Avalanche Forecast

Issued: Feb 18th, 2012 10:27AM

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

Avalanche Canada jfloyer, Avalanche Canada

Summary

Confidence

Fair - Wind speed or direction are uncertain for the entire period

Weather Forecast

A moist, northwesterly airflow has set up over the region, bringing a series of weak pulses of precipitation over the next few days. Very light snowfall, around 2 cm is expected each day for Sunday, Monday and Tuesday. Freezing levels from now until Tuesday afternoon will hover between 500-1000 m. Moderate to strong westerly or northwesterly winds are expected.

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

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

Wind Slabs

An icon showing Wind Slabs
Light snow with moderate winds has developed wind slabs in isolated areas.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

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 - 5

Valid until: Feb 20th, 2012 9:00AM

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