Avalanche Forecast

Issued: Mar 16th, 2015 3:00PM

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

jeremy.mackenzie, Alberta Parks

Kananaskis.

Storm snow totals of up to 50cm have formed slabs in the alpine and upper treeline terrain. The warm sun of mid-March will be a major factor in increasing the hazard on solar aspects during any sunny period. Plan your approach to terrain accordingly.

Summary

Confidence

Good

Weather Forecast

A mix of sun and cloud expected on Tuesday with freezing levels near 2100m. Alpine temperatures should reach -1 celsius and winds will be light from the South. Wednesday should be a bit cloudier with a trace of precipitation.

Avalanche Summary

Several naturally triggered loose avalanches (both dry and wet) occurred on all aspects in steep terrain at alpine and treeline elevations up to size 1.5. In addition, ski cutting produces sluffs up to size 1.5 on steep north facing terrain. A few slab avalanches also occurred in the past 24hrs. These are all naturally triggered slabs (some by solar triggering) and occurred in alpine terrain on all aspects up to size 2.0.

Snowpack Summary

The snowpack is highly variable depending on aspect and elevation. Up to 50cm of storm snow has fallen at treeline. On polar aspects moderate shears exist at the storm snow interface (down 50cm) and easy to moderate shears exist within the storm snow down 15 to 30cm. Thin storm slabs formed early in the storm, but then the winds backed off. This has left hidden slabs buried under low density snow at treeline. In the alpine slabs are prominent and a few avalanches have occurred related to this problem (see Avalanche Activity Discussion). On solar aspects a completely different situation exists. On these aspects the storm snow has already settled to 30cm and seems well bonded to the underlying crusts below 2400m. Above this elevation the storm snow seems to have bonded less well and numerous point release avalanches have been observed in steep alpine terrain. The surface snow on solar aspects was moist by midday. On all aspects below 2100m the storm snow sits on a very dense and strong rain crust (about 1cm thick) that was formed on Saturday. This rain crust is supportive to skier traffic.

Problems

Storm Slabs

Storm slabs are well developed in the alpine. However, at treeline slabs were formed early in the storm and then the wind backed off which has left hidden slabs. Snowpack tests today gave moderate results at the storm snow interface down 50cm.

Avoid lee and cross-loaded terrain near ridge crests.>Avoid freshly wind loaded features.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 4

Loose Wet

The mid-March sun packs a lot of energy. Solar aspects will see avalanche activity increase through the day with daytime heating and solar radiation.

Avoid travelling under cliffs that are exposed to sluffing from above.>Be cautious of sluffing in steep terrain.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

Recent loading may make the basal weaknesses more sensitive, especially in shallow snowpack features.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 5

Valid until: Mar 17th, 2015 2:00PM