Avalanche Forecast

Issued: Jan 28th, 2017 3:27PM

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

istorm, Avalanche Canada

Cariboos.

Several parties have triggered large avalanches with burials. Conservative terrain selection remains critical.

Summary

Confidence

Moderate - Wind effect is extremely variable

Weather Forecast

Wind & snow in the forecast.SUNDAY: 10 to 25 cm of fresh snow, strong SW winds and freezing levels dropping throughout the day to valley bottoms.MONDAY: Mixed sun and cloud, isolated light flurries possible, moderate westerly winds, 5 to 10 degrees colder than Sunday.TUESDAY: Clear, cold, dry, light northerly wind.

Avalanche Summary

Over the pat week there were several large human triggered slides. At least 10 close calls were reported to us and several of these avalanches involved multiple people being buried. Four of these avalanches were in the Allen Creek riding area, one was in the Monashees near Blue River, on was on Mt Bell near McBride. These avalanches all released on or stepped down to the mid-December weak layer down 1-1.5 m in the snowpack. Check out the MIN posts and a great video on the Frozen Pirate Snow Services Facebook page for more details. Also reported on Thursday were a few natural avalanches up to Size 2 triggered by direct sun exposure.Looking forward, the incoming storm will form windslabs on downwind side of ridges & ribs, as well as crossloaded slopes. If more than 25 or 30 cm arrives, a more general (widespread) storm slab problem could develop on steep slopes. Remeber, even as surface instabilities gain strength, deeper destructive persistent slab avalanches failing on the mid-December weak layer will remain a serious concern for the foreseeable future.

Snowpack Summary

Fifty to 70 cm of recent snow covers the mid-January snow surface which includes buried surface hoar in sheltered areas, and/or widespread facets. This slab is particularly touchy where where the buried surface hoar is preserved. Strong southwest winds during the storm have formed wind slabs in leeward terrain features. A second surface hoar/facet weakness buried mid-December, is now found down 50 cm in shallow snowpack areas, or as much as 1.5 m in deeper snowpack areas. This layer woke up during the last storm and has remained reactive to human triggers. This December weakness is responsible for several large human-triggered avalanches, including some with multiple burials, and this sensitivity is expected to continue for the foreseeable future.For more information, check out this video of our field team testing the snowpack near Barkerville: https://vimeo.com/201318688

Problems

Persistent Slabs

The persistent weakness buried mid-December has been responsible for several large human-triggered slab avalanches and subsequent burials over the past couple of days. These deeper weaknesses can with nasty consequences.

Avoid shallow snowpack areas where triggering is more likely.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Wind Slabs

Fresh touchy wind slabs are expected on the downwind side of ridges, ribs. If more than 25 or 30 cm arrives, a more widespread storm slab problem could develop on steep slopes. Buried surface hoar may make these slabs particularly touchy.

Avoid areas where the surface snow feels stiff or slabby.Watch for signs of instability such as whumpfing, or cracking. Use caution in lee areas. Recent wind loading has created wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Valid until: Jan 29th, 2017 2:00PM