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Avalanche Forecast

Dec 19th, 2016–Dec 20th, 2016
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
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
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Purcells.

More snow, strong winds and warmer temperatures are driving the danger ratings. It's a good time to make conservative choices and stick to simple terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Tuesday

Weather Forecast

The Interior is under a strong zonal flow that is responsible for pushing out the cold air and bringing in the snow! We can expect to see an additional two - three systems move across the region through the forecast period.Tuesday: Snow 8-15 cm with freezing levels rising to 1000 m. Alpine temperatures -9 and ridgetop winds 35-60 km/hr.Wednesday: Snow 5 cm with freezing levels dropping to valley bottom. Alpine temperatures -11 and ridgetop winds 30-55 km/hr.Thursday: Snow 5-10 cm with alpine temperatures -9. Ridgetop winds 15-35 km/h.

Avalanche Summary

Loose snow and wind slab avalanches up to size 2 were reported on Monday. Given the weather forecast we can expect to see avalanche activity on Tuesday.

Snowpack Summary

Up to 15 cm of storm snow sits over a plethora of old snow surfaces including stiff wind affected snow, faceted (sugary) crystals and surface hoar crystals that formed in locations sheltered from the wind. The new snow will likely have a poor bond to these surfaces. 20-40 cm below this new snow sits an older buried surface hoar layer, reported from the Dogtooth Range. This layer may me reactive with additional load. The mid-November crust is buried down around 70-90 cm and test results have been variable from sudden failures to no results. In shallower snowpack areas reports indicate that the bond to the crust is weakening. Tracking and monitoring this potentially weak interface is crucial especially as we move forward into this snowy period where the snowpack will see more load.

Avalanche Problems

Storm Slabs

New snow and strong winds will continue to build fresh storm slabs. They are reactive due to the poor bond with the old snow surfaces.
Avoid avalanche terrain during periods of heavy loading from new snow and wind.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 3

Loose Dry

Loose dry avalanches/ sluffing are likely from steeper slopes and terrain features.
Use caution above cliffs where small avalanches may have severe consequences.Watch for terrain traps where your sluff will accumulate into deep deposits.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 2