Avalanche Forecast

Issued: Jan 14th, 2013 8:51AM

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

Sea To Sky.

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

Summary

Confidence

Fair

Weather Forecast

Tuesday: Mainly sunny with 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

There are no new reports or observations of natural or human triggered avalanches from the past 2 days, and I suspect there were a lot of people in the mountains on the weekend. There was a size 2 accidentally triggered slab avalanche in the Spearhead Range on Thursday. A thin wind slab was triggered near ridge top on a relatively low-angle slope, which then stepped down to a weak layer approximately 100 cm deep lower on the slope. This avalanche is suspected to have released on the early January surface hoar layer.

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 40-70 cm of storm snow sits on a weak layer of surface hoar, facetted snow, and/or a crust. Snowpack tests continue to yield moderate sudden planar, or "pops", results on this interface. 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

Warm temperatures and solar radiation will increase the probability of avalanches releasing on a buried weak layer of surface hoar, facets, and/or a crust, down 40-70 cm.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Wind Slabs

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

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 early this week. 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