Avalanche Forecast

Issued: Jan 21st, 2015 7:49AM

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

jfloyer, Avalanche Canada

Cariboos.

Avalanches continue to be triggered by light loads in this region. Forecast warm temperatures are likely to continue this trend.

Summary

Confidence

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

Weather Forecast

Thursday: Flurries. Freezing levels rising to around 1400 m. Ridgetop winds 40-50 km/h from the southwest. Friday: Light precipitation in the afternoon that might fall as rain or snow. Freezing levels between 1800 and 2200 m, ridgetop winds rising to 70 km/h from the southwest. Saturday: light to moderate rain/snow in the 5-10 mm/cm range with freezing levels rising to around 2000 m. strong southwesterly winds.

Avalanche Summary

Numerous natural and human-triggered avalanches were reported to have run during and after the most recent storm, up to and including Tuesday 20th, which is the most up-to-date info at the time of writing. Noteably, those that occurred on Tuesday 20th were larger than those that were reported during the storm, and more likely to have been human-triggered (although natural avalanches were also reported from Tuesday). One very large natural avalanche was reported from an east aspect at 2700 m. We do not have any details about the layer this avalanche ran on. Most avalanches

Snowpack Summary

Between 30 and 50cm of new snow fell during the most recent storm over the weekend. It was distributed by strong winds into deeper, more cohesive deposits in higher wind-exposed terrain. A weak layer that comprises feathery surface hoar crystals up to 15 mm lies directly below the recent storm snow and sits above a crust in many areas, especially on south-facing slopes. This "mid-January" weak layer is widespread and has been the main focus for most of the recent avalanche activity. It has also been consistently producing easy "pop" type failures in snowpack tests.The still problematic mid-December surface hoar/crust layer is now buried anywhere from 60 to 110cm below the surface and continues to produce clean shears at and below treeline. Avalanches were reported to have stepped down to this layer during and after the most recent storm cycle. Although it has become less likely to trigger, I'd continue to treat this layer with respect and suspicion, particularly in the 1700-1900 m elevation band. A release on this layer would have very high consequences.

Problems

Persistent Slabs

A weak layer comprising of feathery surface hoar crystals and on south aspects a crust is buried between 40 and 60 cm below the surface. This layer appears to be widely found in this region and many recent avalanches were triggered on it.

Choose well supported terrain without convexities.>Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 5

Wind Slabs

Winds were very strong during the last storm and created dense areas of wind slab in the lee of ridges and terrain breaks.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Today is not the day to set the record highmark.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Deep Persistent Slabs

A weak layer buried mid-December is still producing dangerous avalanches over a month after it was first buried. Particularly for slopes around treeline, there is a danger for a small avalanche to step down to this layer increasing the consequences.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Avoid open slopes and convex rolls at treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

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