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Avalanche Forecast

Feb 1st, 2013–Feb 2nd, 2013
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Coast.

Rising temperatures and intense solar radiation is the driving force for the Avalanche Danger Ratings on Saturday.

Confidence

Good

Weather Forecast

Saturday: The dominating ridge of high pressure will bring significant warming and sunny skies. Alpine temperatures could get as high as plus 3.0 degrees with freezing levels rising near 2300 m and sunny skies. Ridgetop winds will be light from the SW.Sunday: The ridge will start to weaken, allowing the next frontal system to move in. Skies will generally be cloudy and no significant precipitation is expected. Alpine temperatures will fall to -3.0 and freezing levels will be near 1100 m. Ridgetop winds will blow moderate from the SW.Monday: Unsettled conditions with snow amounts up to 5 cm. Ridgetop winds will be light from the SW. Alpine temperatures near -4.0 and freezing levels hovering at 1600 m in the afternoon.

Avalanche Summary

A natural size 2 slab avalanche was reported from the Southern part of the region. No additional information besides the size. On Thursday, reports from the Northern parts of the region, saw a natural slab avalanche size 2.5 from an East aspect at 2000 m, failing on the buried surface hoar layer from early January. This layer has been fairly quiet recently, goes to show it may still be reactive in isolated areas. Another noted size 2.0 slab avalanche failed on the recent buried weakness from a NNW aspect around 1600 m.Several rider triggered slab avalanches up to size 2.0 have been reported south of the Coquihalla. These avalanches were triggered from SE-E aspects  at 1600-1700 m, failing on the most recently buried crust/surface hoar/facet layer.

Snowpack Summary

Wind slabs may be found on lee slopes (N-SW) behind ridges and ribs and may be touchy to rider triggers. This recent snow seems to be settling and gaining strength although forecast rising alpine temperatures and sunny skies will affect and weaken the upper pack.Down 10-30 cm sits a persistent interface comprising of crusts, facets and surface hoar crystals. Recently, this layer has been touchy in sheltered areas at treeline and below (where the surface hoar had a chance to form). Tests done on this layer have produced moderate-sudden planar and resistant planar results. This layer should remain on your radar through the weekend. Down deeper sits another surface hoar layer (40-80 cm) which seems to be gaining strength with very little reactivity on it.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.

Avalanche Problems

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. Cornices may become weak with warming.
Use ridges or ribs to avoid pockets of wind loaded snow.>Use extra caution on lee and cross-loaded terrain near ridge crests.>Pay attention to overhead hazards like cornices.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Loose Wet

Warming and the effects of solar radiation will likely weaken the upper snowpack and produce loose wet avalanches. Natural avalanches and snowballing are obvious indicators of the snowpack deteriorating.
Avoid slopes during warming and high solar radiation, especially if the snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

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. This layer may become more reactive with warming.
Dig down to find and test weak layers before committing to a line.>Whumpfing is direct evidence of a buried instability.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 5