Avalanche Forecast

Issued: Dec 24th, 2012 9:17AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Due to limited field observations

Weather Forecast

The previous unsettled weather pattern has taken a turn. A weak high pressure system builds in the wake of the approaching Pacific Frontal system bringing light snowfall amounts later in the afternoon on Christmas day.Christmas Day: Cloudy, with snow amounts near 5 cm accompanied by light Southerly ridgetop winds. Alpine temperatures near -11 and freezing levels at valley bottom through the forecast period.Wednesday: Cloudy with a trace of snow. Ridgetop winds moderate from the West and alpine temperatures near -10.Thursday: Scattered cloud and dry. Ridgetop winds light from the West and alpine temperatures near -12.

Avalanche Summary

On Sunday, explosive avalanche control initiated a loose snow avalanche size 1.5. Numerous skier controlled size 1.0 loose snow avalanches were also triggered  on North-East aspects.

Snowpack Summary

The average storm slab depth is approximately 20 to 50 cm, and may be sensitive to rider triggers; especially in areas of wind effect on lee slopes and behind terrain features (spines, gullies, ridgelines). The most recent storm snow is low density and showing a poor bond (sluffing) on steeper terrain features. A large enough sluff may have enough force to push you around or even bury you, beware of terrain traps below you. Two crusts have been identified in the snowpack: one close to the ground that formed in early November and one around 90-110 cm below the surface, which formed in early December. At this point in time the Nov. crust seems to be dormant. Recent snowpack tests done on the December crust from the Harvey Pass Riding Area showed a moderate compression test failure, with a sudden collapse characteristic. Testing on that layer showed inconsistent results, but I feel value is there to keep that layer in the back of your mind. It may be stubborn to trigger, but the result would be a consequentially large avalanche. The mid pack is generally strong and well bonded.

Problems

Storm Slabs

An icon showing Storm Slabs
Recent storm snow has set up a storm slab on all aspects and may be touchy to rider triggers. Recent S-SW winds have transported storm snow into thicker slabs,, especially behind spines, entrances to gullies and on lee N-E slopes.
Whumpfing, shooting cracks and recent avalanches are all strong indicators of an unstable snowpack.>Be cautious as you transition into wind affected terrain.>The best powder will be found in sheltered locations from the wind.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Dry

An icon showing Loose Dry
Loose dry snow remains unconsolidated in areas that is protected from the wind. Sluffing may entrain enough snow to bury a rider, or push you into a consequential terrain trap.
Be cautious of sluffing in steep terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Dec 25th, 2012 2:00PM

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