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Avalanche Forecast

Archived

Jan 3rd, 2014–Jan 4th, 2014

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast.

Confidence

Fair - Due to the number of field observations

Weather Forecast

Overnight and Saturday: Mostly clear overnight with a mix of sun and cloud during the day. Cooler more seasonal temperatures with alpine lows about -10. Light to moderate Northwest winds and no precipitation.Sunday: Mix of sun and cloud with an area of warm air moving into alpine elevations pushed by moderate Southwest winds. Above freezing temperatures are expected in the Alpine.Monday: Continued warm air at higher elevations with light to moderate Southwest winds and no precipitation.

Avalanche Summary

No new natural avalanches reported during the storm due to poor visibility and travel conditions. One skier controlled size 2.0 avalanche that ran on mid december buried surface hoar in the Duffey Lake area.

Snowpack Summary

New snow is expected to be poorly bonded, especially on wind-loaded slopes. Snowpack depths vary greatly across the region with 180cm at treeline in the Cascades but only about 80cm in the Duffey Lake area, and terrain below treeline is still mostly below threshold for avalanche activity. In general the snowpack is shallow with a faceted and weak lower half, but also highly variable. Snowpack testing on a NW facing slope at 2150m in the Duffey Lake area on Thursday produced easy sudden planar compression test results, and a RB2, whole block release Rutschblock result down 27cm on the late-December surface hoar, this layer now has an additional 15-25 cms since the Thursday evening storm. Early season riding hazards such as rocks, stumps and logs are lurking below the surface at treeline elevations and below.

Problems

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.