Avalanche Forecast

Issued: Mar 6th, 2017 6:12PM

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

mgrist, Avalanche Canada

South Rockies.

A week of snowfall and strong winds has left wind slabs and some cornices primed for human triggering. Avoid overhead hazards and evaluate terrain carefully before committing to bigger lines.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

We're looking at occasional (intense) flurries and cool temperatures throughout the forecast period. TUESDAY: Flurries with up to 5cm of new snow, 20-40 km/h southeast winds, alpine temperatures around -11 C. WEDNESDAY: Flurries with 5-10 cm of new snow, 20-30 km/h east winds, alpine temperatures around -12 C. THURSDAY: Cloudy with scattered flurries and up to 3-5 cm of new snow, 30-50 km/h east winds, alpine temperatures around -14 C.

Avalanche Summary

On Saturday, several size 2 natural storm slabs were reported in alpine terrain and explosive control and ski cutting produced size 1-1.5 avalanches at treeline and in the alpine.Natural activity is expected to taper off, but storm and wind slabs will remain susceptible to human triggering.

Snowpack Summary

We've had another 15-25 cm of snow since Saturday, bringing the total from the past week to 50-80 cm. Strong southwesterly winds redistributed the new snow onto leeward slopes, building thicker and stiffer slabs. The new snow will likely have a poor bond to the old snow interface that consists of stiff wind slabs, crusts, and facets. The mid-pack in this region is generally strong, but the bottom third of the snowpack is composed of weak facets (sugary snow crystals). Approximately 100-120 cm of settled snow sits above this weak layer of sugary, rotten facets that developed in December. This remains a concern and should be on your radar, especially with the recent loading from snow and wind.

Problems

Wind Slabs

Gusty southwest winds at upper elevations have formed fresh wind slabs on leeward slopes and behind terrain features.

Use caution above cliffs where small avalanches may have severe consequences.Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

A weak layer near the base of the snowpack has the potential for large avalanches, especially in areas with minimal rider compaction or thin variable snow cover.

Pay attention to overhead hazards like cornices which could easily trigger the deep persistent slab.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Mar 7th, 2017 2:00PM