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Avalanche Forecast

Feb 20th, 2012–Feb 21st, 2012
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Sea To Sky.

Confidence

Fair - Intensity of incoming weather is uncertain

Weather Forecast

The arrival of the next frontal system should come Monday night into Tuesday bringing light-moderate snowfall amounts which will intensify later Tuesday. Tuesday: New snow 15-25cm. Ridgetop winds 70-80km/hr from the West. Treeline temperatures near -2, with freezing levels up to 1200m. Wedneday: Snow amounts 5-10cms. Ridgetop winds from the NW 55-75km/hr. Freezing levels falling to valley bottom. Thursday: Trace amounts. Moderate NW ridgetop winds.

Avalanche Summary

Most recent avalanche activity has been a size 2 natural that occurred on a NW aspect @ 1900m. The depth was 50-55cm, 70m wide and running on a buried facet layer. There was also a size 2 skier triggered avalanche in the Blackcomb backcountry (outside the ski area boundary). This was on a North aspect @ 2300m. No burials or injuries reported. Several small size 1-1.5 skier triggered slides have also been reported. I suspect there will be an increase in avalanche activity with the forecast wind and snow. It may be a good time to wait out the storms until the new snow has a chance to settle out and bond.

Snowpack Summary

Heavy snowfall and strong winds on Friday night created new wind and storm slabs and continued to cover an assortment of old snow surfaces. These old surfaces are now 30-45cm down and include crusts that exist on all aspects at lower elevations and on steep solar aspects higher up. Facets (sugary snow crystals) and spotty surface hoar (feathery snow crystals) may also exist in combination with crusts, so there may be continued slab reactivity at lower elevations. With more snow and wind in the forecast the new load may have a poor bond to the underlying buried surfaces. The mid and lower snowpack are strong and well settled. The average treeline snowpack depth is about 240cm.

Avalanche Problems

Wind Slabs

Strong winds and heavy snowfall will likely create new wind slabs in the alpine, and exposed locations at treeline.

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Storm Slabs

Storm slabs will continue to grow with forecast snow. They may be particulary reactive where they exist in combination with buried crusts.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5