Avalanche Forecast

Issued: Mar 18th, 2015 9:42AM

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

rbuhler, Avalanche Canada

South Rockies.

Lingering storm slabs remain a concern, especially in the alpine. Avoid steep unsupported slopes and convexities. Use extra caution on sun-exposed slopes during the heat of the afternoon.

Summary

Confidence

Fair

Weather Forecast

Thursday should be a mix of sun and cloud. Freezing levels are forecast to peak around 2000m and alpine winds are expected to increase to strong from the SW to W. Friday should be similar with a mix of cloud and sun, and moderate to strong alpine winds from the SW. Freezing levels are expected to climb as high 2500m on Friday afternoon. Light precipitation is possible on Saturday and freezing levels are forecast to drop back to 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. Natural activity quickly tapered off following the storm but the storm slab is expected to still be reactive to human-triggering. It is best to avoid steep unsupported slopes and convexities, as well as steep gully features. There is also concern for avalanches to step down to deeper persistent weak layers in isolated areas. Loose wet avalanches are a concern on sun-exposed slopes during the heat of the afternoon.

Snowpack Summary

The recent storm snow is settling into a cohesive slab which is typically 30-40cm thick. Up to at least 2000m 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

Storm Slabs

30-40cm thick storm slabs sit over a new rain crust. At lower elevations or on sunny slopes these slabs may be moist or wet. The slabs are expected to be most reactive at higher elevations, especially on steep, unsupported terrain features.

Avoid steep unsupported slopes.>Be alert to conditions that change with elevation.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Loose Wet

Solar radiation and daytime warming will likely deteriorate the upper snowpack, initiating 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: All elevations.

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 6

Valid until: Mar 19th, 2015 2:00PM