Avalanche Forecast

Issued: Jan 11th, 2013 8:37AM

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

ghelgeson, Avalanche Canada

South Rockies.

Current avalanche conditions are complex. Stay very cautious in your approach to the mountains this weekend.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

Saturday: Light winds out of northwest. Freezing level at valley bottom. No significant snowfall. 1500m temp: -10Sunday: Light ridgetop winds out of the N increasing to moderate NW after lunch. Freezing level at valley bottom. No significant snowfall. 1500m temp: -10Monday: Strong NW winds at ridgetop. Freezing level at valley bottom. Isolated flurries, no significant accumulation.Tuesday: Freezing level forecast to rise to 2000m

Avalanche Summary

Our field team reported numerous small avalanches on Thursday from the Inverted Peak area. In the nearby Lizard Range avalanches were intentionally triggered by skiers and explosives resulting in avalanche to size 2 on all aspects. I suspect a thorough look around the South Rockies would reveal a similar pattern.

Snowpack Summary

The South Rockies snowpack is fairly complex at the moment. Here's the highlights: Around 50 cm of storm snow fell in favored locations earlier this week. This snow rests on a myriad of old surfaces (January 4th interfaces) that include sun crust on steep south and west facing terrain, surface hoar in sheltered locations at treeline and below and facets everywhere else. We don't have a good handle on exactly where the surface hoar is and is not. As a result, you need to dig frequently to confirm the presence or absence of surface hoar/sun crust/facets on individual slopes if you're thinking about jumping into complex or challenging terrain.The wind during the storm was primarily out of the SW, but the winds have been all over the map since then. As a result I'm suspect of wind slabs on all exposed slopes at and above treeline. The midpack is well settled and strong with one or two (location specific) crusts deep in the snowpack. These crust/facets combos are largely dormant, with the only concern being triggering from a shallow snowpack area or with a heavy trigger.

Problems

Persistent Slabs

50 cm of settled storm snow rests on a variety of weak surfaces. These weaknesses are MOST PRONOUNCED AT AND BELOW TREELINE. The trees are not the safe haven they usually are.

Be wary of slopes which have not previously avalanched. It may be challenging to determine what has slid due to recent wind loading.>Avoid convex rolls and terrain traps.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 6

Wind Slabs

Shifting winds have formed wind slabs 15 - 100 cm in depth on all aspects in the alpine. While I see it as a low probability occurrence, a shallow avalanche or cornice fall has the potential to step down and trigger a larger avalanche.

Thinking of heading into challenging/complex terrain? You need to carefully assess each slope you're thinking of riding. If you don't know how to do this, it's a good time to stick to simple terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>