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Avalanche Canada triley, Avalanche Canada

South Rockies Avalanche Forecast

Mar 15th, 2016 9:28AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Cornices.

Wind slabs and cornice falls continue to be a concern. Watch for pockets of wind slab in the entrances to chutes and gullies. Avoid slopes below cornices, especially if the sun comes out.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Some chance of convective flurries overnight with moderate west or northwest winds and freezing levels down to valley bottoms. A mix of sun and cloud on Wednesday with some lingering flurries, moderate westerly winds and daytime freezing levels climbing up to 1500 metres. Mix of sun and cloud on Thursday with light northeast winds, 3-5 cm of new snow, and a good overnight freeze; daytime freezing levels up to 1300 metres. Clear on Friday with a good overnight freeze, light winds and daytime freezing levels climbing up to 1700 metres

Avalanche Summary

No new avalanches reported. Cornices were reported to be smaller in the Smith basin area. On Monday our field team in the Crown Mtn area observed a natural cornice fall size 2.0 that did not release a slab on the steep slope below. The field team also observed the debris from a previous cornice fall that probably released over the weekend. On Saturday a few natural cornice failures to size 2 were observed in extreme terrain. On Friday a few different very large avalanches (to size 3.5) were observed that failed naturally on southerly facing alpine features. These avalanches were likely triggered by falling chunks of cornice impacting thin snowpack areas in the far north of the region. Debris ran down the track well into the below treeline vegetation band.

Snowpack Summary

In Smith Basin on Tuesday, our field team found a thinner snowpack with only 145 cm on the ground. They found about 10 cm of recent storm snow above a 2 cm breakable crust that was not supportive. The March 7th crust in Smith basin was down about 20 cm, with decomposing snow below that becoming facetted weak crystals deeper in the shallow weak snowpack. There were no notable test results, and evidence of aggressive slope testing on east-south-west aspects that did not trigger any releases. On Monday at 1920 metres in the Crown Mtn area there was 17 cm of new snow above a breakable 2 cm crust. Below the crust there was dry snow at this elevation. We estimate the the crust extends up to about 2000 metres. Strong southwest winds have created widespread wind slabs at treeline and above.

Problems

Wind Slabs

An icon showing Wind Slabs

Likelihood

Possible

Expected Size

1 - 3
Wind slabs are expected to continue to linger in the lee of terrain features that have been exposed to southwest winds over the past few days.
Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

Aspects:

North, North East, East, South East, South.

Elevations:

Alpine, Treeline.

Cornices

An icon showing Cornices

Likelihood

Possible

Expected Size

2 - 4
Cornices are large and may be fragile due to new growth. Daytime warming and strong solar radiation may increase the likelihood of natural cornice falls.
Pay attention to overhead hazards like cornices.>Give cornices a wide berth when travelling on or below ridges.>

Aspects:

North, North East, East, South East, South.

Elevations:

Alpine, Treeline.

Valid until: Mar 16th, 2016 2:00PM