Avalanche Forecast

Issued: Jan 13th, 2013 9:03AM

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

South Coast.

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

Recent observations include several small skier controlled wind slabs. 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. This layer may wake up again when temperatures rise above zero this week.

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.

Avoid travelling on slopes which are becoming wet due to rain, warm temperatures, or sun.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Choose conservative lines and watch for clues of instability.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Wind Slabs

Northerly winds have produced new wind slabs in exposed lee and cross-loaded terrain, while older buried wind slabs lurk on north facing slopes at and above treeline.

Be cautious as you transition into wind affected terrain.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - 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.>Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 14th, 2013 2:00PM