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Archived

Avalanche Forecast

Apr 17th, 2015–Apr 18th, 2015
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: 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.

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

Avalanche 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