Avalanche Forecast

Issued: Apr 17th, 2015 8:00AM

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

andrew jones, Parks Canada

Glacier.

Warm overnight temperatures prevented a refreeze of the upper snowpack. Stay clear of slopes receiving direct solar input and remember that cornices over shaded slopes are getting baked from behind. Large avalanches are likely today.

Summary

Weather Forecast

Warm daytime temperatures continue with freezing levels climbing to 2500m and an alpine high of 6. Ridge winds are SW 25km/h gusting to 70km/h. Mostly sunny today but trace amounts of rain are expected from convective precipitation. Alpine temperatures will remain warm tonight with a temperature inversion. Strong sun and warmth this weekend.

Snowpack Summary

Warm temps yesterday weakened the upper snowpack. High overnight temperatures prevented a refreeze of the surface snow. A reactive slab on a persistent weak layer down 50cm sits on a crust on solar aspects and surface hoar on sheltered NE aspects. A moist or wet layer that persists down 50cm will weaken rapidly with the forecasted warm temps.

Avalanche Summary

Several natural size 1.5 solar triggered avalanches were observed in the Balu Pass area. Avalanches started as loose snow and triggered slabs on unsupported features. A size 2.0 natural avalanche was observed on the W side of Mt Cheops, into Cougar Valley. Avalanches cycles are expected during peak warming periods of the day.

Confidence

Problems

Persistent Slabs

A slab sits on a persistent weak layer buried 40-60cm or deeper where strong winds have deposited snow in lee areas. The layer is surface hoar on NE aspects and a sun crust on S aspects. Sun, loose avalanches and skiers can trigger this layer.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Loose Wet

Warm overnight temperatures set the stage for loose wet avalanches. When the strong spring sun hits the slopes, expect to see surface snow on the move. Loose slides can dig down to wet snow deeper in the snowpack resulting in larger 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

Expected Size

2 - 3

Valid until: Apr 18th, 2015 8:00AM