Avalanche Forecast

Issued: Jan 4th, 2014 9:28AM

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

ghelgeson, Avalanche Canada

Cariboos.

While humans crave simplicity the current situation is anything but. The answer to the avalanche problem this weekend is staying conservative with terrain selection.

Summary

Confidence

Fair - Freezing levels are uncertain on Monday

Weather Forecast

A strong, stable northwesterly flow will prevail over the province while a strong upper ridge remains offshore. The ridge should weaken somewhat on Monday but will still protect the province from Pacific systems.Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light, Var. Strong NW at ridgetop.Monday: Freezing Level: Valley Bottom with chance of an Above Freezing Layer from 1500 2500m. Precip: Nil; Wind: Light NW, Extreme W at ridgetop.Tuesday: Freezing Level: Valley Bottom; Precip: Trace; Wind: Lht NW, Mod NW at ridgetop.

Avalanche Summary

Avalanches were running naturally and with explosive control to size 3.5 on Friday. The huge avalanches were mostly running on north through east facing slopes at upper elevations and involved the basal weaknesses near the ground. Wind slabs were running naturally on all aspects to size 2. Observations were limited on Friday, I suspect we'll learn more about this most recent avalanche cycle after operators have a chance to get out and see more terrain Saturday.

Snowpack Summary

Thursdays storm brought 25 - 60 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 surface hoar or facet layer that is down 100-150cm deep. The last week has brought around a meter of snow.Snowpack depths vary, but in general 175 cm of snow can be found at treeline, with 125-300 cm in the alpine. In some places we're still dealing with a relatively thin snowpack (thanks to a windy early season). The basal facet/crust combo (weak sugary snow above and below a crust) near the ground was active in Friday's avalanche cycle. This weakness may be difficult to trigger but if triggered, will result in very large, destructive avalanches.

Problems

Wind Slabs

New snow and fresh wind slabs lie over two different persistent weak layers in the upper meter of the snowpack. Wind exposed lee slopes at and above treeline will likely remain touchy Sunday.

Avoid freshly wind loaded features.>This problem will take extra time to settle out given the presence of persistent weak layers.>Choose well supported terrain without convexities.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Persistent Slabs

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

Choose well supported terrain without convexities and avoid slopes with a thin or variable snowpack.>Resist venturing out into complex terrain, even if you observe no obvious signs of unstable snow.>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 - Likely

Expected Size

3 - 6

Valid until: Jan 5th, 2014 2:00PM