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Avalanche Forecast

Archived

Dec 1st, 2014–Dec 2nd, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Purcells.

Snowpack structure varies greatly across the region. Pay close attention to localized conditions and choose conservative terrain.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Very light flurries and a mix of sun and cloud are expected for the forecast period as a ridge of pressure remains parked over the province. Alpine winds will be moderate to strong from the northwest on Tuesday. On Wednesday and Thursday the winds should be generally light from the southwest. Alpine temperatures should hover at about -12 on Tuesday, rising slightly for Wednesday and Thursday. No significant snowfall is expected until Friday.

Avalanche Summary

Widespread natural activity up to size 3 was reported on Friday around Golden. Remote triggering from up to 50m away was also reported. Slabs were up to 1m deep and avalanches were running full path. On Saturday, avalanche control produce numerous more avalanches up to size 3. Check out skiinggolden.com for an impressive video of avalanche control on Saturday.Widespread natural activity up to size 3 was reported on Sunday in the Invermere area. This occurred between Thursday and Saturday. Explosives and ski cuts on Sunday produced several size 1 avalanches in previously controlled terrain.

Snowpack Summary

Last week's storm produced slabs up to 1m thick in the north of the region and around 60cm thick in the south. This slab sits on the mid-November weak layer (surface hoar, facets, and/or a crust). Below this you will likely find a 15-20cm thick layer of sugary facets, which is sitting on a solid rain crust from early November. Reports of whumphing and remote triggering on these layers suggests a persistent weakness with the potential for large propagation and large avalanches. Recent strong and variable winds have likely created dense wind slabs in exposed terrain and resulted in variable snow distribution in the alpine. On Thursday, high elevation rain produced a new crust. In the Golden area this rain crust exists up to around 1600m whereas in the south it is up to 2000m or higher. As temperatures dropped, 10-20cm of new snow fell on top of this new crust.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.