Avalanche Forecast

Issued: Mar 21st, 2014 10:03AM

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

ghelgeson, Avalanche Canada

Purcells.

Watch the temperature and solar warming this weekend, heat and/or direct sun could quickly initiate cornice fall and natural slab avalanche activity.

Summary

Confidence

Fair

Weather Forecast

Synopsis: A ridge builds into the interior this weekend making for a fairly unexciting weather weekend. Look for high cloud, moderate freezing levels and no significant precipitation.Saturday: Freezing Level: 700m - 1100m; Precipitation: Nil; Treeline Wind: Light, SE | Ridgetop Wind: Light, W/SWSunday: Freezing Level: 600m - 900m; Precipitation: Trace; Treeline Wind: Light, SW | Ridgetop Wind: Light, W/NWMonday: Freezing Level: 1200m; Precipitation: Nil; Treeline Wind: Calm | Ridgetop Wind: Light, W

Avalanche Summary

We've received reports of size 2.5 and size 3 natural slab avalanches which occurred recently in the Quartz Creek area. The slides occurred on southwest facing alpine terrain with solar warming as a trigger. Sunny breaks over the next few days will likely reactivate weaknesses in the snowpack with the potential for very large avalanches.

Snowpack Summary

Light snow accumulations overlie a well-settled storm slab which formed last weekend. Under the storm slab you'll likely find small surface hoar in shaded terrain and crusts on previously sun-exposed slopes. Recent winds have redistributed surface snow into wind slabs in exposed lee terrain. Rain from the weekend saturated the snowpack at lower elevations and the more recent accumulations may overlie a refrozen crust. Up to 95cm below the surface you may find surface hoar and crusts buried at the beginning of March. This interface is still touchy in some areas, particularly in the north of the region. The deeper facet/crust persistent weakness buried at the beginning of February, now down 60 to 160cm, has been highly variable in terms of reactivity and is still very difficult to trust. Needless to say, any avalanche at these deeper, persistent interfaces would be large and destructive.Weak basal facets exist in many areas, but without a large load, triggering now is unlikely.

Problems

Persistent Slabs

There are a number of persistent layers in the mid to upper snowpack which have professional operators concerned. These layers, which include recently buried crusts and surface hoar, continue to be touchy, especially in the north of the region.

Dig down to find and test weak layers before committing to a line.>Use conservative route selection, stick to moderate angled terrain with low consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Wind Slabs

Recent accumulations have likely been blown into pockets of wind slab by generally moderate southwest winds. Watch for triggering in gullies, and in the lee of terrain breaks and ridge crests.

Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

The deeply buried early February interface should stay on your radar as activity on this layer would be large and destructive. Possible triggers include cornice fall, thin spot triggering or solar warming.

Be aware of the potential for large, deep avalanches.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Mar 22nd, 2014 2:00PM