Avalanche Forecast

Issued: Mar 19th, 2015 9:40AM

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

rbuhler, Avalanche Canada

South Rockies.

Wind slabs may be building at higher elevations where there is still dry snow. Continued warm conditions means loose wet avalanches remain a concern during the heat of the afternoon.

Summary

Confidence

Fair

Weather Forecast

A mix of sun and cloud is expected for Friday with freezing levels reaching around 2500m and moderate-strong SW winds in the alpine. The north end of the region could see light scattered precipitation on Friday. On Saturday, light precipitation is expected and models are currently showing 2-6mm. Freezing levels are forecast to fall to below 1500m by Saturday afternoon. Alpine winds should remain moderate-strong from the SW. A mix of sun and cloud is expected for Sunday with freezing levels around 2000m.

Avalanche Summary

A widespread natural avalanche cycle to size 2.5 occurred on Monday during the storm. These were primarily storm slab avalanches but several stepped down to deeper persistent weak layers or to the ground in steep unskiable terrain. At lower elevations, loose wet avalanches up to size 2.5 were reported as well as isolated wet slabs. On Friday, wind loaded areas are the biggest concern. New wind slabs will be touchy and may overload older wind slabs in leeward terrain features. Loose wet avalanches are a concern on sun-exposed slopes during the heat of the afternoon or areas that receive rain.

Snowpack Summary

The recent storm snow is settling into a cohesive slab which is typically 30-40cm thick. This snow is now moist or wet on all aspects and elevations except high elevation north facing terrain. Wind affected snow is expected in the high alpine and ongoing winds may be adding additional load to slabs in leeward terrain features. Up to at least treeline elevation, the snowpack below the new storm snow is moist or wet from the warming and heavy rain last week. A weak rain crust sits between the storm snow and the lower snowpack. The thick mid-February crust has broken down and is no longer supportive. There are a couple older persistent weak layers in the midpack that are probably breaking down but will remain an isolated concern while the snowpack remains warm.

Problems

Wind Slabs

Strong winds are forming thin new wind slabs or adding to the old slabs in leeward terrain features.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Loose Wet

Solar radiation and daytime warming will weaken the upper snowpack and increase the likelihood of loose wet avalanches. Overhead hazards like cornices could also fail and trigger slab avalanches from the slopes below.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Deep Persistent Slabs

A crust/facet layer down 90-150cm still has the potential to produce very large avalanches with a heavy trigger like a cornice failure or a smaller avalanche in motion stepping down.

Be aware of thin areas that may propogate to deeper instabilites.>Caution around convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Mar 20th, 2015 2:00PM