Avalanche Forecast

Issued: Mar 22nd, 2013 8:00AM

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

catherine brown, Parks Canada

Glacier.

Condtions have improved greatly in a week. Good group management and appropriate terrain selection is still critical, as always.

Summary

Weather Forecast

Light, convective snow is forecast for the park today, also with strong solar inputs likely. Alpine temps will rise to -5. Strong temperature fluctuations are expected between day and nighttime temperatures over the next three days. Over this period the skies will continue to clear as a high pressure system moves over the region.

Snowpack Summary

30cm of storm snow is dry down to 1400m, with sun crust on solar aspects. Strong southerly winds deposited this snow on lee aspects at treeline and the alpine. The storm snow is reactive to rider triggering in steep and unsupported terrain, especially at treeline. The March 11 surface hoar-suncrust weak layer is down about a meter.

Avalanche Summary

No new natural avalanches were observed along the highway corridor yesterday in the park. A small avalanche cycle occurred on Wednesday night, mostly from steep start zones on Mt. MacDonald. Also on Wednesday, explosive testing produced a size 1 avalanche on a north aspect at treeline.

Confidence

Due to the number of field observations

Problems

Storm Slabs

New snow is reactive to rider triggering. Use caution in steep terrain and unsupported features. Avalanches with large consequences may run on solar aspects. A sun crust is present down 30 cm. Northerly aspects with wind loaded snow may be touchy.

Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 3

Wind Slabs

Isolated wind slabs in the alpine and near ridge crests have surprised a few skiers. These failures could break down to deeper instabilities. Cornices are very large and unsupported.

Be careful with wind loaded pockets Use caution in lee areas in the alpine. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Persistent Slabs

Two weak layers are buried down 1-1.5m. Though unlikely, a large trigger like a cornice or another avalanche may cause these weak layers to fail.

Conditions are greatly improved, but be mindful that deep instabilities are still present.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Mar 23rd, 2013 8:00AM