Avalanche Forecast

Issued: Jan 30th, 2013 10:03AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

A ridge of high pressure seems to be dominating the pattern for the next few days. Weak systems embedded in the flow will bring light amounts of precipitation and a mix of sun and cloud. The ridge will be moving onto the coast Friday bringing sunshine and rising freezing levels.Thursday: Snow amounts near 10 cm for the Coquihalla, with few flurries up on the Duffy, accompanied by moderate-strong Westerly ridgetop winds. Alpine temperatures near -1.0 with freezing levels rising 1400 m. Friday: Mainly sunny with some upper cloud. No precipitation and ridgetop winds blowing light from the SW. Alpine temperatures rising to 2.0 degrees with freezing levels around 2100 m. Saturday: Mainly sunny possible clouds in the afternoon and no precipitation. Ridgetop winds light from the SW. Alpine temperatures near 0.0 degrees and freezing levels rising to 2300 m.

Avalanche Summary

Several rider triggered slab avalanches were initiated on NE-E aspects above 1900 m, all classified as sizze 1.0. The failure plane being the surface hoar/crust/facet layer down 20-40 cm, which has now been buried for a week.

Snowpack Summary

Up to 30 cm of snow fell over the past few days with light to moderate winds. This snow seems to be settling and gaining strength although wind slabs are possible behind ridges and ribs and may be touchy to rider triggers. Wind slabs could also be found in unsuspecting places due to changing winds from SW-NW. Be cautious of cross-loaded terrain features. The new snow has buried a variety of surfaces including old wind slabs, crusts and large surface hoar crystals which can be found in sheltered terrain below treeline. The most recent buried crust/surface hoar down approx. 10-30 cm are producing moderate-sudden planar and resistant test results, and should remain a layer to watch. Down deeper sits another surface hoar layer (40-80 cm) which seems to be gaining strength.Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in unsupported, shallow, rocky terrain where more faceting has taken place.

Problems

Wind Slabs

An icon showing Wind Slabs
New snow has been blown behind ridges and ribs with switching winds and may be rider triggered. This is a less typical pattern so east and south facing slopes as well as cross-loaded features are more suspect.
Avoid freshly wind loaded features.>Use extra caution on lee and cross-loaded terrain near ridge crests.>Assess start zones carefully and use safe travel techniques.>

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
Buried down 30-60 cm exists a surface hoar/crust/facet layer. This layer of concern seems to be most reactive in sheltered locations over convex rolls and steeper terrain features.
Whumpfing is direct evidence of a buried instability.>Dig down and see if the weak layer exists and is reactive before dropping into your line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 31st, 2013 2:00PM

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