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Archived

Avalanche Forecast

Mar 20th, 2017–Mar 21st, 2017
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Glacier.

The last weeks storm cycle has drastically changed the snowpack adding a significant new load.  Strong solar warming today will make the new storm slab more reactive.

Weather Forecast

Today we can expect a break from the stormy weather with a sunny day and building cloud in the afternoon.  In the alpine the daily high will get up to -7*C, with freezing level to 1300m & winds from the east at 15kph. Tuesday will be more unsettled as a low moves across southern BC bringing light snowfall and 1900m freezing levels to Roger's Pass.

Snowpack Summary

Saturday's storm was the last in a series that brought heavy rain/snow, extreme winds (100+ km/h) and very warm temps. Widespread wind and storm slabs have formed at tree-line and alpine elevations as a result. Below approx. 1700m a rain crust is prevalent. This crust caps a moist upper snowpack.

Avalanche Summary

Natural and artillery controlled avalanches to size 4 were observed on Saturday. The biggest avalanche was Macdonald West Shoulder failing simultaneously in 4 start zones naturally, ripping out mature timber and running to the valley floor. Large fracture lines are visible in the backcountry showing wide propagation and multiple step down layers.

Confidence

Timing or intensity of solar radiation is uncertain

Avalanche Problems

Storm Slabs

Heavy snowfall and extreme SW winds formed reactive storm slabs at tree-line and alpine elevations. These overlie various weak interfaces in the upper snowpack and need time to readjust to the new load. Strong solar warming today will test this slab.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 2 - 4

Persistent Slabs

Persistent deep layers made a triumphant return during our most recent avalanche cycle and they remain a cause for concern. As surface slabs fail, avalanches can easily step down to weak layers from late February, or deeper in shallow areas.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for whumpfing, hollow sounds, and shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 4

Cornices

Abundant warm snow with constant SW winds has built up some very large cornices along ridge-tops. These beasts are fragile, HUGE triggers with the potential to start large avalanches. They will become even more fragile with solar warming today.
Minimize exposure to overhead hazard from cornices.Pay attention to overhead hazards like cornices which could easily trigger deep slabs.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 2 - 4