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Avalanche Forecast

Archived

Dec 14th, 2013–Dec 15th, 2013

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

Regions

South Columbia.

Confidence

Fair - Intensity of incoming weather systems is uncertain

Weather Forecast

Overnight Saturday and Sunday: Moderate snowfall becoming light on Sunday / Strong to extreme westerly winds / Freezing level at 1100mMonday: Flurries / Moderate to strong Westerly winds / Freezing level at 600mTuesday: Heavy snowfall / Moderate southerly winds with extreme gusts / Freezing level at 1200m

Avalanche Summary

Several natural slab avalanches to size 2.5 occurred in the Selkirks on Friday. These avalanches occurred on various aspects in wind-affected terrain.I would expect more slab avalanche activity in the wake of snow, wind and moderate temperatures on Saturday.

Snowpack Summary

Since last week's cold snap daily snowfall amounts have generally been in the moderate range. Although accumulations have been variable, roughly 60cm of snow now overlies the weak faceted crystals or small surface hoar which formed during the cold weather. On lower elevation slopes rising temperatures are expected to have enhanced the slab properties creating a more reactive "upside-down" snowpack. Moderate to strong southwest winds have created wind slabs in exposed high elevation terrain.As of late there has been no reported activity on the late-November interface which consists of sun crusts on steep south facing slopes and surface hoar in sheltered areas. This layer, buried between 60-80cm below the surface, is generally considered to be "stubborn" to trigger; however, avalanches at this interface could have nasty consequences.Weaknesses towards the base of the snowpack are mostly thought to be dormant at this time.

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.