Avalanche Forecast

Issued: Dec 19th, 2018 3:01PM

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

michael.olsthoorn, Alberta Parks

Kananaskis.

More snow and more wind have created windslabs in the alpine. Approach larger slopes with caution. We are approaching the upper end of Considerable for avalanche hazard.

Summary

Confidence

Moderate - Due to the number and quality of field observations

Weather Forecast

Another 10cm of snow has fallen since Wednesday which brings our storm snow up to about 50cm. Thursday night is forecast to bring another 5-10cm of snow. Friday is to bring light flurries with alpine winds of 30km/hr SW winds with gusts up to 50km/hr. Temperatures for Friday in the alpine will be around -12c. If Friday brings more snow than forecasted, the avalanche hazard could easily tip towards a HIGH hazard. The outlook for the weekend is for a drier airmass with cooler temperatures.

Avalanche Summary

4 new avalanches were observed on Wednesday Dec.19: -Two size 1.5 and one size 2 avalanches East aspect in the alpine near the Tent Ridge zone.-One size 2 avalanche East aspect in the alpine was observed between Black Prince and Hero's knob-Keep in mind that human triggering is still likely.

Snowpack Summary

Another 10cm of snow that fell Tuesday night brings our storm snow up to 50cm. Lee features are much more loaded (up to 90cm of storm snow). These loaded lee features are a good indication of the recent wind transport; it will be important to look for windslabs before venturing into bigger terrain. Below this storm snow are surface hoar and facet crystals which are creating a weak sliding surface for the snow to be reactive; we are calling this the December facet layer interface and it is producing natural avalanches. There is still concern for this recent storm snow to trigger the October facet layer at the bottom of the snowpack.

Problems

Wind Slabs

There is still concern for human-triggering of wind slabs with the failure plane down 30 to 50cm at Treeline and deeper in the Alpine.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Avoid freshly wind loaded features.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

The basal layers are very weak, even by Rockies standards. Any avalanche triggered in the upper snowpack is likely to step down to the basal layers. Extra caution is required to manage this avalanche problem.

Be cautious in shallow snowpack areas where triggering is more likely.Avoid unsupported slopes.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Dec 20th, 2018 2:00PM