Avalanche Forecast

Issued: Jan 12th, 2013 8:42AM

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

Avalanche Canada pmarshall, Avalanche Canada

Summary

Confidence

Good

Weather Forecast

Sunday: Mainly sunny with cloudy periods in the afternoon. Temperatures should remain cool with alpine highs near -8. Winds are moderate from the northwest. Monday: Mainly sunny. An above freezing level develops through the day between 1500 and 2500 m. Winds are moderate to strong from the northwest. Tuesday: Mainly sunny. The above freezing layer strengthens with alpine temperatures rising to +5. Winds are moderate to strong from the northwest.  

Avalanche Summary

There are no new reports of natural or human triggered avalanches in the region. However, 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 also present in this region.

Snowpack Summary

Up to 15 cm of low density new snow sits on the previous 40-80 cm of storm snow from earlier in the week. Northerly outflow winds have produced pockets of new wind slabs in south facing terrain, and old dense wind slabs lurk below the surface on northerly aspects. A layer of surface hoar, facetted snow, and /or a crust exists at the base of the recent storm snow. Snowpack tests show that this interface is susceptible to human triggering and has the 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

An icon showing Persistent Slabs
Up to 80 cm of snow sits on a weak layer consisting of surface hoar, a crust, and/or sugary facets. This weakness may be triggered by light loads, from a distance, and in relatively low angle terrain.
Be wary of slopes that did not previously avalanche - even on low angle terrain.>Choose conservative lines and watch for clues of instability.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Wind Slabs

An icon showing Wind Slabs
Northerly winds have produced new wind slabs in exposed lee and cross-loaded terrain, and older buried wind slabs are lurking on north facing slopes at and above treeline.
Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Jan 13th, 2013 2:00PM

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