Avalanche Forecast

Issued: Mar 17th, 2012 4:00PM

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

mike.koppang, Alberta Parks

Kananaskis.

20cm of new snow overnight on Friday/Saturday. Conditions are improving but this is not the time to push into bigger terrain. Conservative routes and decision making is essential at this time.

Summary

Confidence

Good

Weather Forecast

No new snow expected over the next 24hrs. Winds are forecast to be light out of the south and temperatures around -8C at treeline during the middle of the day. Cloudy conditions will persist and visibility into alpine areas will be limited.

Avalanche Summary

1 size 3 Na on a steep (40-45deg) NE aspect at 2800 near Black Prince. 300m wide, up to 1.5m deep failing in the storm snow layers, as well as stepping down to the Valentines day crust as well as ground in some of the steeper rocky areas. 1 size 3 Na on a N aspect on the Rundle bowls above the Canmore Nordic Center. Slide ran full path, stopping at the end of its historical trim lines. No other information available on this due to limited visibility. 2 other size 2 avalanches were also observed on N and E aspects at 2600m. Both of these slides occurred in steeper unsupported terrain failing within the storm snow and stepping down to the Valentines day interface.

Snowpack Summary

An additional 20cm of new snow fell overnight. Over the past 72hrs, up to 50cm of new snow has fallen under the influence of a light to moderate SW flow. The Valentines day surface hoar layer is now buried down up to 160cm and is becoming more stubborn to trigger. Propagation saw tests are showing that if this layer is triggered it will propagate across a terrain feature but it is becoming less reactive to light loads such as a skier. On solar aspects the March 10th temperature crust is down 50-60cm on solar aspects. A thin layer of weak facetted crystals is developing on top of this crust and the bond between the new snow and the underlying crust should be carefully evaluated. Any avalanche initiated in the upper snowpack will likely step down to the Valentines day interface so skiers should keep this on their mind as they travel.

Problems

Storm Slabs

Light to Moderate SW winds are creating slabs up to 40cm thick within the storm snow in open areas at treeline and above. These Slabs are most evident on N and E aspects as well as on crossloaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Persistent Slabs

Surface hoar buried up to 160cm continues to be a major concern in the snowpack. A dense slab now sits on top of this layer. Avalanches in the upper snowpack will likely step down to this layer causing a destructive avalanche.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 6

Persistent Slabs

The March 11th Temperature crust is buried down 50cm on solar aspects. The bond of the upper snowpack to this crust is highly variable and requires careful evaluation as you travel.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Cornices have grown significantly in the alpine. Failures continue to occur and have triggered avalanches up to size 3 on the underlying slopes. Give cornices a wide berth and stay well back from corniced ridge crests.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

2 - 7

Deep Persistent Slabs

The weak basal facets and depth hoar have re-awakened. Large terrain features are areas of concern where a smaller slide could step down and trigger a very large avalanche with deep and wide propagation.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 7

Valid until: Mar 18th, 2012 9:00AM