Avalanche Forecast

Issued: Dec 29th, 2013 7:49AM

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

Peter, Avalanche Canada

Cariboos.

Summary

Confidence

Poor - Intensity of incoming weather systems is uncertain

Weather Forecast

Tonight and Monday: Periods of snow, heaviest on the western slopes – 15-25 cm. The freezing level is near valley bottom and winds are moderate to strong from the W-NW. Tuesday: Cloudy with possible sunny breaks and a chance of flurries. The freezing level is near valley bottom. Winds are light to moderate from the NW.Wednesday: A mix of sun and clouds with light snow possible late in the day. The freezing level is at valley bottom.

Avalanche Summary

Several snowmobile triggered slab avalanches up to size 2 were reported in the Cariboos near Valemount. Most of these involved the most recent storm snow, but it's possible a couple larger events stepped down to deeper persistent weaknesses. Also, a few natural size 2-3 slab avalanches were reported on Saturday from steep NW-NE aspects in the alpine in other areas. One event (size 3) appeared to fail on a deeper persistent weakness in the snowpack. Similar activity is expected to continue with additional loading from snow and wind on Sunday and Monday.

Snowpack Summary

Another 10-15 cm of snow fell on Saturday night bring storm totals to around 50 cm in some areas. Winds have been generally moderate to strong from the SW-NW and temperatures have fluctuated. Expect to find touchy wind slabs in exposed lee terrain at and above treeline, and buried rain crusts below 1600 m. A couple buried weak layers (surface hoar or facets) are now down 80-100 cm deep. Recent snowpack test results on these layers vary, but some are showing this layer "pop" with easy to medium loads, indicating a potential for human triggering.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.

Problems

Storm Slabs

Storm slabs and wind slabs continue to build and may release naturally with more load or from the weight of a rider. Watch for touchy wind slabs on exposed north through southeast facing slopes and cross-loaded features well into treeline.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Stick to simple terrain and be aware of what is above you at all times.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 4

Persistent Slabs

Several persistent weaknesses exist in the upper and mid-snowpack and could be triggered by the weight of a skier or rider or from continued loading from snow and wind.

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 - Likely

Expected Size

2 - 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.

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

2 - 6

Valid until: Dec 30th, 2013 2:00PM