Avalanche Forecast

Issued: Apr 18th, 2014 8:07AM

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

danyelle magnan, Parks Canada

Glacier.

Conditions can change quickly this time of year; rain or sun will rapidly increase danger. Minimize your exposure to steep avalanche paths being loaded by westerly winds, and slopes threatened by cornices and glide cracks.

Summary

Weather Forecast

Today should be mainly cloudy with flurries, with alpine temps of 0 and moderate to strong west winds. Possible sunny periods this afternoon may further destabilize the snowpack. On Saturday, freezing levels are forecast to rise to 2300m with increasing cloud and wet flurries. On Sunday expect scattered flurries, sunny breaks and strong west winds.

Snowpack Summary

A mix of rain and snow fell to 1900m, with temps dropping just to zero, giving no overnight freeze. 10cm of moist HN at treeline (deeper in lee alpine features) is bonding poorly to a crust below. The snowpack on solar aspects is warming to near isothermal levels. There are a series of crusts in the top meter, and the Feb 10 SH is down 1.25m.

Avalanche Summary

Avalanche activity began mid day yesterday. Backcountry skiers reported hearing and observing numerous natural avalanches up the Connaught drainage. Cheops N3 and N4 (STS) were size 2.5, with debris 1.5m deep at valley bottom. Along the highway, size 2.5 loose moist avalanches ran onto the fans of steep paths and one glide crack released a size 2.

Confidence

Timing, track, or intensity of incoming weather system is uncertain

Problems

Wind Slabs

Up to 20cm of moist snow is forming loaded pockets of windslab on lee features. These may bond poorly to the surface below, particularly if they overlie a crust. Forecast winds will continue to load these slopes; natural avalanches are possible.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Use caution in lee areas. Recent wind loading have created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Loose Wet

Moist new snow, mixed with rain, will bond poorly to the weak crust and nearly isothermal snow below. Watch for the possibility of rain showers or sunny breaks, which will weaken the snowpack. Windloading may trigger avalanches, becoming loose wet.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Persistent weak layers deep in the snowpack are tough to trigger but another avalanche or a big cornice failure would wake them up. Rapid warming or rain could also trigger a very large avalanche.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.Pay attention to overhead hazards like cornices.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Valid until: Apr 19th, 2014 8:00AM