Avalanche Forecast

Issued: Nov 21st, 2013 8:11AM

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

danyelle magnan, Parks Canada

Glacier.

As people start to venture further keep in mind that the snowpack is still young. Crevasses on glaciers are open or thinly bridged; rope up!

Summary

Weather Forecast

Today will be chilly, with alpine temps of -18 to -12. Moderate to strong winds at ridgetop should shift to the NW today and be reverse loading slopes. We may see a few flurries overnight and then clearing Friday and into the weekend. Fri and Sat should have alpine temps of -10 to 0, with freezing levels rising to 1500m on Sat.

Snowpack Summary

The snowpack is adjusting to the load it received earlier this week. There are several reactive storm snow instabilities, and the Nov 12 surface hoar layer, sitting ~40cm above ground, has been found in most drainages in the park. On N aspects at higher elevations, the base is likely weak where the preserved October snow facetted.

Avalanche Summary

The cold snap slowed avalanche activity. Yesterday around noon, a large natural avalanche occurred from the east facing slope below the Dome Col. It propagated the width of the slope, 100-150m wide and failed at the base of the snowpack. During the storm, widespread size 2-3.5 avalanches occurred, running well into the alder and avalanche fans.

Confidence

Due to the number of field observations

Problems

Storm Slabs

The snowpack is still adjusting it's new load. This cold snap has made it less reactive but as things warm up over the next few days the various storm slab instabilities and the underlying surface hoar layer may wake up.

Choose well supported terrain without convexities.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Wind Slabs

Windslabs are less widespread, as the cold temps help to soften them. Expect windslabs at ridgecrests and on lee slopes due to continued moderate to strong SW winds. The winds are forecast to shift to the NW today and will reverse load slopes.

Be cautious as you transition into wind affected terrain.Assess start zones carefully and use safe travel techniques.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Valid until: Nov 22nd, 2013 8:00AM