Avalanche Forecast

Archived

Mar 3rd, 2014–Mar 4th, 2014

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

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 possible, human triggered probable.

Regions

South Coast.

New snow and wind are building a new storm slab that may not bond well to the old surface of crusts and facetted crystals. Check out the Forecaster Blog for more information on the persistent weak layer.

Confidence

Fair - Forecast snowfall amounts are uncertain

Weather Forecast

Week disturbances embedded in the southwesterly flow continue to bring light- moderate precipitation amounts overnight Monday. Freezing levels will fall and there will be a lull between storms until Wednesday when things ramp up again. Lower snowfall amounts expected on the Duffy.Overnight Monday/ Tuesday: Snow amounts 16 cm. Alpine temperatures near -5.0. Ridgetop winds light-moderate from the SW.Wednesday: Snow amounts near 20 cm. Alpine temperatures near-5.0. Ridgetop winds light from the SW. Freezing levels rising to 1300 m.Thursday: Snow amounts near 5 cm. Alpine temperatures near -2.0. Ridgetop winds 10-30 km/hr from the SW, gusting to 75 km/hr. Freezing levels 1400 m.

Avalanche Summary

No new avalanche activity reported since the cold arctic air moved into the region. Forecast new snow and strong winds will likely continue to build new storm slab problems by morning.

Snowpack Summary

Up to 30 cm of new storm snow has buried the melt-freeze crusts and surface facets that developed over the past few cold days. Melt-freeze crusts formed on all aspects at lower elevations, and on all but high Northerly aspects. Last weeks very warm temperatures and periods of very strong solar radiation caused a great deal of settlement in the old storm slab above the early February weak layer. The February weak layer of crusts and facets has been reported to be rounding and bonding in areas where the old storm slab is 200 cm or deeper (there is between 2-3 metres of snow above the weak layer in the Coquihalla area). Shallow snow pack areas where the old storm slab is closer to a metre or less continue to give sudden planar shears in snow profile tests (there is about 60-80 cm above the weak layer in the Duffey Lake area). North aspects in the alpine may have had enough warming to settle the storm snow into a cohesive slab, but not enough to improve the weak layer bond. Big un-supported alpine North aspects are the most likely place to find a well preserved deeply buried February weak layer that may continue to allow for long propagations resulting in very large avalanches.

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.

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.