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Avalanche Forecast

Dec 12th, 2015–Dec 13th, 2015
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
Below Threshold
The avalanche danger rating below treeline will be below threshold
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
Below Threshold
The avalanche danger rating below treeline will be below threshold
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold

Regions: South Coast.

The Avalanche Danger is expected to peak on Saturday night. If heavy snowfall and/or strong winds persist into Sunday, you should consider the Avalanche Danger to be HIGH.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Sunday

Weather Forecast

An unstable pacific air mass will continue to bring snowfall to the region. On Sunday, expect up to 20cm of snow with extreme southwest winds easing to moderate throughout the day. On Monday and Tuesday, a benign northwesterly flow will bring a mix of sun and cloud, and moderate northwesterly ridgetop winds. Freezing levels should hover around 800m for the forecast period.

Avalanche Summary

I expect a healthy round of storm slab activity in response to new snow and wind forecast for Saturday and Sunday. The timing of the natural avalanche activity is tough to pin-down, although weather models suggest touchiest conditions will develop around midnight on Saturday. Even though the storm is expected to taper-off on Sunday, I would have serious concerns for ongoing human triggering of new storm slabs, especially in higher-elevation, wind-exposed terrain.

Snowpack Summary

By Sunday morning I would expect up to 40cm of new snow to have fallen. Strong southwest winds will have redistributed the new snow into much deeper and potentially reactive storm slabs in lee terrain. These new accumulations will add to the 150cm of recent storm snow that has fallen in the high alpine over the last week. A hard rain crust can be found in the upper snowpack up to the 2200m elevation. Recent tests suggest an improving bond at this interface; however, I'd dig and test this layer before committing to any steeper lines.

Avalanche Problems

Storm Slabs

Heavy snowfall and extreme ridgetop winds on Saturday and Sunday may create potent new storm slabs. The best (and safest) riding will be in sheltered low-angle terrain.
Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Choose conservative lines and watch for clues of instability.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3