Boletín de aludes

Purcells

Mar 25 – 26, 2012Avalanche Canada
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Archivado · caducó 15 years ago

Peligro de aludes

Tue
Wed
Alta montaña
3 · Notable
Límite del bosque
3 · Notable
Bajo el límite
3 · Notable
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Lo esencial

There is a possibility of higher than forecast freezing levels combined with precipitation that might be rain. If it is raining above 1500 metres in your area, then the danger ratings may be closer to HIGH.

Problemas de aludes

  • Cornices

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–4
    Large cornices are looming above many slopes. These may weaken with fluctuating temperatures and could act as a trigger for a very large avalanche. Variable wind slabs can also be found behind ridges and terrain breaks.

  • Loose Wet

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Likely
    Tamaño
    1–5
    Previous solar warming may not get a chance to recover overnight. Forecast rain up to about 1400 metres may weaken the snowpack. Loose wet releases at treeline may step down to the deeply buried weak layer.

  • Deep Persistent Slabs

    • Alta montaña
    • Límite del bosque
    • Bajo el límite del bosque
    Probabilidad
    Possible - Likely
    Tamaño
    4–8
    Very large avalanches have been failing on a weak layer up to 2 m deep with alarming ease. This problem demands respect. Choose very conservative terrain, as the consequences of triggering this layer could be huge.

Snowpack Summary

Warm alpine temperatures combined with strong solar radiation on Sunday caused moist snow up to about 2400 metres. The major concerns are the mid-February persistent weak layer, buried 1-2 m deep, and facets at the base of the snowpack. The February layer demands respect right now. It is very touchy and can be triggered remotely or by a light load on a variety of aspects, creating frighteningly large avalanches.

Avalanche Summary

A natural cornice fall size 2.5 was reported from the high alpine on a NW aspect on Saturday. On Friday, a very large avalanche was triggered by a cornice in Gorman Lake (Dogtooth Range). It was wide, deep and covered sled tracks. Photos here: https://bit.ly/GMOYCv . There have been four other close calls in the Purcell Mountains this week, all involving very large slabs releasing either from a distance or with a light load. On Thursday, a snowmobiler remotely triggered a size 3.5 slab on an east aspect at 2400m at Oldman Creek, east of Quartz Creek (video here https://bit.ly/GLHIbg). It failed 1-2 m deep, was 200-300 m wide and ran full path, taking out mature timber. A second slope also failed, either remotely or sympathetically.

Confidence

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

Weather Forecast

High cloud moved across the region on Sunday afternoon that limited the extent of solar warming, but trapped warm air beneath the cloud layer that raised the alpine temperatures to near zero. The freezing level is expected to drop down to near valley bottom by Monday morning. A moist system is forecast to move north from south of the border on Monday morning. Some models show a narrow band of precipitation and warm air moving up into the Purcells. If this happens, the region may see 20-25 cm of snow at higher elevations, and rain below 1400 metres. Tuesday should continue to be unsettled as southwest winds increase during the day and the freezing level stays at about 1500 metres. Precipitation should start again on Wednesday morning and build to heavy by evening.

Regiones cubiertas