Avalanche Forecast

Issued: Dec 25th, 2013 8:16AM

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

danyelle magnan, Parks Canada

Glacier.

Merry Christmas! We might be in for a series of big storms. If and when they hit, avalanche danger will rise rapidly.

Summary

Weather Forecast

A series of Pacific frontal systems will pass through the region over the next 3 days, with the heaviest snowfall amounts likely north of the highway. Strong westerly winds will intensify loading rates. Expect mild temps, with the possibility of an above freezing layer from 1500m to 2500m developing overnight.

Snowpack Summary

Up to 80cm of settled snow overlies the Dec 8 PWL, which is surface hoar at lower elevations and facets and variable wind slabs at higher elevations. This layer is becoming less reactive in tests. The lower snowpack is facetted, with 2 PWL's in the lower 50cm, that are slowly gaining strength. SW winds have formed windslabs above treeline.

Avalanche Summary

Natural slab avalanches continued occurring yesterday, even after it stopped snowing, triggered by ongoing wind-loading. They occurred from all aspects on both sides of Rogers Pass, from elevations from 2700m to 1800m, and were size 2-2.5. Several ran into the avalanche paths, moving fast and picking up mass at lower elevations.

Confidence

Intensity of incoming weather systems is uncertain

Problems

Wind Slabs

SW winds yesterday have lots of loose snow available to load onto lee slopes and form soft windslabs above treeline. Pockets of windslab have been reactive to skiers. Use extra caution on lee and cross loaded terrain particularly near ridge crests

Be cautious as you transition into wind affected terrain.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Storm Slabs

40cm of recent storm snow is settling. Within this slab are layers of large, weak snowflakes that may be triggered by skiers/riders.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

The interface between the December snow and the facetted November snow, down ~80cm is the biggest concern. Although this interface is becoming less likely to trigger it is possible, or smaller avalanches may step down to this layer.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Dec 26th, 2013 8:00AM