Avalanche Forecast

Issued: Apr 26th, 2013 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

Above freezing temps at all elevations prevented an overnight freeze.

Summary

Weather Forecast

The ridge of high pressure is breaking down today. Temps will remain above freezing well into the alpine with frequent sunny breaks. Winds will increase to strong W'ly. On Sat, a cold front will clouds and up to 10mm of precip with freezing levels around 2000m. On Sunday, precip will taper off and temps and freezing levels will start to lower.

Snowpack Summary

No overnight freeze with warm temps. What did tighten will lose strength will lose strength rapidly today. Surface wet grains overly a near isothermal snowpack with various crusts/PWL in top meter. In the alpine, a mix of hard and soft slab persists, with dry snow on polar aspects above 1900m. Lots of variability in snow depth across terrain.

Avalanche Summary

There have been no new natural avalanche observations in the past 3 days, in part due to fewer people in the backcountry to report. Cornice failures remain the biggest concern for triggering larger slab avalanches, which are mostly failing on the April 3 crust-surface hoar, down 40-80cm. Cloud today will reduce the likelihood of moist avalanches.

Confidence

Problems

Wind Slabs

Sustained strong S'ly winds at higher elevations is creating wind slabs and adding to the variability of snow depth across terrain. Some areas will be loaded and others thin. These slabs have a potential for wide propagations in the right terrain.

Watch for areas of hard wind slab in steep alpine features.Be careful with wind loaded pockets

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

2 - 3

Persistent Slabs

Large avalanches failing on deeper weak layers are still being triggered by skiers/riders. They are also sporadically occurring naturally, triggered by wind loading, cornice fall and solar warming.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Loose Wet

Temps stayed above freezing at all elevations preventing an overnight freeze. Loose wet avalanches are most likely below treeline, especially during sunny breaks. They are possible at higher elevations due to high freezing levels.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.

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

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 27th, 2013 8:00AM