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Archived

Avalanche Forecast

Mar 10th, 2013–Mar 11th, 2013
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
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
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

Confidence

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

Weather Forecast

Sunday night and Monday: A weakening front is moving across the S part of the region possibly bringing trace precipitation for Sunday evening. A ridge of high pressure is building on Monday allowing some sun and clouds, moderate W winds, and freezing levels rising to 1200 m.Tuesday: A low pressure approaches the interior which could leave light to moderate precipitation with moderate to strong winds from the SW and freezing levels rising to 1800 m.Wednesday:  Another frontal system is moving across the province which could bring more light precipitation and slightly similar mild temperatures but with lighter winds from the same direction.

Avalanche Summary

Widespread natural activity was reported on solar aspects producing size 1 loose wet avalanches on steep slopes. Some of these would have triggered wet slabs size 2 on underlying slopes. There was also report of some cornice failure, some of which pulled out size 3 slab avalanches on the underlying alpine features.  There was also report of windslabs size 1 that were triggered by sledders on windloaded shaded aspects.

Snowpack Summary

Wind slabs exist in the alpine and at treeline on lee features of recent SW and W winds. They will still be susceptible to sledder and skier triggering. Outside of wind effected areas, top snowpack is generally gaining strength and starting to bond to the underlying surfaces. The deeper surface hoar/sun crust persistent weak layer down 60-90 cm is less reactive to skier traffic but could still be triggered by a large load (like a cornice fall or a windslab avalanche stepping down). This layer remains a concern to professionals. At the surface, there is a suncrust on SE-S-SW facing slopes at all the way up in the alpine, a melt-freeze crust up to 1600 m. and some surface hoar on shaded slopes above that elevation. 

Avalanche Problems

Wind Slabs

Wind slabs have formed recently and have been sensitive to human triggering. Cornices are also very large; stay far away especially when sun comes out tomorrow.
Carefully evaluate bigger terrain features by digging and testing on adjacent, safe slopes.>Use extra caution on exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 5

Persistent Slabs

Persistent weak layers exist buried down 60-90 cm, comprising of surface hoar and a sun crust. A cornice fall could definitely trigger this layer.
Avoid big slopes that have not avalanched recently.>Choose well supported terrain.>

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

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 6