Avalanche Forecast

Issued: Jan 14th, 2013 9:02AM

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

pmarshall, Avalanche Canada

South Coast.

Alpine temperatures are forecast to climb to +10 on Tuesday! Check out the latest forecaster's blog post for advice on how to manage these changing conditions.

Summary

Confidence

Fair

Weather Forecast

Tuesday: Mainly sunny with patchy valley fog. The above freezing layer (AFL) is expected to strengthen with temperatures rising to near +10 in the alpine. Winds are moderate from the northwest. Wednesday and Thursday: A mix of sun and cloud with valley fog. The AFL persists between 1000 and 2500 m, but temperatures should cool slightly. Winds are light to moderate from the northwest.

Avalanche Summary

Recent observations include several small natural and skier triggered wind slabs up to 20 cm deep from steep lee terrain. There was an accidentally triggered size 2 avalanche in the Spearhead Range near Whistler on Thursday. A thin wind slab was triggered near ridge top, which stepped down to a buried weak layer approximately 100 cm deep further down the slope. This event was suspected to have released on the early January surface hoar layer, which is present in this region as well.

Snowpack Summary

The snow surface consists of thin new wind slabs, a sun crust, dry snow, or feathery surface hoar depending on aspect and elevation. Below this 40-80 cm of settling storm snow sits on a layer of surface hoar, facetted snow, and /or a crust. Recent snowpack tests show that this interface is gaining strength but is likely still susceptible to human triggering with potential to propagate widely. No significant weaknesses have been reported recently below this in the mid snowpack layers. Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in steep, shallow, rocky terrain where more facetting has taken place..

Problems

Persistent Slabs

A buried weakness, down 40-80 cm, could wake up as temperatures rise above zero early this week.

Be wary of slopes that did not previously avalanche - even on low angle terrain.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Wind Slabs

Strong northerly winds have produced new wind slabs in exposed lee and cross-loaded terrain.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Loose Wet

Loose wet activity is expected as temperatures rise. A loose wet slide could step down and trigger weaknesses deeper in the snowpack.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 15th, 2013 2:00PM