Avalanche Forecast

Issued: Feb 21st, 2014 9:03AM

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

swerner, Avalanche Canada

South Rockies.

The snowpack is touchy and primed for human-triggered avalanches. Don't let the improving weather lure you into high risk scenarios.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

High pressure building off the coast and pushing north will be responsible for a cooler and dryer NW flow. Some unstable disturbances are embedded in this flow, bringing scattered cloud and light precipitation. Models disagree with timing and precipitation amounts.Saturday: Mix of sun and cloud. Light snow possible. Alpine temperatures near -12.0. Light NW ridgetop winds.Sunday: Cloudy with sunny periods and trace snow amounts. Alpine temperatures near -21.0. Ridgetop winds moderate from the North.Monday: Sunny. Alpine temperatures near -22.0. Ridgetop winds blowing light from the north.

Avalanche Summary

On Friday, the SR field team witnessed several large snowmobile remote triggered slab avalanches in the Elk Valley North. These avalanches were all triggered below treeline around 1800 m. On Thursday, a natural size 2.5 avalanche occurred near the Coal Creek road. The debris just reached the road, didn't block it but the air blast covered the road with branches. On Wednesday, there was a size 4.0 natural slab avalanche in the neighbouring Lizard range that ran full path and piled up debris including mature timber in the valley bottom. Wind loading and sunshine are expected, natural avalanche activity may pick up; however, conditions are primed for human triggered slab avalanches.

Snowpack Summary

Up to 15 cm of new snow fell on Friday, adding to the recent storm snow that is close to a metre thick. This slab continues to settle and become more cohesive, overlying a complex medley of persistent weak layers (mainly facets and some surface hoar). This weak layer is below the storm slab and widespread on all aspects and at all elevations across the region. This is the classic firm slab over soft and weak layer that allows for wide propagations and remote triggering. This problem may persist for days after the storm or even weeks. Wind loading and sunshine may cause another natural avalanche cycle on this layer. The mid snowpack is strong and supportive. A deep persistent layer of facets and depth hoar near the base of the snowpack has remained dormant to this point, but may become a concern with additional load and stress on the snowpack.

Problems

Persistent Slabs

The early February weak layer continues to be very sensitive to any additional load. Remote triggering from adjacent terrain and very long fracture propagations are a concern. If triggered large to very large avalanches are expected.

Use conservative route selection, resist venturing out into complex terrain even if you observe no obvious signs of unstable snow.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar and facetted snow.>Avoid lingering in runout zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

3 - 6

Storm Slabs

The storm slab may release naturally in the alpine where wind transport may continue to add a new load. The storm slab is expected to continue to be very sensitive to human triggers at all elevations.

Extra caution needed around cornices with current conditions.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Feb 22nd, 2014 2:00PM