Avalanche Forecast

Issued: Mar 22nd, 2014 10:25AM

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.

Sunny breaks on Sunday could reactivate weaknesses in the snowpack with the potential for very large avalanches.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Synopsis: The remnants of a very weak system pass over the region Saturday afternoon ahead of Sunday's strengthening ridge. A warm system approaches the coast Monday which should push high cloud into the region. There's potential for very high freezing levels on Tuesday, but its still too far out to say. There's a chance for significant precipitation on Wednesday.Sunday: Freezing Level: 900m - 1200m; Precipitation: Trace; Treeline Wind: Very light, Variable | Ridgetop Wind: Light, WestMonday: Freezing Level: 1000m; Precipitation: Nil; Treeline Wind: Light, NE | Ridgetop Wind: Light SWTuesday: Freezing Level: 1600m - 1900m; Precipitation: Trace; Treeline Wind: Light, SW | Ridgetop Wind: Light SW

Avalanche Summary

The Purcell snowpack is a strange beast at the moment. Most of the region reported no avalanche activity for the day, and yet we received reports of a widespread cycle over the last 48 hours to size 2.5 in the mountains west of Kimberely. Sounds like some of the activity was induced by natural cornice fall.We've received reports of size 2.5 and size 3 natural slab avalanches which occurred a few days ago in the Quartz Creek area. The slides occurred on southwest facing alpine terrain with solar warming as a trigger.

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 of recently buried crusts and surface hoar remain untrustworthy.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Wind Slabs

Recent accumulations have likely been blown into pockets of soft wind slab by light to moderate winds out of the SW, W and NW. Watch for triggering in gullies, and in the lee of terrain breaks and ridge crests.

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

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Mar 23rd, 2014 2:00PM