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Avalanche Forecast

Archived

Mar 5th, 2014–Mar 6th, 2014

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 possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

South Coast.

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Tonight and Thursday: Moderate to locally heavy snowfall – 5-15 cm overnight and another 10-25 cm during the day. The freezing level is around 1300-1500 m. Winds are moderate to strong from the SW. Friday: Mainly cloudy with flurries. The freezing level remains near 1500 m and winds are moderate from the W-SW.  Friday night and Saturday: Moderate to heavy precipitation. The freezing level climbs to 1800 m and winds are strong from the SW.

Avalanche Summary

Several size 2-2.5 storm slab avalanches were reported in the Coquihalla on Tuesday. Most of these were from north to east aspects and likely released on the early March melt-freeze crust. A couple natural wind slab avalanches up to size 2 were also reported from the South Chilcotins.

Snowpack Summary

Coquihalla and south: Strong southerly winds have redistributed some of the new snow and formed wind slabs in exposed lee and cross-loaded terrain. Around 60 cm of storm snow has fallen in the past few days. This new snow may feel upside down due to warming temperatures, and seems to be bonding poorly to the early March melt-freeze crust. The mid February weak layer of crusts and facets, now down over 200 cm deep, has been reported to be rounding and bonding. Duffey Lake and north: New dense wind slabs are likely in exposed NW-E facing terrain and cross-loaded features. The early March melt-freeze crust is down 30-45 cm everywhere expect high north aspects. The mid Feb weak layer is generally down 60-120 cm depending on orientation to wind. Recent snowpack tests continue to give pops shears where this layer is less than 100 cm deep. Deeply buried weak layers of facets and depth hoar remain a concern on high alpine slopes with thin or variable snow cover.

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.