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Avalanche Forecast

Mar 4th, 2012–Mar 5th, 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
4: High
The avalanche danger rating in the alpine will be high
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: South Columbia.

Confidence

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

Weather Forecast

Monday: A cold front brings moderate to heavy snow overnight Sunday. This is forecast to continue on Monday until the front departs in the afternoon. Moderate to strong south-westerly winds, switching to north-westerly and decreasing. Freezing level around 1200m, falling to around 900m.Tuesday: A brief ridge of high pressure should bring a break in precipitation and possibly clear skies and sunshine, although northern areas may cloud over by afternoon. Light winds. Cool temperatures, except in areas with direct solar warming.Wednesday: North-westerly winds increasing. Cloudy. Freezing level rising to around 1300m.

Avalanche Summary

A natural avalanche cycle began on Saturday in response to snow, wind and warming. Some operators reported numerous size 1-3 natural avalanches, starting in the alpine on all aspects. Skier-triggered slabs were also reported in the size 1-2 range, failing on storm snow weaknesses. Previously this week, many avalanches were triggered remotely (from several hundred metres away) and accidentally by skiers and machinery. These avalanches failed on upper snowpack persistent and storm snow weaknesses, on a variety of aspects and elevations.

Snowpack Summary

Snow is falling with strong winds and fluctuating temperatures, creating a perfect recipe for storm slab and wind slab instabilities. This new snow is landing on variable surfaces including surface hoar and facets. Widespread persistent weak layers buried in February have remained touchy all week and are a key concern at all elevations. Storm slabs, wind slabs and sluffs (or you) could trigger these deeper weaknesses, creating avalanches which are larger than you expect, given the amount of fresh snow. Large cornices also loom as potential triggers for deep avalanches.

Avalanche Problems

Storm Slabs

Snow is falling with fluctuating temperatures, causing storm slab development. Storm slabs could step down to a persistent weak layer, creating surprisingly large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 7

Wind Slabs

Strong winds are creating widespread wind slabs, even at treeline. Large cornices also threaten many slopes.

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 6

Persistent Slabs

Touchy persistent weak layers, found at all elevations, are tricky to manage. These may be triggered naturally during the storm, or by a light additional load, like a sled or skier, even on low-angled slopes or from a distance.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 7