Avalanche Forecast

Issued: Mar 23rd, 2013 8:00AM

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

catherine brown, Parks Canada

Glacier.

Loose avalanches triggered by solar warming is the main concern today. If the sun remains strong in the afternoon, watch for a moist surface indicating the snowpack is heating up. Limit exposure to hot spots above you like rocks and trees.

Summary

Weather Forecast

Clear to scattered skies are forecast for the park today. Temperatures will rise, expect alpine temps around -4 and a 1200 m freezing level. Winds over the next three day period are forecast to be light with no precipitation, strong diurnal temperature fluctuations and lots of solar input during the day.

Snowpack Summary

25cm 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 may be 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

A couple loose avalanches up to size 2 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

Timing or intensity of solar radiation is uncertain

Problems

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.

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

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.Cornices become weak with daytime heating, so travel early on exposed slopes.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

3 - 4

Valid until: Mar 24th, 2013 8:00AM