Avalanche Forecast

Issued: Feb 17th, 2012 9:48AM

The alpine rating is considerable, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs, Deep Persistent Slabs and Cornices.

Avalanche Canada jfloyer, Avalanche Canada

I suspect considerable danger will feel a bit on the high side for areas to the east that are likely to see less snow.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Saturday

Weather Forecast

By the end of Saturday, western parts of the region could see up to 15 cm of low density new snow as a frontal system tracks along the US/Canadian border. Eastern parts will see more in the region of 5 cm. Moderate southwest winds are expected and alpine temperatures should hover between -5 and -10C. For Sunday and Monday, a series of weak disturbances embedded in a northwesterly flow will bring flurries or very light precipitation. Winds should be generally light or moderate, with the switch from southwesterly to northwesterly expected to occur on Sunday night.

Avalanche Summary

No recent avalanches have been reported from this region. Deep persistent slab avalanches remain possible in isolated terrain features; i.e. heavy triggers in shallow rocky snowpack areas on unsupported slopes. Check out the Avalanche Image Gallery under the Library tab for some photos of last weekends deep persistent slab avalanche cycle.

Snowpack Summary

"Dust on a crust" on southerly aspects, where recent sunshine formed a crust that has since been buried by light snow. Shady slopes do not have this crust. Cool alpine temperatures are promoting facet growth in the upper snowpack keeping the surface snow fairly soft. Just a few cm of recent snow now sits on a variable weak layer comprising surface hoar (most likely in the west of the region), sugary facets on shady N'ly and sun crusts on solar aspects. These interfaces need watching as they receive more snow load and/or wind slab builds on top of these surfaces. Below that, approximately 20 cm of near-surface facets can be found on shady slopes. While the mid-pack is quite strong in most locations, basal facets remain a concern on shady alpine slopes that did not avalanche in the last cycle. Data that supports this lingering concern includes recent professional observations that found easy to moderate compression test results with a sudden "drop" fracture down 80 and 100 cm in a location with a 160 cm snowpack.

Problems

Wind Slabs

An icon showing Wind Slabs
only developing problem - still low consequence

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Deep and destructive persistent slab avalanches are unlikely, but a large trigger may activate this weakness on a steep, rocky & unsupported area with a shallow snowpack.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely

Expected Size

3 - 6

Cornices

An icon showing Cornices
Cornices are large, unsupported and may be a trigger for a large avalanche on the slope below.

Aspects: North, North East, East.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Valid until: Feb 18th, 2012 9:00AM

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