Avalanche Forecast

Issued: Nov 27th, 2012 9:33AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs and Persistent Slabs.

jlammers, Avalanche Canada

South Columbia.

Summary

Confidence

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

Weather Forecast

Wednesday will see mostly cloudy skies with moderate snowfall occurring throughout Thursday and Friday. Winds will be moderate to strong from the west on Wednesday switching to strong and southwesterly for Thursday and Friday. Freezing levels should remain at about 1200m for the forecast period.

Avalanche Summary

Reported avalanche activity has been limited to size 1 and 2 loose snow avalanches out of steep, sun-exposed terrain.

Snowpack Summary

Snow accumulations from last week varied from 25-50 cm, although the resulting storm/wind slabs have most likely gained considerable strength with the more recent break in the weather.A buried surface hoar layer has been reported. Although I am unsure of its distribution throughout the region, the average depth is about 70 cm from the surface and seems to exist in specific, sheltered locations. Below this (down 80-110 cm) sits the early November crust. Test results on this layer have been variable; however, some have shown sudden planar pops on facetted crystals at this crust interface, or within the crust sandwich.Now is the time to take stock of what surface conditions may be developing in your area (surface hoar, sun crusts on steep solar aspects). Consider how these conditions will affect the snowpack once new snow arrives over the next few days.The snowpack depth in the alpine ranges from 130-225 cm. Treeline near 150 cm. A sharp transition exists below treeline, where the snowpack peters out around 1300 m.

Problems

Storm Slabs

Although last week's snow has had time to gain considerable strength, triggering storm/wind slabs may still be possible in steep, unsupported terrain. As well, forecast winds for Wednesday may be enough to create reactive new wind slabs.

If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.>Use caution around freshly wind loaded features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Persistent Slabs

There is a faceted crust that exists in the lower snowpack. Although no recent avalanches have been reported on this layer, triggering seems most likely on unsupported terrain at higher elevations or within start zones with smooth ground cover.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Nov 28th, 2012 2:00PM