Avalanche Forecast

Issued: Feb 25th, 2013 10:11AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Tuesday: Light snowfall / Light northwest wind / Freezing level at 900mWednesday: Light snowfall/ Light west winds / Freezing level at 900mThursday: Light to locally moderate snowfall/  Moderate south winds / Freezing level at 800m

Avalanche Summary

On Sunday a skier remotely triggered a size 2 slab avalanche from 40 metres away. The avalanche, which occurred on a north aspect at 2000m, failed on the February 12 surface hoar. On Monday numerous deep size 2 avalanches were triggered off small rolls in a popular sledding area. These avalanches were also triggered on the February 12th surface hoar. These events speak to the touchy nature of the persistent avalanche problem. I would expect human triggering at this deep persistent interface to be a very real possibility throughout the week.

Snowpack Summary

Moderate to locally heavy snowfall on Sunday adds to ongoing potent storm instabilities which seem to be most reactive as a wind slab in exposed terrain or as loose snow in more sheltered areas. A weak surface hoar layer which was buried on February 12th now exists up to a metre below the surface in many places. The touchy and destructive nature of this persistent weakness remains a primary concern for professionals in the region. This interface has also shown reactivity on southerly aspects where a sun crust also exists. The mid to lower snowpack are generally strong and well settled. I anticipate significant cornice growth with the current weather pattern, and expect them to be weak and potentially destructive.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Numerous large avalanches are failing on a weak and reactive layer of surface hoar which now lies up to 100cm below the surface. Triggering this weakness may result in surprisingly large avalanches.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid exposure to overhead avalanche terrain, as large avalanches may reach the end of runout zones.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Storm Slabs

An icon showing Storm Slabs
Snow and wind on Sunday night adds to an ongoing storm instability. Watch for increased slab reactivity in wind-affected terrain. In sheltered areas, the new snow may also react as a loose dry avalanche.
Be cautious as you transition into wind affected terrain.>Be cautious of sluffing in steep terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 5

Valid until: Feb 26th, 2013 2:00PM

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