Avalanche Forecast

Issued: Jan 13th, 2013 9:01AM

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

pmarshall, Avalanche Canada

Sea To Sky.

Temperatures are forecast to rise significantly early this week. This rapid increase in temperature will result in a spike in avalanche danger. For advice on how to manage these changing conditions please refer to the latest forecaster's blog.

Summary

Confidence

Fair

Weather Forecast

Monday: Mainly sunny with valley cloud. An above freezing layer (AFL) is expected to develop between 1500 and 3000 m. Mountaintop temperatures should rise throughout the day. Winds are light from the northwest. Tuesday: Mainly sunny with valley cloud. The AFL strengthens with mountaintop temperatures climbing to at least +5. Winds are light from the northwest. Wednesday: Mainly sunny with valley cloud. The AFL will likely persist with mountaintop temperatures remaining above zero.

Avalanche Summary

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. We could see this weakness wake up this week as temperatures rise above zero in the alpine.

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 on Wednesday continued to yield easy to 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.

Avoid travelling on slopes which are becoming wet due to rain, warm temperatures, or sun.>Choose conservative lines and watch for clues of instability.>Be wary of slopes that did not previously avalanche - even on low angle terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Wind Slabs

Northerly winds have created thin pockets of wind slabs in lee and cross-loaded terrain features, while older buried wind slabs exist on exposed north facing slopes.

Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - 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.

Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>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 14th, 2013 2:00PM