Avalanche Forecast

Issued: Dec 20th, 2018 3:00PM

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

matt.mueller, Alberta Parks

Kananaskis.

We do not have a trustworthy snowpack at the moment. Steep treeline features (I.E. Tryste Chutes) are especially suspect. Runs that are normally "good to go", should be treated with caution and respect.

Summary

Confidence

High.

Weather Forecast

Snow tapering off tonight. Totals could be as much as 10cm. Alpine winds will remain moderate to strong from the west with temperatures falling to -12°c by tomorrow afternoon. Long term, we are expecting only flurries with mostly cloudy skies. Another pulse is possible by early next week.

Avalanche Summary

It turns out the cycle reported yesterday was more widespread than we originally thought. We saw many size 2 avalanches today at treeline with impressive propagations. Large alpine paths have also run. It appears that any aspect from North to South is suspect lately. In all cases, the Dec 10th facets are to blame. Be extremely cautious with any slope that hasn't slid.

Snowpack Summary

More snow arrived last night and today. We now have 40-70cm on top of the Dec 10th facet layer at treeline. Winds have continued to howl from the west today. The alpine is either wind scoured, or windslabs. Treeline also has these wind slabs, however they not as dense, which makes them tougher to predict in terms of "triggerability". A profile today at 2000m had the Dec 10th down about 40cm. There were repeatable test results (compression test 19, sudden collapse) on this layer indicating it is a serious concern. The bottom line? We have several very weak layers lingering in the lower snowpack with a windslab sitting on top. Basically a house of cards waiting to reach the tipping point.

Problems

Persistent Slabs

The widespread cycle we experienced yesterday tells us these slabs are primed to go. Even areas with a soft slab may react due to the weak nature of the Dec 10 facets. The layer is thick, so expect wide propagation despite softer than normal slabs.

Avoid freshly wind loaded features.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Avoid areas with overhead hazard.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

There are a number of crusts at, or near the bottom of the snowpack. This collection of crusts and facets (weak snow) is not trustworthy. Large triggers, or poor terrain choices could easily disturb these deep layers, causing a large avalanche.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Dec 21st, 2018 2:00PM