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Avalanche Forecast

Mar 15th, 2012–Mar 16th, 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
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
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
4: High
The avalanche danger rating at treeline will be high
Below Treeline
4: High
The avalanche danger rating below treeline will be high

Regions: Cariboos.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Friday: Chance of broken cloud in the morning with light snow in the afternoon - light to moderate southwest winds - freezing level at 900m Saturday: very light snowfall with a chance of intermittent sun until mid afternoon - light and variable winds increasing in the evening freezing level at 900m Sunday: scattered cloud - light southwest winds - freezing level at 900m Note: Solar radiation will have an increasing presence throughout the region over the forecast period. My best guess is that on Friday and Saturday morning there will be short lived localized bursts of sun with a more general clearing pattern expected for Sunday.

Avalanche Summary

Recent avalanche observations have been fairly limited due to inclement weather. Having said that, evidence of a widespread natural cycle to size 3.5 was observed on Wednesday. I expect ongoing natural avalanche activity throughout the forecast period, especially with forecast increasing solar radiation.

Snowpack Summary

Recent snowfall amounts have been quite variable throughout the region. Generally speaking, ongoing moderate daily amounts and moderate to strong southwest winds have contributed to reactive wind and storm slab development. This recent snowfall has added to a deep and cohesive slab that overlies weak surfaces that formed early February. This interface, which lies between 1 and 2 metres below the surface, includes a widespread surface hoar instability that, depending on aspect an elevation, may exist in combination with facets or crusts. These persistent weak layers have been reactive all week and remain a concern at all elevations. The weight of new snow, near-surface avalanches, sleds, and skiers may easily trigger these deeper weaknesses creating unexpectedly large and destructive avalanches.Large cornices have also formed and could act as triggers for slopes below.

Avalanche Problems

Persistent Slabs

Persistent weaknesses are buried upwards of 150cm below the surface. Surprisingly large and destructive avalanches could be triggered naturally by the weight of additional snowfall, or by the energy of a person/sled.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 3 - 7

Wind Slabs

Forecast snow and strong winds will continued to form reactive wind slabs on lee features. Large cornices may also act as a trigger on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood: Very Likely

Expected Size: 1 - 5

Storm Slabs

With ongoing snowfall, storm slabs will form on all aspects and elevations. Surprisingly large, destructive avalanches will occur if storm slabs step-down to a persistent weak layer buried below.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5