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Archived

Avalanche Forecast

Dec 4th, 2012–Dec 5th, 2012
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
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
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

Regions: Kananaskis.

Another day with HIGH danger ratings for the alpine due to extensive redistribution of storm snow and rapid slab formation, primarily on north and east aspects. Pockets of increased danger may exist at treeline as well.

Confidence

Good

Weather Forecast

Strong to extreme W-SW winds are expected to persist for another day and with so much loose dry snow available for wind transport we are seeing rapid loading onto lee aspects and the storm slabs are stiffening and becoming more reactive to loading.  Temperatures over the next 24+ hours will drop into the -20 degree range at 3000m elevation.

Avalanche Summary

One skier controlled Size 2 on NE as at TL.  50-70cm deep x  75m wide.  Ran full path (a 30m high convex roll).  Storm slab was F-4F resistance overlying a 1F old snow surface.  Limited observations due to obscured sky conditions.

Snowpack Summary

Extensive redistribution of storm snow at TL/ALP with cornice growth enhanced.  Test profile at TL produced minor CTM12-15 (SP) in top 20cm of settled HST.  CTH 26 (SP) down 88cm on 121106 RC.

Avalanche Problems

Storm Slabs

Additional 10+cm of new snow overnight with storm snow totals near 60cm. Storm slab formation is rapid in the Alpine and isolated areas at Treeline due to strong to extreme W winds. The storm slabs are becoming increasingly more cohesive and touchy.
Assess start zones carefully and use safe travel techniques.>Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid convexities or areas with a thin or variable snowpack.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely - Very Likely

Expected Size: 1 - 5

Loose Dry

Loose dry avalanches from steep unskiable terrain on all aspects, but more prominent on lee aspects.
Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid cross loaded slopes at or above treeline.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 3

Persistent Slabs

The Nov rain crust persists about 30+cm off the ground throughout the forecast area and is reactive to stability tests in the hard range. Avalanches in the upper snowpack may step down to this weakness.
Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Be aware of thin areas that may propagate to deeper instabilites.>

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

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6