Avalanche Forecast

Issued: Jan 20th, 2014 8:14AM

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

jfloyer, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

A couple of relatively small disturbances are expected to bring some freezing drizzle Tuesday night and Wednesday.Tuesday: Dry during the day, flurries in the evening. Ridgetop winds westerly 20-30 km/h. Alpine temperature reaching around 0C.Wednesday: Freezing Drizzle, turning to snow with 2-5cm expected. NW'ly winds gusting 20-30 km/h at ridgetop. Alpine temperatures around 0C.Thursday: Dry with a mixture of sun and cloud. Ridgetop winds increading to 40-50 km/h from the NW. Alpine temperatures around -4C.

Avalanche Summary

Recent explosives avalanche control in the region produced 2 size 3 slab avalanches which failed at ground level. They occurred on a northeast aspect, likely on upper elevation slopes.On Saturday, a size 2.5 deep persistent slab avalanche was reported to have failed naturally on a southeast facing slope at about 2300m. The avalanche failed on basal facets. On the same day, a snowmobiler triggered what appears to be at least a size 2 slab avalanche form a rocky alpine slope in the Allen Creek area. Little is known about the avalanche.

Snowpack Summary

Snowpack depths vary, but in general there is now 200 to 250cm of snow at tree line and as much as 300 cm in select places in the alpine. In some areas we're still dealing with a relatively thin snowpack. Roughly 100cm of well settled storm snow exists as a stubborn hard wind slab in many areas. Heavy wind scouring is reported to have occurred on many exposed windward slopes. Steep, sun exposed features are most likely seeing a daily melt-freeze cycle while surface hoar has been growing in shaded terrain. Below the recently formed storm slab you may find surface hoar buried around January 8th. Its distribution and reactivity seems highly variable. Where it exists, reactivity seems most likely below treeline.A basal facet/crust combo (weak sugary snow above and below a crust) near the ground is still a concern in some areas, and was the culprit with some of the very large recent avalanches. Likely triggers at this interface would include cornice fall, rapid temperature changes or thin spot triggering on an unsupported alpine or treeline elevation slope.

Problems

Deep Persistent Slabs

Although deep persistent slab avalanches have become less likely, the consequences of a release would be severe. Possible triggers include cornice fall, rapid temperature change or a heavy load over a thin spot.

Conditions have greatly improved, but be mindful that deep instabilities are still present.>Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Wind Slabs

Some operators are still expressing concern for wind slabs that were formed last week. Although they may have gained considerable strength, triggering may still be possible in steep, unsupported terrain.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 4

Valid until: Jan 21st, 2014 2:00PM