Avalanche Forecast

Archived

Mar 4th, 2012–Mar 5th, 2012

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

South Coast.

Confidence

Fair - Forecast snowfall amounts are uncertain on Monday

Weather Forecast

The next pulse of moisture looks like it will bring heavier precipitation. Expect about 20-30 cm of snow combined with strong southwest winds and a freezing level near 1600 metres on Sunday night. Snow should taper off by Monday morning with a chance of convective flurries Monday afternoon. The freezing level should drop down to valley bottom by Monday as the wind clocks to the northwest. Tuesday morning should be dry and cool with valley temperatures dropping down to about -10.0 and light northwest winds. Cloudy skies with moderate northwest winds are forecast for Wednesday. The freezing level should rise to about 1200 metres.

Avalanche Summary

Reports of a natural moist avalanche cycle in the Coquihalla up to size 3.0 on Saturday. There was a skier accidental avalanche size 2.0 off Vantage Ridge in the Cerise Creek area on Saturday from a NE aspect at 2000 metres that failed down about 20-30 cm.

Snowpack Summary

New windslabs and a storm slab are developing from new snow and strong southwesterly winds. There has been about 40 cm in the Coquihalla and 25cm in the Duffey Lake area in the past few days. A weak layer of buried stellar crystals and/or decomposed and fragmented crystals is now buried by about 50 cm of storm snow. This layer has been giving moderate shears in snowpack tests a few days ago. Warm temperatures have created a moist slab up to about 1700 metres that is sliding naturally and with light additional loads in the Coquihalla area. Moderate shears down 40cm that are showing a sudden planar character on well preserved precipitation particles on a NE aspect at 1900 metres in the Duffey Lake area. Easy shears down 5cm on sun crust on a south-southwest aspect at 1950 metres in the Duffey; storm snow forecast for Sunday night may overload this layer.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.