Avalanche Forecast

Issued: Jan 2nd, 2015 7:28AM

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

Peter, Avalanche Canada

South Coast.

We are on the verge of another sharp transition from cold and dry to wet and mild. Avalanche danger is expected to start to rise on Sunday.

Summary

Confidence

Fair - Freezing levels are uncertain on Monday

Weather Forecast

Synopsis: On Saturday we should see a brief â€˜calm before the stormâ€™ with mainly cloudy skies and a chance of flurries. The freezing level is at valley bottom and ridge winds are generally light. A frontal system reaches the South Coast by Sunday morning dumping 10-20 cm of snow throughout the day. The freezing level remains at valley bottom and winds increase to moderate or strong from the SW. Moderate to heavy precipitation continues on Monday but temperatures should start to rise, possibly to 2000 m by the end of the day or overnight.

Avalanche Summary

Avalanche activity over the past couple days has mostly been loose wet sluffs from solar radiation and warm alpine temperatures. Earlier in the week there were numerous reports of natural and rider triggered wind slabs up to size 2.5 from southerly aspects as a result of outflow winds.

Snowpack Summary

The current snow surface varies significantly and includes wind affected surfaces in exposed alpine and treeline terrain, a sun crust on steep solar aspects, dry faceted powder in sheltered shady terrain, and pockets of surface hoar (mainly below treeline). Older wind slabs are still lurking on south facing slopes near ridge tops from last weeks outflow winds. The mid-December SH layer may be present in specific areas (sheltered, shady, near open water sources) down 40-70 cm. On Thursday one observer found this layer down 55 cm on a N aspect at 1700 m. Snowpack tests gave easy or moderate "drops" results. Below 2000 m and buried 60-80 cm deep you might find a crust with facets or mixed forms above or below.

Problems

Wind Slabs

Previous outflow winds created dense or hard wind slabs on exposed south-facing slopes. Light snow and westerly winds could form pockets of fresh wind slab on east-facing slopes, or hide the older hard wind slabs.

Watch for areas of hard wind slab in steep south-facing alpine features.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Several persistent weak layers exist in the upper to middle snowpack. It might take a large load (like a cornice fall), major weather input (heavy rain or snow), or a rider hitting the sweet spot to trigger this problem.

Avoid convexities or areas with a thin or variable snowpack where triggering is more likely.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Jan 3rd, 2015 2:00PM