Avalanche Forecast

Issued: Feb 26th, 2021 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada kdevine, Avalanche Canada

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The snowpack in the Cariboos is complex. Stick to simple terrain and resist the urge to venture into bigger terrain, now is not the time to get after it!

Summary

Confidence

Moderate - Uncertainty is due to the complexity of the snowpack’s structure. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

FRIDAY NIGHT - Cloudy with clear periods / light to moderate northwest wind / alpine low temperature near -14 

SATURDAY - A mix of sun and cloud / light to moderate northwest wind / alpine high temperature near -13

SUNDAY - Mainly cloudy with a few flurries / strong southwest wind / alpine high temperature near -6 / freezing level 1500 m

MONDAY - Flurries, 5-10 cm / strong southwest wind / alpine high temperature near -7 / freezing level 1300 m

Avalanche Summary

There was a widespread natural avalanche cycle ongoing during the stormy weather. Natural avalanche activity will likely decrease on Saturday with cool, dry weather. However, the potential exists for large avalanches on deeply buried weak layers. Low-angle terrain choices will be the key to managing this possibility.

There was a report of a natural size 2.5 avalanche running full path in the Dore River area on Thursday. A MIN report about this can be viewed here.

Several natural and human-triggered avalanches size 2-3.5 were reported on Tuesday near Valemount at alpine and treeline elevations. At least one of the very large human-triggered avalanches was initiated from a wind-loaded start zone at the top of a large alpine feature, propagated for hundreds of meters along a ridge, and ran to valley bottom. Thankfully the rider was able to escape unharmed.

On Tuesday, there was a fatal avalanche just outside of the region, northeast of Valemount in Swift Creek. The avalanche was a size 3.5 and is suspected to have failed on the late January persistent weak layer. The report can be found here.

Snowpack Summary

The region has received 40-80 cm of fresh snow in recent days. There are deep wind deposits in lee features at upper elevations. The recent snow sits on a persistent weak layer of facets that formed on the surface during the recent cold snap.

There is now 80-180 cm of snow above another persistent weak layer from early February which is composed of surface hoar. This layer is most prevalent at treeline and below treeline. On steep south-facing terrain, this layer may consist of facets on a sun crust. 

Yet another persistent weak layer from late January exists down 90-200 cm. There have been very few recent reports of avalanches or reactive test results on this layer, however, there have been several large avalanches on this layer in the neighboring North Rockies region recently, so it is worth keeping in mind.

Terrain and Travel

  • Use conservative route selection and resist venturing out into complex terrain.
  • Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Be especially cautious as you transition into wind affected terrain.
  • Brief periods of sun could quickly initiate natural avalanche activity.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm slabs may continue to be reactive, especially in wind-loaded areas at higher elevations, and on south facing slopes if the sun comes out with some power. Variable winds in recent days may mean that wind loading may be found on all aspects.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

40-80 cm of recent storm snow sits on a layer of weak, sugary facets. At upper elevations, the recent snow has been blown into reactive slabs in lee features. Recent avalanches have propagated widely and surprised riders.

Two more persistent weak layers are buried between 80-200 cm. These have not produced recent avalanches in the region that we know of, but have been responsible for several recent large avalanches in the neighboring North Rockies region, including two fatal avalanches in the past week.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Valid until: Feb 27th, 2021 4:00PM

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