Avalanche Forecast

Issued: Apr 21st, 2015 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

Temps stayed warm overnight and conditions will deteriorate rapidly today with another very warm and sunny day. Travel early and quickly in exposed areas; large avalanches may reach their run-outs even when temps are still cool in the valley bottom.

Summary

Weather Forecast

One more hot sunny day is forecast. Today will be sunny with a few clouds later in the day. Alpine temps may climb to 15'C with freezing levels to 3000m, and only light SW winds. By Wed expect clouds and isolated showers, freezing levels to 2700m and gusty winds. Thursday will be similar with freezing levels to 2400m.

Snowpack Summary

There was a good overnight refreeze at valley bottom, but at treeline and in the alpine temps stayed above freezing. On solar aspects is moist and composed of multiple crusts, while on sheltered north aspects dry snow can still be found above ~2100m. A 30-60cm slab over a crust on solar aspects and surface hoar on North aspects remains a concern.

Avalanche Summary

Strong solar and warm temps triggered numerous loose and slab avalanches from all aspects other than due North, and elevations ranged from 1800m to 2600m. Most of the wet avalanches were 2.5's but there were a few size 3's, including a size 3 glide crack release on Mt Tupper. Avalanche activity started around 11am and continued into the evening.

Confidence

Problems

Loose Wet

Expect touchy condition due to continued very warm temps and strong solar. There is a strong melt-freeze crust at valley bottom, but above 1900m temps stayed above freezing overnight and the snowpack will destabilize very quickly.

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, South, South West.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Persistent Slabs

Crusts on solar aspects, and surface hoar on shaded slopes, buried down 30-60cm are still a concern. Daytime warming, loose avalanches and skiers can trigger this layer. Natural avalanches continue to observed on these layers.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.Test slopes before committing to them.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 3

Cornices

Large cornices loom over many of the slopes that hold good snow. While those slopes are in the shade, the cornice itself is likely in the sun making them weaker and more likely to fail.

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 - 3

Valid until: Apr 22nd, 2015 8:00AM