Archived

Avalanche Forecast

Dec 21st, 2016–Dec 22nd, 2016

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

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

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: North Columbia.

Mostly a wind slab problem, but as the upper snowpack settles, things might start to change. If you see signs of instability, like whumpfs (rapid settlements), or see small rolls peel off, avoid unsupported (convex) terrain features.

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Thursday: 5-10 cm new snow is expected. Ridgetop winds southwesterly 50-60 km/h in the morning, becoming 30-40 km/h by the afternoon. Treeline temperatures around -4C. Friday: Light snow in isolated areas, no significant accumulation expected. Winds becoming calm. Treeline temperatures around -7C. Saturday: Dry and sunny. Light northeasterly winds. Treeline temperatures around -13C.

Avalanche Summary

On Tuesday, a skier triggered a small wind slab avalanches at 1900 m. There were a few reports of small natural wind slabs above 2000 m on easterly aspects and explosive controlled avalanches were noted in similar terrain up to size 2.5. On Monday numerous natural slab avalanches were reported up to size 2.5 on a variety of aspects and elevations.

Snowpack Summary

Up to 60 cm of recent storm snow sits on 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. Snowpack tests indicate easy, sudden shears on this interface, indicating a poor bond with the underlying snow. However, so far, avalanches associated with this layer have been relatively small (size 1 to 2) and mostly limited to windy areas or unsupported features. This may change as the upper snowpack starts to become stiffer and denser - if it does we may start to see wider propagation resulting in the potential for larger avalanches. Telltale signs of this will be whumpfs or remote-triggering of avalanches from flat terrain. Deeper in the snowpack exist two layers that could still be important in isolated areas. The first is a spotty surface hoar layer that sits 40-100 cm down, the second is the mid-November crust now buried 100-200 cm deep.

Avalanche Problems

Wind Slabs

Heavy storm snow amounts and strong southwest winds have built fresh and reactive storm slabs that sit over a variety of weak sliding layers. Rider triggering is likely.

Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.Avoid all avalanche terrain during periods of heavy loading from new snow and wind.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3