Avalanche Forecast

Issued: Apr 27th, 2013 8:00AM

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

danyelle magnan, Parks Canada

Glacier.

Summary

Weather Forecast

A series of fronts over the next few days before another ridge of high pressure builds on Tues. Today will be overcast with 5mm of precip and freezing levels at 2000m. Sunday will see a few sunny breaks before the next system arrives on overnight. Up to 20mm of precip overnight into Monday, with freezing levels falling to 1300m and strong W winds.

Snowpack Summary

8mm of rain turned to snow early this am above 1900m, but freezing levels are expected to rise to 2000m 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

9 size 2-2.5 loose, moist natural avalanches were observed along the highway yesterday. They were from all aspects, start zones were 2000-2700m, and were triggered by warm temps. This activity will continue today due to rain on snow. Cornice failures remain a concern for triggering slab avalanches, mostly failing on PWL's in the top meter.

Confidence

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

Problems

Loose Wet

Rain to ridgetop, briefly turned to snow above 1900m overnight, but freezing levels are expected to be 2000m today. Loose wet avalanches are possible from all elevations and aspects.

Watch for terrain traps where small amounts of snow will acumulate into deep deposits.Avoid avalanche terrain during periods of rain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

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. Large cornices have formed and may fail due to warm temps and rain.

Be cautious as you transition into wind affected terrain.Give cornices a wide berth when travelling on or below ridges.

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 have been triggered by skiers/riders in the past few weeks. They may also be triggered by other avalanches stepping down, or due to cornice fall.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

2 - 3

Valid until: Apr 28th, 2013 8:00AM