Avalanche Forecast

Issued: Mar 25th, 2016 8:05AM

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

danyelle magnan, Parks Canada

Glacier.

We are coming into a busy weekend, with tricky avalanche conditions. There is great skiing to be had, but keep your guard up. Remember that other groups may be above or below you & regroup in safe spots. Avoid slopes with large cornices looming above

Summary

Weather Forecast

A weak ridge of high pressure is developing today. Unsettled weather is expected through the weekend. Throughout the weekend expect flurries & a mix of sun and cloud, which may have a strong "greenhouse effect". Alpine temps are expected to be -3'C with moderate W'ly winds continuing to load lees. A spring melt-freeze cycle should start to develop.

Snowpack Summary

~50cm of new snow in the past 5 days, combined with mild temps and sustained SW winds, is building a deep storm slab. This slab overlies a crust, which provides a good sliding surface, on all aspects up to ~2200m and to ridgetop on solar aspects. Multiple crusts in the upper meter may promote step-down avalanches.

Avalanche Summary

Yesterday, avalanches up to size 2.5 were triggered by skiers. They were generally larger on N'ly aspects where the slab is deeper due to wind-loading. They were easily triggered in predictable places; steep slopes with a convexity. Natural size 2-3 avalanches were observed from all aspects along the highway. Several were from skiable terrain.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Storm Slabs

Daily doses of 10-15cm is building a deep storm slab. Combined with sustained SW winds, slabs will be deeper on lee and cross-loaded features. Yesterday storm slabs were easy to trigger on convexities and wind loaded features. Expect the same today.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

2 - 3

Persistent Slabs

A series of crusts on solar aspects, buried up to 1.2 m deep, remain a concern. Tests generally take a hard force but continue to produce sudden planar results. This suggests that smaller avalanches, or cornice failures, may trigger large avalanches.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

There has not been an overnight freeze below tree-line for several days. Expect avalanches to be easy to trigger on steep slopes where moist snow overlies a crust. While unlikely to be large, avalanches will gain mass in gulleys and terrain traps.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Mar 26th, 2016 8:00AM