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Avalanche Canada triley, Avalanche Canada

South Rockies Avalanche Forecast

Mar 16th, 2016 10:13AM

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

Sun and warm temperatures are expected to increase the avalanche danger.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Some cloud overnight with a chance of convective flurries, and freezing levels dropping to valley bottoms. Mix of sun and cloud on Thursday with moderate northeast winds and 2-3 cm of new snow. Clear on Friday with strong solar radiation, light winds and daytime freezing levels up to 1700 metres. Clear on Saturday with moderate southwest winds and freezing levels rising up to at least 2200 metres.

Avalanche Summary

In the Crowsnest north area, previous natural cornice falls had not released any slab avalanches on the slopes below. 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

On Wednesday the field team was in the Crowsnest north area around Window Mtn, where they found 155 cm of snow on the ground at 2250 metres on a north aspect. The foot penetration was 35 cm, but the light winds were not transporting this available snow today. Ski penetration was about 15cm. In Smith Basin on Tuesday, our field team found a thinner snowpack with only 140-200 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 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
Recent wind slabs may continue to be triggered by light additional loads like individual skiers or riders.
Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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 fragile, and may fall off naturally during periods of strong solar radiation.
Give cornices a wide berth when travelling on or below ridges.>Pay attention to overhead hazards like cornices.>

Aspects:

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

Elevations:

Alpine, Treeline.

Loose Wet

An icon showing Loose Wet

Likelihood

Likely - Possible

Expected Size

1 - 2
Forecast strong solar radiation and warm daytime temperatures may result in loose wet or moist snow releasing from steep terrain.
Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects:

North, North East, East, South East.

Elevations:

Alpine, Treeline.

Valid until: Mar 17th, 2016 2:00PM