Avalanche Forecast

Issued: Nov 16th, 2015 8:09AM

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

andrew jones, Parks Canada

Glacier.

New snow needs time to stabilize. Human triggering of avalanches remains likely as we head into another storm cycle.

Summary

Weather Forecast

A brief period of high pressure subsides this afternoon as a storm front tracks into the region. Moderate SW winds will build to strong at ridge top with a daytime hight of -4. Precipitation will begin late this afternoon bringing up to 20cm of snow by tuesday morning. Tuesday morning brings 40mm of precipitation and freezing levels up to 1400m.

Snowpack Summary

80cm of recent storm snow remains unconsolidated in sheltered areas. The November 11 surface hoar layer is present above 1800m with localized distribution. Wind slabs have developed on lee features from strong S-SW winds. Rain was observed to 1650m yesterday. A strong overnight refreeze has created a crust at lower elevations.

Avalanche Summary

Morning precipitation and warmer temperatures contributed to a natural avalanche cycle yesterday. Several avalanches from steep terrain were observed in the highway corridor, running up to size 2.5 with moist debris terminating halfway through their run-out zones.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Storm Slabs

Yesterday's warmer temperatures encouraged the development of widespread storm slabs. These slabs will be easily triggered where they overlie localized areas of surface hoar buried 50-80cm.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Wind slabs have formed on alpine lee slopes. These slabs reach further down slope due to strong S-SW winds on Friday. Slabs may sit on top of the Nov 11 surface hoar layer. These slabs will be sensitive to triggering.

Use caution in lee areas. Recent wind loading have created wind slabs.Watch for whumpfing, hollow sounds, and shooting cracks.

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

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 3

Deep Persistent Slabs

Recent natural avalanches have been triggered on this layer. In the right location, this layer can be triggered by the weight of a person. When triggered, these avalanches will be large with serous consequences.

Carefully evaluate and use caution around thin snowpack areas.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Nov 17th, 2015 8:00AM