Avalanche Forecast

Issued: Feb 10th, 2013 8:44AM

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

swerner, Avalanche Canada

Cariboos.

Summary

Confidence

Fair - Timing of incoming weather is uncertain on Tuesday

Weather Forecast

Monday: The pattern and flow starts changing today as the ridge move southward and a zonal flow sets up. An embedded cold front will move through the region bringing moderate NW winds and a trace of snow. Treeline temperatures will sit near -3 and freezing levels will be around 1100 m. Tuesday: The fast paced zonal flow will continue with a trough moving in from the West bringing moderate-strong SW winds and light-moderate snow accumulations. Treeline temperatures will be near -5 and freezing levels around 900 m.Wednesday: Another ridge is building bringing dryer conditions; especially for the short term. Ridgetop winds will be light from the West. Treeline temperatures -10 and freezing levels near 500 m falling to valley bottom overnight. Â

Avalanche Summary

On Saturday, a natural slab avalanche size 1.5 and several loose dry avalanches from steep terrain features were reported.

Snowpack Summary

Up to 40 cm of new snow is sitting on old wind slabs and recently buried weak layers. Old storm snow has settled into a dense slab that sits on a persistent weak interface deeper (40-80 cm down) in the snowpack. Buried crusts, surface hoar and facets are acting as those weak interfaces. Use extra caution on large open slopes, cutblocks and convex rolls at and below treeline where buried surface hoar may be preserved.Wind slabs continue to develop and stiffen on lee slopes and behind terrain features like ridgelines and ribs. Reverse loading may occur with changing winds. Unsuspecting slopes may catch you by surprise. The mid-pack is generally well settled and strong and the average snowpack depth at treeline elevations is near 200 cm. Cornices have grown and could threaten the slopes below.

Problems

Wind Slabs

Wind slabs continue to be a concern on lee slopes and behind terrain features like ridges and ribs. They could be triggered under the weight of a person. Looming cornices may threaten slopes below.

Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

New storm snow adds to the depth (50-80 cm) of the slab that is sitting on a variety of old surfaces comprising of surface hoar, crusts and facets. Persistent slabs may to be reactive to rider triggers and can be difficult to predict.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 5

Valid until: Feb 11th, 2013 2:00PM