Avalanche Forecast

Issued: Apr 15th, 2015 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

Strong sun on new snow will make conditions touchy today, with solar triggered avalanches and cornice failures expected. Below treeline we are beginning to see a melt-freeze cycle, use caution when the crust is breaking down.

Summary

Weather Forecast

Expect mostly dry and clear weather until Friday. Today strong solar with light west winds and an alpine high of -1'C will destabilize the recent storm snow. Thurs will be similar but warmer with freezing levels rising to 2100m, a high 2'C and temps will stay warm overnight. Fri will be increasingly cloudy with showers and freezing levels to 2400m.

Snowpack Summary

Up to 50cm of snow has settled into a slab sitting a crust on solar aspects and surface hoar on sheltered north and east aspects. Wind effected snow at treeline and above. Above 1700m the top 40-50cm is dry with moist or wet snow below it with multiple crusts in the top 1.5m of the snowpack. Sustained warm temps will rapidly weaken the snowpack.

Avalanche Summary

2 size 2 naturals were observed along the highway yesterday, triggered by windloading. On Sunday, skiers triggered slab avalanches to size 1.5 in the Tree Triangle gully at ~2000m, 30-40cm deep, 20m wide and 75m long. In the surrounding region there were reports of cornices triggering slabs, and skier remote's and accidentals to size 2.

Confidence

Timing or intensity of solar radiation is uncertain

Problems

Storm Slabs

40cm of recent snow has settled into a slab sitting on surface hoar on N'ly aspects and a sun crust on S aspects. Strong winds at ridgetop have created deeper pockets and loaded lee slopes. Today's strong sun will likely make it more reactive.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Loose Wet

The new snow will get a strong dose of sun today and loose avalanches are expected. Once moving, avalanches may dig down into wet snow deeper in the snowpack resulting in large wet avalanches.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Cornices

New snow and strong winds at ridgetop have caused the existing cornices to grow even larger. Today they will be weakened by strong solar. Large cornice failures have been observed recently, sometimes triggering very large deep slab avalanches.

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

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

2 - 4

Valid until: Apr 16th, 2015 8:00AM