Avalanche Forecast

Issued: Jan 8th, 2017 4:16PM

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

jsmith, Avalanche Canada

Northwest Inland.

Weak, sugary snow at the bottom of the snowpack remains a primary concern. This is especially true in large, steep, and rocky alpine features with variable snowpack depths.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY: Mix of sun and cloud, strong to extreme easterly ridgetop winds, and temperatures around -20 C.TUESDAY: Mostly sunny with cloudy periods, moderate to strong northeasterly ridgetop winds, and temperatures around -15 C.WEDNESDAY: Mostly sunny with cloudy periods, moderate northeasterly ridgetop winds, and temperatures around -10 C.

Avalanche Summary

Over the past week there have been a couple natural deep persistent avalanches to size 3.5. These are large, destructive avalanches that failed on sugary facets at the bottom of the snowpack and ran long distances.

Snowpack Summary

10-20 cm of recent snow with northerly winds have likely created fresh wind slabs sitting on top buried surface hoar and/or facets. Snow depth at treeline varies from about 1 m in most areas to 2 m in deeper snowpack areas in the south and west of the region, and up to 250 cm in the alpine. The shallow snowpack areas mostly consist of weak facetted or sugary grains beneath hard slabs. These hard slabs may produce surprisingly long fractures resulting in large avalanches, and in some instances they may step down to weak snow crystals near or at the ground. In addition to the facets, a thick layer of buried surface hoar may be found 30-40 cm below the surface. There is another persistent weakness that formed during the early December cold snap which is now about 50-70 cm deep. A crust from mid-November may be lurking close to the ground nestled in amongst the facets.

Problems

Deep Persistent Slabs

This is a low probability, high consequence scenario and requires a conservative approach to larger terrain features. Avoid likely trigger spots such as steep and rocky areas with a shallow snowpack.

Avoid steep convexities or areas with a thin or variable snowpack.Be aware of the potential for full depth avalanches due to weak layers at the base of the snowpack.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Forecast strong to extreme easterly winds may form wind slabs in unusual places such as open areas below treeline.

Avoid areas where the snow feels stiff or slabby.Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 9th, 2017 2:00PM