Avalanche Forecast

Issued: Jan 31st, 2013 9:27AM

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

swerner, Avalanche Canada

Sea To Sky.

Summary

Confidence

Good

Weather Forecast

The offshore upper ridge will start to move onto the coast pushing the polar front to the North bringing rising freezing levels, and sunny skies. Friday: A mild SW flow will show no new precipitation and ridgetop winds will be light from the West. Alpine temperatures will rise to 3.0 degrees and freezing levels will rise to 2200 m. Expect periods of Alpine sun and solar radiation.Saturday: Continued warm temperatures and sunny skies providing a strong solar influence. Alpine temperatures will rise to 4.0 degrees and freezing levels will be near 2400 m. Ridgetop winds will be light from the SW.Sunday: Dominating ridge will start breaking down bringing light-moderate precipitation. Alpine temperatures will drop to -3.0 with freezing levels falling to 1300 m.

Avalanche Summary

Numerous natural slab avalanches size 1.0-2.5 on NE-E aspects, one being a cornice release, and others releasing on older buries surface hoar layers. Rider triggered size 1.0 on SE aspect at 1500 m on most recently buried surface hoar/crust interface. Numerous natural loose wet avalanches fromÂ steeper solar aspects up to size 1.0. With forecast rising freezing levels and a high solar influence, loose wet avalanches will continue and potentially step down and entrain most snow above the buried surface hoar/crust interface.

Snowpack Summary

The upper snowpack is showing continued settlement and gaining strength, although forecast rising alpine temperatures and sunny skies will affect and weaken the upper snowpack. Â Wind slabs are still found behind ridges, ribs and on lee slopes. Snow amounts (20-50 cm) Â sits on a Â variety of old surfaces including wind slabs, crusts and surface hoar crystals that are mainly found in sheltered locations (treeline and below, northerly aspects). This layer has been slightly touchy generally from isolated sheltered areas where the surface hoar had a chance to form. Down deeper sits another surface hoar layer (40-80 cm) which seems to be gaining strength with little to no recent reactivity on it. Below this sits a generally well settled mid pack, which may be bridging a basal facet/crust layer in deeper snowpack areas. The average snowpack depth at treeline is near 170 cm.

Problems

Wind Slabs

Recent winds have formed wind slabs in unsuspecting places (reverse loaded). Wind slabs have been touchy to rider triggers. Stiff, hollow snow below your feet is a good indicator of unstable snow. Cornices may become weak and fail with warming.

Extra caution around freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>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 of the snowpack deteriorating.

Avoid slopes when warming and solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

Buried down 20-50 cm exists a surface hoar/crust/facet layer. This layer has been reactive in sheltered locations over convex rolls and steeper terrain features.

Dig down to find and test weak layers before dropping into your line.>Whumpfing is direct evidence of a buried instability.>Use extra caution during warming and sun exposed slopes; especially if snow becomes moist or wet. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 5

Valid until: Feb 1st, 2013 2:00PM