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Archived

Avalanche Forecast

Feb 28th, 2013–Mar 1st, 2013
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
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
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 Coast.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

Thursday night: Moderate precipitation. Strong to extreme S winds. Freezing level around 1500-1800 m.Friday: Steady, moderate to heavy precipitation. Strong to extreme SW winds. Freezing level around 1800 m.Saturday: Light to moderate precipitation. Winds easing to moderate southerly. Freezing level around1800 m, lowering to  around 1000 m.Sunday: Lingering snow showers could bring up to 15 cm snow. It may clear up. Light winds. Freezing level around 800 m.

Avalanche Summary

Almost every day this week, skiers have triggered slabs to size 2, failing on buried surface hoar/crusts which exist at all elevations and on all aspects. Some were triggered remotely, and they exhibited wide propagation. Details of some of these incidents can be found here. A natural cycle to size 2.5 occurred on Sunday night and Monday in response to new snow and wind-loading. A natural avalanche cycle is expected over the next few days in response to intense storm loading.

Snowpack Summary

Two very touchy weaknesses of surface hoar and/or a crust within the upper metre or so of the snowpack have already been responsible for a number of avalanche incidents. Add an intense storm, with heavy precipitation rates, warming and very strong winds, and we have a good recipe for widespread avalanche activity. The lower snowpack is well settled.

Avalanche Problems

Storm Slabs

Storm snow is expected to become very touchy with continuous loading throughout the forecast period, especially where wind-loaded. Storm slabs may step down to persistent weaknesses, creating very large avalanches.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 1 - 4

Persistent Slabs

Persistent weaknesses buried last week are extremely touchy, can be triggered from a distance, and may create surprisingly large avalanches.
Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>Remote triggering and propagation across low-angled terrain is a concern.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 3 - 7