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Avalanche Forecast

Apr 11th, 2012–Apr 12th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Cariboos.

Confidence

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

Weather Forecast

Thursday: Moderate precipitation continuing overnight / moderate westerly winds / freezing level at 1600m Friday: Light precipitation with locally moderate accumulations continuing overnight / moderate westerly winds / freezing level at 1700m Saturday: generally clear skies / light and variable winds / freezing level at 1900m

Avalanche Summary

On Sunday, a very large (size 3) naturally-triggered avalanche was reported on an east aspect at 2700 m that initiated on the late March crust and then stepped down to glacier ice. More recently, there have been numerous loose snow avalanches running on steep solar aspects to size 2.5. With forecast weather, I expect a shift from wet snow avalanches to storm snow instabilities at higher elevations, while wet snow instabilities will still exist below treeline.

Snowpack Summary

Melt-freeze conditions exist to about 2100m on all aspects and to ridge top on solar aspects. On shaded aspects higher up, 60 cm of recent storm snow is reported to be generally settling well with recent warm temperatures and generally light winds. However, shears may still exist within the storm snow. Additionally, a crust that formed near the end of March is a concern, particularly on steep, solar aspects. With prolonged warming, there is the possibility for wet slabs to release on this layer, or potentially on deeper layers (including the ground), as melt water starts to percolate through the snowpack. Cornices are large in some areas and drooping with recent warm temperatures.

Avalanche Problems

Wind Slabs

Forecast wind and new snow will create fresh windslabs on lee terrain at higher elevations.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Loose Wet

Forecast rain at lower elevations has the potential to promote ongoing loose wet avalanche activity. Rain can also trigger destructive glide cracks where they exist.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Cornices

Large cornices exist in alpine terrain. A failure could be destructive by itself, and could also trigger an avalanche on the slope below.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 5