Avalanche Forecast

Issued: Jan 2nd, 2014 9:07AM

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

ghelgeson, Avalanche Canada

Cariboos.

Summary

Confidence

Fair

Weather Forecast

Precipitation will continue through the night tapering off before dawn. Storm totals should be in the 20 30 cm range. The freezing level drops after the storm and a ridge of high pressure looks to dominate for the foreseeable future.Thursday Night: Freezing Level: 1000m; Precip 5/10mm - 5/15cmFriday: Freezing Level: 700m Precip: Nil; Wind: Mod NWSaturday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Mod NW Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light, Var.(Forecasted wind speeds are at 2000m)

Avalanche Summary

Reports of several natural and skier triggered avalanches on Tuesday. Natural avalanches up to size 2 in wind loaded features at treeline on various aspects. Ski cuts and skier accidentals size 1 from small pockets of wind loaded terrain features at treeline. Most of the recent reported activity has been limited to the storm snow and wind loading with depths varying from 20-40cm. However, there have been reports from last weekend of very large avalanches releasing deep within the snowpack (1 to 1.5m) in the Cariboos. Also on Tuesday, several very large, deep released avalanches occurred in the Selkirk Mountains. Continuing with the trend, a size 2.5 natural was observed on a steep NE face Wednesday. The potential in the Cariboos for very large, deep avalanches remains a major concern, especially with the additional loading on Thursday evening.

Snowpack Summary

Around 75 cm of new snow has fallen in the last week. Recent mild temperatures have caused substantial settlement of this new snow. This has created a slab around 20-40cm thick which may overlie softer snow creating an upside-down condition in the upper snowpack. Areas of the region have seen moderate to strong winds from the SW-NW resulting in variable wind slabs. Expect to find touchy wind slabs in exposed lee terrain at and above treeline. A buried rain crust exists below 1600 m and a couple buried weak layers (surface hoar or facets) are now down 80-100 cm deep. Snowpack depths vary, but in general 150 cm of snow can be found at treeline, with 100-200 cm in the alpine. In many places we're still dealing with a relatively thin snowpack (thanks to a windy early season) so there's not a whole lot of snow between riders and the sugary snow (facets) near the ground. The basal facet/crust combo has been recently active in parts of the region and continues to give easy to moderate results in snowpack tests. This basal weakness may be difficult to trigger but if triggered, may result in very large, destructive avalanches.

Problems

Storm Slabs

New snow and wind will likely overload the upper snowpack on a variety of aspects, particularly those on lee aspects in exposed areas. Although snowfall will taper Friday, the snowpack will likely be primed for human triggered avalanches.

Avoid freshly wind loaded features.>Avoid complex terrain and be aware of what is above you at all times.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

The presence of buried weak layers increases the likelihood of larger avalanches that could release to a depth of a metre or even more. The distribution and reactivity of persistent weak layers is highly complex at the present time.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Whumpfing is direct evidence of a buried instability, if observed back off to lower angle terrain. >

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 5

Deep Persistent Slabs

A weakness near the base of the snowpack could be triggered by continued loading or by riders in thin snowpack areas. Smaller avalanches have the potential to step down to this layer which would greatly increase the consequences of an avalanche.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid rock outcroppings, steep convexities and anywhere the snowpack feels thinner than average.>

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Jan 3rd, 2014 2:00PM