Avalanche Forecast

Issued: Jan 1st, 2016 8:22AM

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

triley, Avalanche Canada

Northwest Coastal.

Weak buried layers of surface hoar in the top 100 cm of the snowpack continue to be a concern for triggering slab avalanches.

Summary

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

No precipitation forecast until at least Monday night. Clear skies with warm air above about 1100 metres on Saturday and Sunday. Moderate to strong southerly upper winds over the weekend, unsure if this wind will be low enough to affect local terrain and transport loose snow. Monday starting off clear with cloud and southeast wind building during the day. Temperatures around -10 in the valleys of the south and closer to -20 in the north of the region.

Avalanche Summary

No new avalanches reported. Commercial operations cautioning new wind slabs at ridge lines developing with outflow winds.

Snowpack Summary

Solar radiation has started to affect the surface snow on southerly aspects, resulting in loose moist or wet releases and the beginnings of melt-freeze crusts overnight. The recent 25-40cm of storm snow continues to facet due to the cold temperatures, and new surface hoar has been reported on all aspects and at all elevations. The forecast temperature inversion looks like it will be strongest on Friday, and our uncertainty revolves around how much warmth upper elevations will receive. It is also unclear how storm slabs, especially those sitting on buried surface hoar layers (in the top 100 cm) will react to the warming. I suspect that outflow winds are transporting unconsolidated snow, and areas that are having or have received wind may continue to have wind slab problems. The winds have been variable across the region; Shames has reported very little wind and slightly west of there the wind effect has been widespread. The north of the region has been cold with temperatures around -20 in the valleys and alpine temperatures around -8 at 2000 metres. Watch for weak basal facets in colder and shallower snowpack areas.

Problems

Storm Slabs

Recent storm slabs may be triggered in areas where they have settled into slab due to warming, or from wind transport.

Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Persistent Slabs

This is the piece of the puzzle that won't let me drop the danger rating to LOW. The consequence of triggering a buried surface hoar weakness is high, although the likelihood of triggering seems to be getting lower.

Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>Carefully evaluate big terrain features by digging and testing on adjacent, safe slopes.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

Solar radiation and warm temperatures at higher elevations may result in loose moist or wet avalanches on steep solar aspects. Late in the day, westerly aspects may be the most likely areas for this type of avalanche activity.

Be alert to conditions that change with aspect, elevation and time of day.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Watch for clues, like sluffing off of cliffs, that the snowpack is warming up. >

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 2nd, 2016 2:00PM