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Avalanche Forecast

Archived

Feb 21st, 2014–Feb 22nd, 2014

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

Regions

South Columbia.

Don't let the improving weather fool you, conditions are very tricky and prime for human-triggered avalanches.The hazard will increase on south facing slopes on the first day of full sun.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

Some light disturbance is expected for Saturday and Sunday as a ridge of high pressure builds. Clear, cold, and dry conditions are expected for Monday once the ridge of high pressure has established. Saturday: A mix of sun and cloud, light scattered flurries 0-1cm, treeline temperatures around -10C, ridgetop winds light NWSunday: A mix of sun and cloud, light scattered flurries 0-2cm, treeline temperatures around -12C, ridgetop winds light W-NWMonday: Clear and sunny, treeline temperatures around -10C, ridgetop winds light NW

Avalanche Summary

Natural avalanche activity is generally decreasing now that the storm has ended but we are still receiving reports of natural activity. Conditions are ideal for human triggering right now and we have received numerous reports of skier triggered avalanches, many of which have released quite deep in the snowpack. Several of these avalanches were remotely triggered. On Thursday, 5 remotely triggered avalanches were reported in the South Columbia. The largest was a size 3, the farthest trigger was 150m away, and the deepest was 160cm.

Snowpack Summary

The recent ten-day storm has produced a cohesive slab that averages 1 m in thickness. This slab sits on a nasty persistent weak layer (surface hoar/facet/crust combo) that was formed during the preceding month of cold, dry weather. This weak layer is widespread at all elevations and aspects, and is creating problems even in previously skied terrain. Large settlements and whumpfs have been reported at all elevations. We have received numerous reports of remotely-triggered avalanches from as far as 200m away which indicates a high likelihood of large propagations within the weak layer. We expect touchy conditions to remain in place longer than we're normally accustomed to. Recent strong winds out of the SW through NW have created wind slabs on leeward features in wind exposed areas at treeline and in the alpine. In many areas, thick wind slabs may overlie the persistent weak layer creating conditions for very large avalanches.For the most part, the mid and lower snowpack are strong and well consolidated.

Problems

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.

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.