Avalanche Forecast

Issued: Dec 10th, 2013 8:38AM

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

Avalanche Canada triley, Avalanche Canada

The new storm is expected during the day. Danger levels are expected to increase during the storm. These danger ratings may be a little high for the morning unless the storm comes early.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Overnight and Wednesday: A strong frontal system is expected to move into the region from the Northwest during the day and bring 15-20 cm by evening. Strong West-Northwest winds are expected during the storm and the temperature should rise, but the freezing level should remain at valley bottom.Thursday: Continued moderate precipitation bringing another 10-15 cm. Temperatures continue to rise slightly and moderate Westerly winds continue.Friday: Light precipitation and moderate Northwesterly winds.

Avalanche Summary

Expect increased sluffing of dry surface snow and near surface facets before the new storm snow arrives. The new storm snow may become easy to trigger where it is sitting on buried surface hoar and/or wind crusts.

Snowpack Summary

A new storm is forecast to add moderate new snow amounts above the dry cold surface snow that recently buried the very cold and facetted snow that was on the surface during the arctic outbreak. There is a great deal of variation in the snowpack with respect to elevation and exposure to winds. Shallow snowpack areas may be weak and facetted, and may not support the additional load of storm snow. The old storm snow (~30-50cm) overlies the late-November interface which typically consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. These weak layers are expected to be persistent, although in many areas the upper slab is not yet stiff enough for slab avalanches. When temperatures rise, and we get additional snow, expect this interface to become more reactive.

Problems

Storm Slabs

An icon showing Storm Slabs
The new storm should develop during the day and avalanche danger is expected to increase. New snow may make it difficult to notice wind slabs left from the recent Northerly winds.
Minimize exposure during periods of heavy loading from new snow, wind.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

An icon showing Persistent Slabs
The added load of new storm snow may allow for easy triggering of buried surface hoar where the snow above has settled into a cohesive slab.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Use extra caution around convexities or large unsupported slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Dec 11th, 2013 2:00PM

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