Avalanche Forecast

Issued: Jan 4th, 2017 4:34PM

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

Avalanche Canada mgrist, Avalanche Canada

Cold north winds have been blowing. Areas with wind slabs (south through northwest aspects) may have elevated danger.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

The arctic outbreak continues with cold temperatures and no snow until Saturday afternoon at the earliest.THURSDAY: A mix of sun and cloud. Wind light southwest. Temperatures between -13 and -24 Celcius. No precipitation.FRIDAY: Cloudy with sunny periods. Winds southerly 5-15 km/h. Temperatures between -12 and -22 Celcius. No precipitation.SATURDAY: Increasing clouds in the afternoon with a slight chance of flurries. Winds light southeasterly 5-15 km/h. Temperatures between -12 and -20 Celcius.

Avalanche Summary

We've had reports of several skier-triggered windslabs (Size 1.5-2) yesterday in the backcountry near Nelson, and some natural activity the day before. Aspects were southwest through north at treeline and in the alpine.

Snowpack Summary

The snow from last week (30-60 cm) has been exposed to east through northerly winds during this cold clear period. In many areas "reverse loading" occurred, causing windslabs to form and giving sudden planar results in snowpack tests. The most recent snow sits over a weak layer buried on Boxing Day that was initially reactive but now appears to have gained strength.  Slightly lower in the snowpack is an interface buried mid-December, now down 40-100 cm. This layer appears to be well bonded in many parts of the region but was reactive for a while last week west of Trail and Castlegar where preserved surface hoar was thought to be responsible for four small (but surprising) skier trigger avalanches. It will be important to continue to monitor this layer for further signs of reactivity.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs have been forming on mainly southwest to north aspects behind exposed terrain features. Slabs found on south aspect slopes could become more unstable when the sun is out.
Use caution in lee areas. Recent wind loading has created wind slabs.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 5th, 2017 2:00PM

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