Avalanche Forecast

Issued: Dec 30th, 2016 4:59PM

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

Avalanche Canada rbuhler, Avalanche Canada

Watch for signs that the recent storm snow is still reactive to triggering. Slabs will be most reactive in wind loaded terrain features.

Summary

Confidence

Low - Due to the number of field observations on Friday

Weather Forecast

Light snowfall is expected for Saturday afternoon with 2-4 cm expected in the Duffy and up to 10 cm expected for the Coquihalla. Alpine wind is forecast to be moderate to strong from the northwest and treeline temperatures are expected to be around -10C. A mix of sun and cloud is forecast for Sunday with moderate to strong northeast winds and treeline temperatures around -15C. Sunny conditions are currently forecast for Monday with moderate outflow winds continuing and treeline temperatures falling close to -20C.

Avalanche Summary

On Thursday during the storm, natural storm slabs up to size 2.5 were observed in the Duffey Lake area. These avalanches were reported to be releasing from steep terrain features, gullies, and slopes exposed to cross loading from wind. On Saturday, storm slabs remain an isolated concern but wind loaded areas are expected to be the main area of concern. Strong alpine winds were from the south at the start of the storm on Thursday and were from the west by the end of the storm. Winds on Saturday are now coming from the north. As a result, wind slabs should be expected on all aspects in wind affected terrain.

Snowpack Summary

25-45 cm of low density snow accumulated during the storm on Thursday. This brings the total storm snow amounts since Monday to 60-80 cm. Below the new snow from this week lies the Boxing Day interface which consisted of wind affected surfaces, faceted (sugary) snow, or surface hoar. The surface hoar has been observed up to 5 mm in size in the Duffey Lake area. A thin crust may also exist in the upper snowpack and was reported around Coquihalla area last weekend. Recent strong winds have been from a variety of directions and have been loading leeward and cross loaded features in wind exposed terrain. The mid-December interface is now down over 1 m and is generally considered to be stable in the region.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs from Thursday may still be reactive to human triggering on Saturday, especially in wind loaded terrain and on steep slopes. Winds have recently changed direction and slabs should be expected on all aspects in wind exposed terrain.
Give the new snow time to settle and stabilize before pushing into big terrain.Avoid freshly wind loaded features.Recent winds have changed direction. Watch for wind slabs on all aspects.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Dec 31st, 2016 2:00PM

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