Archived

Avalanche Forecast

Apr 21st, 2015–Apr 22nd, 2015

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

4: High

The avalanche danger rating at treeline will be high

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: 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.

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

Avalanche 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