Avalanche Forecast

Issued: Jan 21st, 2015 8:49AM

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

Avalanche Canada rbuhler, Avalanche Canada

The deep mid-Dec layer remains reactive and there have been several avalanches in the last few days. Use a conservative approach and assess conditions before committing to big terrain features.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Light flurries are possible on Thursday morning. Freezing levels are expected to be around 1000m and alpine winds should remain light. Friday will be unsettled in advance of a frontal system which is expected to arrive in the evening. Friday should be mostly cloudy with freezing levels around 1000m and light alpine winds. Around 5mm is expected Friday night with moderate SW winds. On Saturday, freezing levels are forecast to climb to around 2500m. Another 5-10mm are expected for Saturday.

Avalanche Summary

On Tuesday, one natural avalanche was reported. A cornice broke off and triggered a deep slab avalanche on the mid-Dec layer. Three skier triggered avalanches were also reported and these all released on the mid-Dec surface hoar layer. Depths varied from 30cm to 100cm with typical values around 70cm. On Monday, a natural size 1.5 storm slab was reported. This released down 25-40cm on the mid-Jan surface hoar. Also reported were a few ski cuts and explosive triggered avalanches. These were typically size 1.5-2 and released on the mid-Jan layer. These occurred on north through east aspects between 1900 and 2100m. Natural avalanche activity is generally not expected on Wednesday but remains possible in isolated areas such as steep sun exposed slopes or wind loaded areas. Human-triggering is likely in wind loaded areas and steep terrain features, especially where surface hoar underlies the recent storm snow.

Snowpack Summary

Around 30cm of snow sits on the mid-Jan surface hoar layer. In many places the surface hoar sits above a thin crust that can be found up to about 1900m on north aspects and all the way to ridgeline on south aspects. Strong SW winds during the storm loaded leeward features and the persistent slab may be 50-60cm thick in wind loaded areas (typically north through east aspects). A deeper crust/surface hoar combo buried in mid-December continues to be a concern. This layer can typically be found down 70-100cm. The reactivity of this deep persistent weak layer appears to have become isolated but still has the potential for large, destructive avalanches in some areas. The layer has been the most reactive at and just below treeline.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
The mid-Dec weak layer should remain on your radar as it still has the potential to produce large avalanches. Smaller avalanches or cornice falls have the potential to trigger this deeper weakness.
Use extra caution on open slopes and convex rolls at and just below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

3 - 6

Persistent Slabs

An icon showing Persistent Slabs
~30cm of snow sits on the widespread mid-Jan surface hoar/crust layer. In wind loaded areas, the slab may be around 50cm thick. The reactivity of the slab may not have reached full potential in many areas but is expected to with warming and new load.
Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Jan 22nd, 2015 2:00PM

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