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Archived

Avalanche Forecast

Mar 9th, 2013–Mar 10th, 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
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
1: Low
The avalanche danger rating below treeline will be low

Regions: Purcells.

Confidence

Fair - Track of incoming weather is uncertain

Weather Forecast

Saturday night and Sunday: Winds will pick up as the next system is moving in but precipitation will not be as much as forecasted yesterday. Expect just light precipitation starting late during the day with moderate to strong winds from the W.  Freezing levels should still rise to 1300 m. but solar radiation will be much less than Saturday.Monday:  Trace precipitation amounts (light amounts over the S part of the region) are expected with mostly cloudy skies, moderate W winds and slightly cooler temperatures and lower freezing levels. Tuesday: Timing and track of the next system is still uncertain, but there is a potential for a fairly active system that could deliver interesting amounts of precipitation.

Avalanche Summary

3 natural slab avalanches size 3 were reported that would have been triggered by solar radiation on S and SE aspects. Smaller loose wet and dry avalanches were reported out of steep terrain on all aspects. There was also an observation of a large cornice failure on a N aspect which did not trigger a slab on the slope below.

Snowpack Summary

New windslabs are expected to form on lee features of forecasted moderate W winds in the alpine and below ridgetops at treeline. Older windslabs also exist in the alpine which were formed by the N winds yesterday. These will be susceptible to sledder and skier triggering. 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 of the snow, expect to find a suncrust on SE-S-SW facing slopes at all elevations (especially on steep slopes), a melt-freeze crust all the way up to 1600 m. and possibly some surface hoar on shaded slopes above that elevation.

Avalanche Problems

Wind Slabs

Old wind slabs have formed recently and new wind slabs will form tomorrow. They will most likely be sensitive to human triggering.
Be extra careful on lee and cross-loaded terrain near ridge crests.>Carefully evaluate bigger terrain features by digging and testing on adjacent, safe slopes.>

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.>Be aware of the potential for very large avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 2 - 6