Avalanche Forecast

Issued: Jan 3rd, 2014 9:12AM

The alpine rating is considerable, 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

Good

Weather Forecast

A strong northwesterly flow prevails as an upper ridge establishes itself offshore. Winds will be the most important feature to watch over the next 24 hours. Chance of precip on Monday evening.Saturday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Mod NW, Strong at ridgetop. Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light, Var. Strong SW at ridgetop.Monday: Freezing Level: 700m Precip: Nil; Wind: Strong SW, Extreme SW at ridgetop.

Avalanche Summary

Previous to Thursday's big storm avalanche activity was limited to fairly manageable wind/storm slabs to size 1/2. Within the last week we received reports of very large avalanches releasing deep within the snowpack (1 to 1.5m) in the Cariboos. I expect that the heavy snowfall associated with Thursday's storm will result in a large natural avalanche cycle. Check back tomorrow for more details.

Snowpack Summary

Thursdays storm brought 20 - 50 cm of snow to the region. This snow lies on top of old wind slabs, a buried rain crust that exists below 1600m and a couple buried weak layers (surface hoar or facets) that are down 100-150cm deep. I expect that there was a large natural avalanche cycle Thursday night. Expect to find touchy storm/wind slabs in exposed lee terrain at and above treeline that should persist through the weekend. The last week has brought around a meter of snow. Happy New Year. Snowpack depths vary, but in general 175 cm of snow can be found at treeline, with 125-250 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

The storm snow in conjunction with strong NW winds will likely continue to overload weak layers in the upper meter of the snowpack. Many slopes are primed for human triggered avalanches, particularly on exposed lee aspects at and above treeline.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

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

Whumpfing is direct evidence of a buried instability, if observed back off to lower angle terrain. >Use conservative route selection, stick to moderate angled terrain with low consequence.>Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 5

Deep Persistent Slabs

A weakness near the base of the snowpack may be more sensitive to human triggering as it adjusts to the new snow load. Avalanches running on the surface may step down to this layer resulting in very large and destructive avalanches.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 4th, 2014 2:00PM