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Archived

Avalanche Forecast

Jan 15th, 2012–Jan 16th, 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
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: Purcells.

Confidence

Fair - Due to variable snopack conditionsfor the entire period

Weather Forecast

SUNDAY: Light precipitation with light winds from the west. Temperatures dropping to -15 degrees celsius. MONDAY: Light precipitation with continued cold temperatures. Winds moderate from the west. TUESDAY: Continued light precipitation and cold temperatures.

Avalanche Summary

Recent reports indicate human triggered avalanches to size 1.5 on windslabs in the alpine and at treeline. Explosives testing in the southern portion of the region indicates (size 3.5 on a north aspect at 2700m with 200cm fracture) that avalanches are capable of stepping down to deep basal facets with heavy loads. Cornices have also been failing and could be a heavy trigger for wind and persistent slabs on the slope below.

Snowpack Summary

5-15cm of dry new snow combined with wind has encouraged slab development and cornice growth. This new snow now sits on a variety of surfaces (facets, surface hoar in sheltered areas, wind crust, soft slabs and hard slabs).The mid-December surface hoar/facet persistent weakness, down 40cm on the eastern side of the range and as deep as 150cm on the western side, is generally producing anywhere from easy (where it's shallow) to hard (where it's deeper) test results. But all tests consistently show a high propensity to propagate fractures. Check out this YouTube video posted by the Panorama ski patrol of an ECTP2 down around 40cm on surface hoar: https://www.youtube.com/watch?v=1_NQns2Nuh0. Basal facets remain a concern for human triggering in shallow snowpack alpine areas. When these persistent weaknesses are combined with weak wind slabs, thin trigger points, and other weaknesses within and under the recent storm snow, the result is a highly variable snowpack with the potential for deep slab avalanches, especially from heavy, thin spot, and/or step-down triggers.

Avalanche Problems

Wind Slabs

New snow and wind have created new windslabs and buried recently formed ones.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Persistent Slabs

Most concerning on steep, unsupported slopes, in open glades glades.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 3 - 5

Deep Persistent Slabs

Susceptible to human triggers particularly from thin spots on slopes with variable snow distribution, heavy impacts, or deep penetration. If triggered, slabs are likely to release across entire bowls producing highly destructive avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6