of uncertainty regarding the northern extent of the storm. Freezing levels on Sunday are expected be around 1500m and alpine winds should be moderate from variable directions. On Monday, there is once again uncertainty regarding locations with precipitation but it looks like the north of the region should stay mainly dry while the south of the region gets light precipitation. Winds should be light and freezing levels around 1500m. Tuesday looks to be unsettled and freezing levels may reach over 2000m.

Avalanche Summary

On Friday, reported activity was limited to loose wet avalanches from steep sun-exposed slopes. On Tuesday through Thursday, several natural avalanches were reported to have released on the ground. These were on solar aspects and the largest were size 3. Natural and skier triggered wet sluffing was also reported up to size 2. On Thursday, several small wind slabs were triggered by skiers. On Sunday, touchy wind slabs are expected in the alpine and loose wet sluffing is possible from steep slopes at lower elevations. There is a still a concern for avalanches to step down to deeply buried weak layers resulting in larger persistent slab avalanches.

Snowpack Summary

At higher elevations, new snow sits over a variety of surfaces including moist snow, crusts, wind affected surfaces, and/or old wind slabs which may still be reactive. Rain has soaked the upper snowpack to around treeline elevation. In the alpine, strong winds during the storm are redistributing the new snow into wind slabs in leeward terrain features. Prior to the storm, 10-30cm of snow was sitting over a weak facet/crust layer that was buried in mid-February. The late-Jan crust/surface hoar layer (around 1m deep) and the mid-January surface hoar (around 1.5m deep) have been dormant for several weeks but now have the potential to wake-up with the current warm temperatures and new loading. A basal weakness has recently become active with the warm conditions and several avalanches have released to the ground.

Problems

Wind Slabs

At higher elevations, new snow and strong winds have formed wind slabs. Warm temperatures and an underlying weak layer may increase the likelihood of triggering these wind slabs.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 3

Loose Wet

Ongoing rain at lower elevations may result in loose wet avalanches releasing from steep terrain.

Avoid avalanche terrain during periods of rain.>Sluffs may trigger deeper instabilities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

New loading from rain or snow coupled with the persistent warm conditions may overload buried persistent weak layers resulting in very large avalanches.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Mar 15th, 2015 2:00PM